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EPITHELIAL TISSUE EPITHELIAL TISSUE Objectives: To grasp the structure of simple squamous epithelium, simple cuboidal epithelium, simple columnar epithelium, stratified squamous epithelium. To understand the structure of transitional epithelium. Slide 58 Simple Squamous Epithelium ( Mesothelium ) AgNO3 This is a surface view of a frog’s mesentery. Choose thinner place to observe, the cell limits are stained black with AgNO 3. The individual cell has hexagonal or irregular wavy outlines, and each contains a nucleus which is not shown in this slide. Slide 32 Simple Squamous Epithelium ( Mesothelium ) H.E. This is the cross section of colon. In the outmost layer, mesothelium which likes a line is present. The mesothelial cells are fusiform with deep-stained ovoid nuclei in centre. The outlines of the cells are not clear. Slide 42 Simple Cuboidal Epithelium ( Thyroid ) H.E. In this section, there are many follicles in various sizes, which are composed of simple cuboidal epithelium. In the lumen 1 EPITHELIAL TISSUE of the follicle contains red colored homogenous colloid. The epithelial cells appear as a row of square profiles with round nuclei in centre. Slide 29 Simple Columnar Epithelium ( duodenum ) H.E. This is a section of the duodenum. There are many intestinal villi which are finger-like projections of mucosa. The surface of villi are covered by the simple columnar epithelium. The epithelial cells are mainly composed of columnar cells which are the tall rectangle cells with elongated nuclei occupying the base of these cells. Among the columnar cells you can find some Goblet cells with a deep-stained and triangle-shaped nucleus. Slide 5 Pseudostratified Ciliated Columnar Epithelium (Trachea) H.E. This is a ring of transversally sectioned treachea with large central lumen. The thin bluish-purple colored layer lining the luminal surface is pseudostratified ciliated columnar epithelium. This epithelium appears as multilayered because of the presence of nuclei at two levels. However all cells rest on a pink basement membrane which is located between epithelium and connective tissue, but some of them do not extend to the luminal surface.The epithelium consists of 4 type cells: Columnar cells are tall with ovoid nuclei at high level. Their 2 EPITHELIAL TISSUE free surface possesses regular cilia. Basal cells are smallest and arranged in basal portion of this epithelium. They are pyramidal in shape,but their apices do not reach the free surface of the epithelium, their nuclei are round and situate in the basal portion of the cells. Fusiform cells are spindle in shape with oval nuclei at the mid portion of the cells. Goblet cells can be seen among the columnar cells. Their apical portion enlarges like a pale round vacuole due to dissolution of secretory granules during section preparation. Their narrow basal portion contains deep blue-stained nucleus which is compressed by apical secretion and become triangular in form. Slide 4 Stratified Squamous Epithelium ( Esophagus ) H.E. On the lumen side of the esophagus, you will be able to find nonkeratinized stratified squamous epithelium. The epithelium sheet is thick, which consists of many layers of epithelial cells of different sizes and shapes but these epithelial cells change their shape gradually from the basal layer to the superficial layer. At the basal surface, connective tissue projects toward the epithelium, forms many pyramidal papillae. A layer of dark stained cells surrounding the papillae is the basal layer of epithelium. Basal layer contains one layers of small, cuboid or low columnar epithelial cells which rest on the basement membrane. 3 EPITHELIAL TISSUE Mid layer is composed of several layers of large polyhedral cells with clear boundary and ovoid nuclei. Superficial layer is made of several layers of flat cells. The cells closely overlap each other. Both the cells and their nuclei are very flat. Slide 66 Transitional Epithelium ( Bladder ) H.E. This is a section of a contracted bladder. This special stratified epithelium typifies the lining of urinary tract. Unlike the previous stratified epithelia, however, the surface layer of cells characteristically project into the lumen, giving them the name “dome cells”. Cell outlines are less distinct in this epithelium, and the cells are variably flattened, depending on the state ofdistension. It is a layer of large, dome-shape cuboidal or rectangular cells with deep-acidophilic cytoplasm. Occasionally contains two nuclei. The intermediate layer is composed of one to several layers of irregular polyhedral cells and pear-shaped cells located above the polyhedral cells.Pear-shaped cells are inverted-pear in shape with its broad base upward toward the domes. The deepest layer of cells consists of one layer of cuboid cells. The full and distended bladder shows less layers of cells, and the cells are more flattened. 4 CONNECTIVE TISSUE PROPER CONNECTIVE TISSUE PROPER Objectives: To grasp the spread and section of loose connective tissue (fundus of stomach). To understand reticular connective tissue (lymph node), dense connective tissue and adipose tissue. Slide 6 Loose Connective ( Areolar ) Tissue Mesenterium in Spread Preparation. Orcein or Aldehyde Fuchsin Stain. This preparation was made by ripping off a small portion of the mesentery spread with previous injection of trypan blue and spreading it out gently on a slide before fixation. Choose a thin and distinct area of the tissue for observation. Two types of fibers can be distinguished: Collagen fibers: --wavy stranded bundles of fiber of varied thickness run in all directions. They are reddish in color. These bundles of fiber branch by subdivision of the strands (i.e. by separation of small collagen fibers from one another). Elastic fibers: --stain in purple or dark red. These normally appear straight but where breakage has occured may appear wavy due to elastic recoil. Note unlike collagen fibers, it forms single structures which branch directly at acute angles. 5 CONNECTIVE TISSUE PROPER Among these fibers at least two types of cells, macrophages and mast cells can be seen: Macrophages are irregularly shaped cells with small rounded nuclei and engulf a lot of foreign particular matter such as trypan blue granules in the cytoplasm. Mast cells often lie along the course of the blood vessels, and run in groups. They are round or ovoid with small rounded nuclei, their cytoplasm contains a large amount of blue colour granules. Slide 3 Loose Connective Tissue ( Stomach ) H.E. The portion of gastric fundus stained lightly is loose connective tissue. It occupies the bluish-purple gastric mucosa above and red muscular layer below. Find and locate the loose connective tissue area in which fibers are loosely arranged and variously sectioned, the collagenous fibers are numerous, pinkish, while elastic fibers are scant and in brilliant red but hardly distinguished. Among fibers, many cells containing bluish-purple ovoid or fusiform nuclei are fibroblasts. Ground substance is lost during preparation and only empty spaces left between fibers and cells. Within the loose connective tissue, many vessels can be seen. 6 CONNECTIVE TISSUE PROPER Slide 8 Dense Connective Tissue ( Lymph node ) H.E. Lymph node is surrounded by a capsule of dense connective tissue.The pink-staining collagen fibers are in tightly packed bundles parallel to the longitudinal axis of the node and the cells between them are flattened to a fusiform with little cytoplasm. Slide 19 Adipose Tissue ( Skin ) H.E. This is the section of skin. Skin is composed of two parts, the outer epidermis and inner dermis. Beneath the dermis is the hypodermis, containing many fat cells. Fat cells are arranged in groups and appear vacuolated cytoplasm due to the drops of lipid being dissolved during section preparation. The nuclei are small flattened in periphery. Slide 7 Reticular Tissue ( Lymph node ) AgNO3 This is the section of lymph node. The reticular fibers are stained black with AgNO3 ,showing short branches and network. The reticular cells are lightly yellow with some processes. 7 CARTILAGE CARTILAGE Objective: To grasp the morphological feature of hyaline cartilage (Trachea). To understand the morphological feature of elastic cartilage and fibrocartilage. Slide 5 Hyaline Cartilage ( Trachea ) H.E. This slide is a cross-section through the trache. Locate the tracheal lumen and look at the blue-stained hyaline cartilage deep to the epithelium. The cartilage is covered by a layer of dense connective tissue named perichondrium. The inner layer of the perichondrium is rich in cells which can differentiate directly into chondroblasts, while the outer layer of the perichondrium is rich in fibers. The hyaline cartilage consists of a rather dense amorphous ground matrix in which are embedded groups of prominent rounded cartilage cells (chondrocytes). The cells are surrounded by a cartilagious capsule. At the periphery of hyaline cartilage, the chondrocytes have elliptic shape, with their long axis parallel to the surface. They are round and may appear in groups . The 8 CARTILAGE matrix immediately around each group is rich in chondroitin sulfate and may be stained more deeply than the remainder, in living tissue, the chondrocytes fill the lacunae completely, the cavities (lacunae) sometime appear empty since the cytoplasm of chondrocyte tends to collapse after fixation. Note that the cartilage is devoid of blood vessels. Slide 9 Elastic Cartilage ( External Ear ) Orcein The ear pinna is covered by skin , elastic cartilage located in the center of the pinna. The cells are quite similar to those of hyaline cartilage. Note the dense network of blue staining elastic fibers which fill the matrix between lacunae containing the chondrocytes. The fibers are thick and rich in number in the center of cartilage, while the fibers settled peripherally are fine, sparse and continuous with those of perichondrium. Slide 10 Fibrocartilage ( Intervertebral Disc ) Mallory Collagen fibers are the major constituent of this matrix. They reveal as thick and compact collegenous bundles with blue colour, paralleling or interweaving with one another. The red-stained chondrocytes are ovoid in shape, small in size and arranged in column. Small amount of matrix can be seen between the collagenous bundles. 9 BONE BONE Objective: To grasp the structure of Haversian system. Slide 11 Compact Bone ( Ground Bone ) Dialia Violet Calcified bone is too hard to be sectioned on a microtome. This section was prepared by cutting thin slices in transverse section with a saw and grinding these down to the required thickness with abrasives. The preparation is stained and the organic material is not preserved . Such sections show the layered calcified intercellular matrix but not the cellular structure or other organic material. Harversian system: You should be able to see the outlines of irregular Harversian Systems. They consist of: 1) A centrally located Harversian canal in which vessels, lymphatics, nerves and connective tissue are located at living period, the empty space, which are filled with debris and dye stain appear purple. 2) A series of concentrically arranged lamellae are the Harversian lamellae. The bone lamellae are arranged in concentric layers around a central Harversian canal. The lamellae represent an alternation of dark and bright lamellae because the 10 BONE fibers in different lamellae are different in orientation. The bone lamellae fluctuate from several layers to more than 10 layers. Interstitial lamellae: They are irregular lamellae which occupy the intervals between the Harversian system. Circumferential lamellae: At the external surface of the bone, there are the outer circumferential lamellae. These consist of several lamellae that run about the circumference of the shaft of bone. A similar but less well developed system of lamellae is present on the inner surface of the bone, the inner circumferential lamellae. There are a lot of black ovoid lacunae between the lamellae where the osteocytes are placed. Many delicate channels radiated from the lacunae are canaliculi where the cytoplasmic processes of the osteocytes project into. The canaliculi in the adjacent lamellae are connecting with each other. Slide 60 Compact Bone ( Ground Bone ) Dialia Violet This section was prepared by cutting thin slices in longitudinal section with a saw and grinding these down to the required thickness with abrasives. Slide 12 Decalcified Bone ( Compact Bone ) H.E. In order to obtain sections thin enough for studying the 11 BONE organic constituents of bone, the tissue has to be “decalcified” by seaking it for a long period in a dilute acid solution which dissolve the bone salts. A bone treated in this manner retains its riginal appearance and microscopic structure but is soft, flexible and can be easily cut with a microtome knife after embedding in wax. This is a transverse section of bone. The bone tissue appears red, because the matrix of the decalcified bone has high content of collagen. Within the Harversian cannel, the vessels connective tissue and nucleus of the osteocytes within the lacunae can be seen. Slide 59 Decalcified Bone ( Compact Bone ) This is a longitudinal section of decalcified bone. 12 H.E. DEVELOPMENT AND GROWTH OF BONE DEVELOPMENT AND GROWTH OF BONE Objective: To understand the development of bone. Slide 54 Endochondrial Ossification ( Finger ) H.E. There are 2 or 3 phalangs inside the finger, the 2 blue large ends of the phalange are epiphysis and the pinkish intermediate portion is diaphysis of long bone. Select a typical phalange and study from epiphysis to diaphysis. Recognize the 4 zones starting from the articulate cartilage. Resting zone: It consists of hyaline cartilage, the chondrocytes are small without morphologic difference from the ordinary hyaline cartilage. Proliferative zone: Chondrocytes divide rapidly and form paralleled raws of flattened cells along the long axis of bone. Toward the diaphysis the chondrocytes become hypertrophy. Calcified cartilage zone: It contains large chondrocytes, some of them are vacuolated and the diminished matrix is calcified that is stained in deep-blue. Ossification zone: The chondrocytes undergo degeneration 13 DEVELOPMENT AND GROWTH OF BONE and the thin partitions of matrix between the lacunae with a raw are dissolution.The blood capillaries and undifferentiated cells origination from the periosteum invade the cavity left by the chondrocytes. These gaps are primitive marrow cavity. Farther towards the center of diaphysis the residual calcified cartilage matrix is stained in pink or substituted by osseous matrix completely. These are newly-formed osseous trabeculae. The marrow cavity: The trabeculae are resorbed that the primary marrow cavities are joined with each other forming a large cavity which lies in the central of the diaphysis with red marrow and blood sinuses in it. The sequential processes of endochondrial ossification may be summarized as: cartilage model formation → cartilage proliferation → cartilage regression → cartilage destruction →bone formation. Observe the ossification zone in detail. There are osteocytes embedded in the trabeculae. Pay special attention to the morphological features of the osteoblasts and osteoclasts. Osteoblasts: These cells frequently lie in single row on the surface of new bone. They are cuboidal or irregular in shape with basophilic bluish-purple stained cytoplasm and large round eccentrically placed nuclei. The osteoblasts secret osseous matrix. As soon as they are embedded in the matrix, they are no longer osteoblasts but osteocyts. Osteoclasts: They are large, irregular, multinucleated cells 14 DEVELOPMENT AND GROWTH OF BONE which usually present an acidophilic cytoplasm lying within the depressions in the bone where the bone is being resorbed. Slide 55 Intramembranous Ossification ( Skull of Embryo ) H.E. This is a section through the center of ossification in the skull. Move the slide and locate the parietal area, you will be able to see bone deposition within mesenchyme as a result of the transformation of mesenchymal cells into osteoblasts. Some of the osteoblasts have already been entrapped in the bone as osteocytes, the others still left on the surface of bone trabecula. Sometimes osteoblasts can be seen. 15 BLOOD BLOOD Objective: To grasp the functions and morphological feature of erythrocytes, neutrophils, eosinophils, lymphocytes, monocytes. To understand the function and morphology of basophils, platelets. Preparation and Staining of Blood Smear (1) Method of Obtaining blood Blood may be obtained from the free margin in lobe of an ear or finger top. Because they are less sensitive to be punctured. (2) Preparation of the Blood Smear Take a small drop of blood on a chemically clean and dust-free slide about 2 cm from the end, taking care that the slide does not touch the skin. Place the slide on a table or flat surface. With the thumb and forefinger of the right hand hold the end of a second slide against the surface of the first at an angle of 30 to 40 degrees. The drop will immediately run across the end, filling the angle between the two slides. If the drop of blood was of appropriate 16 BLOOD size, the thin portion of the film is about 3 cm. The film should be allowed to dry in the air. (3) Blood Stains Wright’s stains are compounds of eosin Y with methylene blue altered by the action of alkalies so as to contain a variable amount of azure B, azure A, and methylene violet. Method 1. Lay thin smear face up on a horizontal staining rack. 2. Cover smear with Wright’s staining solution (about 15 drops). 3. Let sit for 1 minute and then add twice the volumn of distilled water. You should see a metallic sheen on the solution before proceeding with step 4. Allow the water and dye mixture to remain on the slide at least 2 minutes. 4. Drain off and rinse with water until the thinner portions of the blood film are pink. 5. Blot dry, and mount in synthetic mounting medium. Slide 24 Blood Smear Wright’s Stain Select an area in which the cells are evenly distributed. The fields you view consist of a preponderance of erythrocytes interspersed with blood platelets and nucleated leucocytes. Remember that there are 500 or more red blood cells to one white cells. You may need to look around the slide for some while before 17 BLOOD typical and unmistakable example of the various white cells are found. The higher power objective will usually be necessary: Set your microscope up to give maximum brightness without glare. Wrong condenser setting will give false impressions of the colour of intracellular granules. Erythrocytes -- red blood corpuscles. They are most numerous, they are anuclear, biconcave disk. Owing to their richness in hemoglobin, a basic protein, erythr ocyte are red-staining. Leucocytes -- white blood corpuscles. These appear scattered randomly in a blood film, identifiable by their basophilic nuclei. In normal blood there are 5 types of leucocytes of two categories: Neutrophils: They are the most numerous of white blood cells. These comprise 60-70% of the white blood cells. Their cytoplasm is slightly acidophilic with fine, pale pink neutrophilic granules. The nucleus is divided into 2-5 lobes (usually 3 lobes) linked to each other by chromatin strands. Eosinophils: They are characterized by an abundance of coarse, uniform size red granules (acidophilic granules). The nucleus often consists of two lobes connected by a strand of 18 BLOOD chromatin. Basophils: They constitute about 0.5-1% of the total number of leukocytes and are, therefore, difficult to find. The cytoplasm contains numerous basophilic deep-blue granules which are different in size. The pale-stained nucleus is irregular in shape and always obscured by overlying granules. Lymphocytes: Their number in normal adults varies from 20-30% of the total white blood cell count. The small lymphocyte is the most commonly seen in blood smears, but medium-sized lymphcytes and lymphocyte as large as 18 um in diameter are occasionally present. The small lymphocyte has a round, often with a slight indentation, deep-purple nucleus which is enclosed by thin rim of sky-blue-stained cytoplasm. The large lymphocyte has more cytoplasm which may contain a few coarse azurophilic granules. Monocytes: They are the largest leukocytes, the nucleus is irregular, kidney or horse-shoe in shape, the chromatin apppears in a looser arrangement than in the lymphocytes. Platelets -- They are irregular fragments of cytoplasm with fine purple granules, they appear in small clusters among the blood cells. 19 HEMATOPOIESIS HEMATOPOIESIS Objective: To understand the morphology and structures of developing blood cells in red bone marrow. Slide 53 Bone Marrow Smear Wright’s Stain Before you begin this exercise, review the morphology and nomenolature of the developing blood cells of both myeloid and erythoid series. Select an area in which the cells are evenly distributed. Many cells are damaged in preparing the smears and will cause some confusion. If in doubt, ask the instructor to verify that you are studying a good example of the cell in question. 1. Myeloid Series: Myeloblast: The most undifferentiated cell which can be recognized is a large cell with basophilic cytoplasm, no granules and a large round nucleus with lacy chromatin and prominent nucleoli which appear as lightly staining spheres within the nucleus. Promyelocyte: Azurophilic granules begin to appear in the 20 HEMATOPOIESIS cytoplasm. The cytoplasm is less basophillic and the nucleus is still round or oval. Mucleoli may still be seen in the nucleus. Neutrophilic myelocyte: The cell contains both azurophilie granules and neutrophilic granules. Neutrophilic granules are very small, yellow to pink in color, and are not easily resolve in the light microscope, but clusters of these granules give the cytoplasm a pink to yellow cast. The nucleus of noutrophilic myelocyte is typically ovoid or slightly indented and the chromatin is more condensed. Neutrophilic metamyelocyte: The nuclear indentation becomes prominent and the nucleus becomes orectic. Mature or polymorphonuclear neutrophils 2. Erythrioid series: Erythroid cells are less abundant than myeloid elements, since the ratio of myeloid to erythroid cells (M:E ratio) for normal marrow is about 3:1 . Cells of the erythroid series never possess cytoplasmic granules. Erythroblasts with obviously basophilic (blue stained) cytoplasm and increasingly smaller cells with purplish stained cytoplasm and increasingly small and densely stained nuclei. The changes in the cytoplasm are caused by the increasimg amount of haemoglobin present which produces a gradual change of sraining from blue ( basophilic erythroblast ) to purple or gray 21 HEMATOPOIESIS AND MUSCLE TISSUE (polychromatophilic erythroblast) and finally to pink (late erythroblalst). The nucleus become dense and pyknotic and is eventually ejected from the cell when the mature red cell is formed. The late erythroblalst is allso sometime termed “normoblast” in order to distinguish it from the abnormally large erythroblast “ megaloblast ” which is present in the marrow of patient suffering from vitaminB12 deficiency (pernicious anaemia). 3. Notice the large megakaryocytes with multilobular nuclei. Slide 61 Bone Marrow Section ( Rib ) H.E. In this slide identify the large megakaryocytes with multilobular nuclei. Notice the presence of many fat cells. 22 MUSCLE TISSUE MUSCLE TISSUE Objectives: To grasp the morphological features of skeletal muscle , understand the morphological features of cardiac muscle, smooth muscle. Slide 14 Skeletal Muscle ( Longitudinal Section ) H.E. The skeletal muscle is composed of long cylindrical multinucleate cells — the muscle fibres. Each fibre has an extensible sheath — the sarcolemma. A number of oval nuclei are usually immediately under the sarcolemma. The pink sarcoplasm contains large number of myofibrils.Locate an area that shows the bandings, and identify the dark A bands interspersed with pale I bands. Identify the delicate, dark Z-line which transverses the I band. The portion of a myofibril between two Z-lines is called a sacomere. In relaxed muscle fibres you may be able to detect a somewhat paler H zone in the center of each A band. 23 MUSCLE TISSUE Slide 14 Skeletal Muscle ( Cross Section ) H.E. The muscle fibres may be angular in cross section. The nuclei are located at the periphery of the muscle fibres. With high power objective, it may be seen each fibre subdivided everywhere into small angular fields—Cohnheim’s area, which are themselves finely dotted. The dots represent sections of the myofibrils of which the fibres are composed. Between the fibres is a certain amount of connective tissue, which serves to support the blood-vessels and to unite the fibres into fascicule;known as the endomysium. A group of muscle fibres are surrounded by small amount of connective tissue perimysium. A number of bundles are aggregated into a muscle and united with connective tissue epimysium. Slide 13 Skeletal Muscle Iron hematoxylin High magnification of muscle fibers demonstrates the cross-striations. The A bands are prominent, dark-staining bands; a lighter middle region, the H bands, is not visible. The I bands are equally prominent and are lightly stained bands. Crossing each central portion of the I bands are distinct, narrow lines, the Z lines. Slide 23 Cardiac Muscle ( Heart ) 24 H.E. MUSCLE TISSUE In longitudinal section, the cardiac muscle fibres differ from those of skeletal fibres in the following particularis. (1) The fibres are clearly branched, and united by their branches. (2) Their nuclei often lie near center of the fibres and oval in shape. (3) The cross striations (with A band, I band, M line and Z line) are identical to those of skeletal muscle, but their striations are less marked. (4) The fibres are interrupted by thin transverse lines—the intercalated discs which look like lightly dark-stained short lines. Between the fibres is a certain amount of connective tissue which serves to support the large amount of capillaries. In cross section, the cardiac muscle fibres are round in shape with numerous finely dotted in cytoplasm. The dots represent sections of the myofibrils of which the fibres are composed, sometimes they are disposed radially. Large, ovoid nuclei, usually one per cell, occupy the central position. Slide 3 Smooth Muscle (Stomach) H.E. The smooth muscle is mainly visceral in distribution . In the stomach, the muscularis is formed by several layers of smooth muscle fiber. Smooth muscle cells are stained deeper than the 25 MUSCLE TISSUE connective tissue, arranged in layers of different direction and so cut in both longitudinal and cross sections. In longitudinal section, the muscle cells are elongated fusiform-shaped. The nucleus is rod-shaped, centrally located with fine chromatin, commonly one or two nucleoli. The nucleus is shortened or thrown into folds when the muscle cell contracts. The cytoplasm of muscle cells is called sarcoplasm. Although myofibrils are present in the cytoplasm they cannot be seen at the light microscope level. Between smooth muscle fibres are capillaries and fibroblasts. Compare the differences between the nuclei of fibroblasts and smooth muscle cells. Examine the outer longitudinal layer of muscularis external in the same slide, where the muscle is cut transversely. In cross-section, the smooth fibers are usually round or angular. Since smooth muscle cells are elongated cross sections cut through them seldom pass through their nuclei. The nuclei are found in largest profiles, which represent sections through the central portions of the fibers. 26 NERVE TISSUE NERVE TISSUE Objectives: To grasp the morphological features of neuron; To grasp the morphological features of nerve fiber; To understand the neuroglial cell; To understand the morphological features of nerve ending (tactile corpuscle, lamellar corpuscle, end plate). Neuron Slide 15 Motor Neuron ( Spinal Cord ) H.E. The large cells, scattered through the H-shaped gray matter are nerve cells. Examine the motor nerve cells in the ventral horn (ventral horn are short and thick).The cell is polyhedral or irregular in shape with some short processes. The cytoplasm is filled with finely granular or clumps of basophilic material called Nissl’s bodies. The nucleus is typically large spherical and centrally located with finely dispersed chromatin(vesicular nucleus). The 27 NERVE TISSUE nucleolus is prominent, large, dense, and stains dark. Sometime you can find the axon hillock, which contains no Nissl material, marks the site of origin of the axon. On the other hand, the neuroglial nuclei are only stained prominently, whereas their cytoplasm remains unstained. Slide 16 Motor Neuron ( Spinal Cord ) Nissl stain The section is similar to the slide 15 in shape, but stain method is not the same. Examine the motor nerve cells in the ventral horn (ventral horn are short and thick).The cell is polyhedral or irregular in shape with some short processes. The cytoplasm is filled with Nissl’s bodies which are stained as blue colour. The nucleus is large spherical and centrally located with a large, prominent nucleolus. Nerve Fibers Slide 17 Myelinated Fibers ( Sciatic Nerve ) H.E. Cerebropspinal nerves are composed chiefly of myelinate fibres. The slender strip is longitudinal section of sciatic nerve and the small round one is a cross section. First you examine the longitudinal section.The nerve fibres are gathered up into round bundles and these are again united to form the nerves. 28 NERVE TISSUE A nerve fibre is made up of a central axis cylinder (a process of a neuron), a sheath of myelin, a neurolemma or Schwann sheath and a delicate connective tissue sheath—the endoneurium. The nerve fibre is interrupted at regular intervals, at these places the neurolemma appears to produce constrictions which are called nodes of Ranvier. A reticular appearance has been noticed in the myelin sheath after fixation with alcohol, the neurokeratin network, but it varies greatly in aspect and is certainly produced by the action of the reagents employed to show it. Schwann cells constitute the sheath of Schwann or neurolemma sheath. The pale oval nuclei of the Schwann cells can sometimes be seen. In the cross section of sciatic nerve, we can see the nerve fibres are gathered up into round bundles. The connective tissue connected the bundles and invested the whole nerve is called epineurium. That which sheathes the bundles is known as the perineurium. The delicate connective tissue which lies between the nerve fibres of the bundle is termed endoneurium. Slide 18 Myelinated Fibers ( Sciatic Nerve ) Osmic Acid Stain Examine this slide. Osmic Acid stains the lipid in the myelin sheath black. So the myelin sheath appears as a thick, black band surrounding a lighter, central axon. Node of Ranvier can be seen where the myelin sheath exhibits discontinuity. 29 NERVE TISSUE Slide 73 Unmyelinated Fibers ( Sympathetic Nerve ) H.E. The non-myelinated fibers devoid of the distinct double contour which is characteristic of the absence of a myelin sheath. They are beset with numerous nuclei which have ususally been regarded as belonging to a delicate sheath, although it must be admitted that the nuclei often appear to lie in the substance of the fibres rather than at their surface. Neuroglia Slide 15 Neuroglia ( Spinal Cord ) H.E. With H.E. stain, neuroglia only the nuclei and a little of the adjacent cytoplasm can be seen. Astrocytes: Their nuclei are large, round and lightly stained. Microglia cells: Their nuclei are small oval, rod-like or irregular in shape and deeply stained. Oligodendroglia cells: Their nuclei size are intermediate between the astrocytes and microglia cells, they are round shape. Ependymal Cells: They line the central canal of the spinal cord. They are a layer of simple columnar ciliated epithelium cells. Nerve Endings Slide 19 Tactile Corpuscles ( Skin of Finger Tip ) H.E. Tactile corpuscles (Messner’s Corpuscles) occur in some of 30 NERVE TISSUE the dermal papillae of the skin. Tactile corpuscles are ovoid in shape. The flattened cells of capsule are arranged in the form of multiple-stacked lamellae. Unmyelinated nerve terminals enter the corpuscle, where they branch and follow a spiral course among the connective tissue. Slide 19 Lamellar Corpuscles ( Skin of Finger Tip ) H.E. Lamellar corpuscles ( Pacinian Corpuscles) are large and have a more complex structure. They are located deep in the dermis and subcutaneous tissue. They are composed of a number of concentric lamellae resemble a sliced onion in the section. Between the lamellae is a small amount of loose connective tissue with flat fibroblasts. A thin, dense connective tissue encloses the lamellar corpuscles. Slide 20 Motor End Plate ( Intercostal Muscle ) AuCl This slide is a small piece of gold impregnated muscle press slide. Muscle fibres are purple in colour, myelinated fibres are stained as black colour. A myelinated fibre will branch two or three times before ending, and then each branch passes directly about the middle of a muscle fibre.The axis-cylinder ends in a close terminal ramification with various expansions upon its branches. 31 NERVOUS SYSTEM NERVOUS SYSTEM Objectives: To grasp the structures of the cerebral cortex; To grasp the structures of the cerebellar cortex. Cerebrum Slide 56 Cerebrum H.E. This is a part of cerebrum. Overlying and covering the surface of cerebrum is the delicate connective tissue of brain, the pia mater containing many small vesseles. Beneath the pia mater cerebral cortex is present. Although there are variations in arrangement of cells in different parts of the cerebral cortex, six distinct layers are recognized from outside to inside. Molecular layer is located in the outermost layer. Blood vesseles are found. External granular layer is rich in granule cells. External layer of pyramidal cells is thicker than the external granular layer. It is composed of the medium-sized pyramidal cells. Internal granular layer contains numerous stellate cells. 32 NERVOUS SYSTEM Internal layer of pyramidal cells is mainly composed of larger pyramidal cells. Multiform layer is near to the white matter of brain. There are fusiform cells, granule cells, stellate cells. All of these cells vary in size. Slide 71 Pyramidal Cell ( Cerebral Cortex ) Golgi’s Method This is a thick celloidin section of Golgi Silver preparation of dog brain. This method shows the complete contour of nerve cells in the cortex. The bodies of pyramidal cells are triangular in shape and various in size. The typical large vesicular nucleous with its prominent nucleolus is outlined. The most prominent cell process is the apical dendrite, which is directed toward the surface of the cortex. Several dendritic collaterals are given off along its course through the cortex. Smaller dendrites arise from other parts of the cell body. The axon arises from the base of the cell body and passes into the white matter. The intercellular area is occupied by nerve fibers of various cells in the cortex, small astrocytes, and blood vessels. Each pyramidal cell has several basal and one large apical dendron. Each cell has a single slender axon, which is usually directed towards the medullary center. 33 NERVOUS SYSTEM Cerebellum Slide 57 Cerebellum H.E. The section of cerebellum appears leave-like in shape. The out cortex of cerebellum is gray matter, the inner is the white matter which consists of myelinated nerve fibers or axons.The grey matter can be distinguished into three cell layers from outside to inside. Molecular layer is thicker than other layers, near to the superficial layer of the grey matter with few cells. Purkinje cell layer is a thin layer with Purkinje cells, which are large and pyriform in shape with ramified dendrites that extend into the molecular layer. Granular layer contains numerous small cells with intensely stained nuclei. Slide 72 Purkinje’s Cells (Cerebellum Cortex ) Golgi’s Method The slide is also a thick celloidin section. In the cortex Purkinje’s cell is a large flask-shaped cell. Each of these cells gives off from its base a fine process, the axon, while from the opposite pole of the cell large remified processes ( dendrites ) extend into the superficial layer of the grey matter.The dendrites spread out in planes transverse to the direction of the lamellae. 34 NERVOUS SYSTEM Ganglion Slide 1 Spinal Ganglion H.E. Examine the slide of spinal ganglion with a capsule. The neurons are pseudounipolar, the processes are unsectioned. The cell body can be spherical, ovoid, or angular, they are very large and arranged in groups separated by bundles of nerve fibers. With the 40x objective, the nucleus is large spherical and centrally located, with finely dispersed chromatin (vesicular nucleus). The nucleolus is large and well developed. These neurons usually show fine Nissl’s bodies and droplets with fuchsin. Each nerve cell is surrounded by a layer of flat satellite cells.Their nucleus is darker. Slide 73 Sympathetic Ganglion H.E. Similar to the spinal ganglion cells. In contrast to spinal ganglion cells, the cells are multipolar neurons and are smaller and more uniform in size. As a result, the outlines and their processes of the sympathetic ganglion cells appear often irregular in the sections. Their nuclei are often eccentric and binucleated cells are not uncommon. Most of these cells contain lipofuscin pigment in their cytoplasm. Satellite cells are usually less numerous than around the cells in spinal ganglion. The capsule may not be well defined, more unmyelinated nerve fibers are pressent in the intercellular area. 35 CIRCULATORY SYSTEM CIRCULATORY SYSTEM Objectives: To grasp the morphological features of three type capilaries; To grasp the morphological features of medium-sized artery, large artery, small artery, and heart wall; To understand the morphological features of medium-sized vein, large vein , small vein. Slide 21 Medium-Sized Artery H.E. This is a section through both femoral artery, vein and nerves. Locate the femoral artery which has a thick muscular wall—muscular artery. An artery is composed of three coats: Tunica intima is lined by a thin layer of endothelium, the cells of which are somewhat elongated in the direction of the axis of the vessel, and form a smooth lining to the tube. Next to the endothelium of the arteries is a subendothelial layer of connective tissue, which is not distinct. However, a prominent , wavy internal elastic membrane ( elastica interna ) is well 36 CIRCULATORY SYSTEM developed. The tunica intima appears sealloped because of postmortem contraction of smooth muscle in the tunica media. Tunica media is a thick layer, and consists mainly of circularly arranged smooth muscle fibres. They have long rod-shaped nuclei. The muscle cells are often very irregular. Between muscle cells are fine collagenous fibres and elastic fibres. Tunica adventitia is conposed of external elastic membrane, (elastica externa) which is split into several lamellae, and a layer of loose connective tissue, consisting mainly of collagenous fibres, and elastic fibres. Nevers are also present. Slide 21 Medium-Sized Vein H.E. It has a relatively thinner wall and a larger lumen than the accompanying medium-sized artery. The veins resemble the arteries in general structure, but exhibit certain differences. In the tunica intima the same layers are present, but the elastic tissue is less developed, and may be quite inconspicuous; it seldom take the form of a completed membrane. The tunica media contains less elastic tissue and also much less muscular tissue, being partly occupied by connective tissue fibres. The tunica adventitia is relatively well developed. It is about twice as thick as the tunica media. 37 CIRCULATORY SYSTEM Slide 3 Small Artery and Small Vein ( Stomach ) H.E. In the stomach wall, there are small blood vessels. The structure of small artery is similar to that of the larger ones, but the tunica media is much thicker, and the collagenous fibres of tunica adventitia merge with the surrounding tissue. The small vein are frequently accompanied closely with small artery. The small veins are much thinner-wall vessels. They have a high proportion of lumen to total diameter. The tunica consists of flattened endothelium and sparse connective tissue elements. The veins are usually filled with blood. In fact, they also can be seen in the adventitia of the muscular artery or vein. Slide 22 Large Artery ( Aorta ) H.E. This is an example of elestic artery. Similar to the wall of other vessels. Three layers can be identified. Tunica intima is lined by the usual endothelium; outside this is a considerable thickness of subendothelial connective tissue, with elastic tissue chiefly composed of fine fibres, it is not especially marked off by a definite elastie layer from the tunica media. Tunica media: There is a great development of elastic tissue in this tunica, where is forms membranous layers or lamellar networks which alternate with the muscular layers. A good deal of connective tissue also takes part in the formation of this layer. 38 CIRCULATORY SYSTEM This tunia consititutes almost the entire thickness of the wall, the tunica intima and tunica adventitia being thin. Tunica adventitia: This layer is composed mainly of collagenous fibres, and some elastic fibres extending out from the outermost layer of elastic membrane. Also present in the tunica adventitia are small blood vessels and small bundles of nerve fibres. Slide 23 Capillaries ( Heart ) H.E. In the connective tissue between the cardiac muscle, there are numerous capillaries. They are very small, and have an average diameter of 7 to 9 um. The capillary is made up of one or two endothelial cells in section. The nuclei of the endothelial cells are usually bulging into the lumen of the capillary. Slide 23 Heart H.E. The wall of the heart consists of three layers: The middle myocardium, an outer epicardium and an inner endocardium. The innermost layer of the heart wall is endocardium. The outline is much less regular than the outer surface. The inner surface is lined by a single layer of endothelial cells. Immediately beneath the endothelial cells is the thin subendothelial layer, containing mainly fibroblasts and fine collagenous fibres. External to this is a thick layer of connective tissue, called 39 CIRCULATORY SYSTEM subendocardial layer. It contains collagenous, elastic fibres and also some isolated bundles of smooth muscle cells. In addition, this consists of branches of specialized impulse conducting cardiac muscle — Purkinje fibre. The myocardium forms the main thickness of the heart. It is composed of a network of cardiac muscle fibres. The muscle fibres are bound by connective tissue which consists of network of reticular and collagenous fibres. In the connective tissue run numrous capillaries and various sizes blood vessels. The myocardium is covered externally by a layer of serous membrane — the epicardium. It is composed of a single layer of mesothelial cell and a thin layer of loose connective tissue containing both elastic and collagenous fibres. Fibroblasts, fat cells and blood vessels are also present in the epicardium. Slide 23 Impulse Conducting System ( Sheep Heart ) H.E. The Purkinje fibres have a widespread distribution in the endocardium. Their diameter is much larger than fibres in the myocardium. The myofibrils are sparse, and peripherally displaced. The sarcplasm stains paler due to the paucity of myofibrils. The nuclei of the fibres are centrally located, and are surrounded by an unusually large amount of sarcoplasm. 40 IMMUNE SYSTEM IMMUNE SYSTEM Objectives: To grasp the morphological features of lymph nodes, spleen; To understand the structures of the thymus. Slide 8 Lymph Node H.E. Lymph node is an ovoid or kidney-shaped organ. It is composed of two main parts: peripheral deeply stained cortex and central palely stained medulla. Lymph node is a discrete body surrounded by a capsule of connective tissue, from which the connective tissue extends into interior to form trabeculae. At the hilum, the capsule is thickened and extends deeply into the node, in which many blood vessels extend and 1-2 efferent lymthatic vessels with wider lumen can be found. The afferent lymphatic vessels is located in the capsule. They possess valves which open toward the node while the efferent lymphatics have valves which open outward from the node. The fine reticular fibres which form both the capsule and the trabeculae to constitute the reticular framework of this organ. 41 IMMUNE SYSTEM In cortex the main structures are: lymph nodules: They are composed of large number of densely aggregated lymphocytes. The central portion of the each nodule is stained pale and is called germinal center, which is mainly composed of B lymphocytes. A typical nodule with a cap, a dark and light zone can be seen at times. The peripheral part of nodule consists of closely aggregated small lymphocytes with deeply stained round nuclei. It also contains reticular cells and macrophages, the former contain pale staining nuclei and boundaries of the cell are unclear, the latter are large in size and their cytoplasm are stained in red. Paracortical region is that portion of the diffuse lymphoid tissue located in the deep region of the cortex and between the adjacent lymph nodules. In paracortical region T lymphocytes are located. Post capllary venules are situated in the paracortical zona near the medulla, lined by a layer of 4-6 cuboidal endothelial cells. Lymph sinuses: Nodules are separated from the capsule and trabeculae by channel like spaces—lymph sinuses, which are divided into subcapsular and peritrabecular sinuses. In medulla it consists of medullary cords and medullary sinus. Medullary cords are deeply stained strands of densely aggregated lymphoid tissue which branch and connect each other. 42 IMMUNE SYSTEM It is also composed of aggregated lymphocytes, reticular cells and macrophages. Medullary sinus: The relatively cell-free areas between the medullary cords are medullary sinuses, bridged by reticular fibre supporting endothelial cells. Medullary sinus contains several types of cells of reticular tissue: reticular cells, macrophages and lymphocytes. Reticular cells are stellate in shape with several processes, pink cytoplasm, centrally placed pale round or ovoid nucleus and prominent nucleolus. Marophages are round or irregular in shape with deeply stained cytoplasm contain engulfed granular particles or cell debris. Lymphocytes are mostly small lymphocytes. They are round in shape with scanty cytoplasm and large round nuclei. Slide 25 Spleen H.E. The spleen consists of three parts— white pulp, red pulp and marginal zone. The capsule encloses the surface of spleen and is relatively thick. It consists of dense connective tissue containing a few smooth muscle cells in addition to fibrous elements and has smooth outer surface covered by peritoneal mesothelium. It extends into parenchyma and forms trabeculae,which froms a three dimensional supporting network and carries inwards blood 43 IMMUNE SYSTEM vessels, lymphatics and nerves from the hilus. Between them reticular fibers form both coarse and fine networks upon which various cells are supported. White pulp scatters throughout the spleen and is deeply blue stained round or ellipsoid bodies. White pulp is composed of splenic nodules and periarterial lymphatic sheath. Splenic nodules as lymphatic nodules are a corpuscle of dense lymphoid tissue containing sometimes a germinal center and central artery. Unlike the nodules in other situations they form sheathes around small arteries Periarterial lymphatic sheat is tube-like structure made of dense lymphatic tissue cords around the central artery. Red pulp contains splenic cords and sinusoid. Splenic cords lie around the sinusoid and are composed of lymphoid tissue with numerous blood cells. Sinusoids are the large irregular lumens containing RBC. Its endothelial cells are larger than that of blood vessels and bulge into lumen with their round of rod nuclei. As the arteries which course through the white pulp, they enter the red pulp and give rise to groups of small branches called penicili. They may be recognised, at the periphery of some areas of the white pulp, as small irregular bundles of arterioles in connective tissue. In the red pulp these again branch to form small vessels called ellipsoids or sheathed arteries. The ellipsoids are 44 IMMUNE SYSTEM either directly continuous with the venous sinusoids or may open into the spaces of the red pulp, from there the blood will return to vascular system through the walls of the venous sinusoid. The veins into which the blood drains are found close to or surrounded by trabecular tissue. Slide 65 Thymus H.E. Thymus is surrounded by a thin connective tissue capsule, from which trabeculae extend into parenchyma and separate it into numerous incomplets lobules of various size and shape. The periphery of each lobule stains deeply and is called cortex, while the central portion stains pale, called medulla. Since the lobules are incomplete, the medullae are continuous between adjacent lobules. Cortex is mainly composed of large number of closely aggregated lymphocytes. There are numerous capillaries among them. Medulla is essentially the same in structure as that of cortex but lymphocytes are not so densely aggregated. In the central region of medulla, there also are a number of red-stained thymic corpuscles. The thymic corpuscle is small round corpuscles of various size, each lobule contains one or more in number. It is composed of flattened epithelial reticular cells arranged concentrically, these cells become degenerated with shrank nuclei. 45 IMMUNE SYSTEM The cells of the corpuscle center are completely degenerated becoming the red homogenous structure. Slide Palatine Tonsil H.E. The deeply stained side of this section is epithelium which invaginates in some areas to form crypts. The deep blue portion underlying the epithelium is lymphoid tissue, out of which is the pink stained capsule. The epithelium of tonsil is nonkeratinized stratified squamous epithelium, which may infold in some places to form crypts. It may be infiltrated with small lymphocytes and if the infiltration were severe, the epithelium would decrease in layer or even lose its normal pattern leaving only surviving epithelial cells or their nuclei. Lymphatic tissue distributes in the lamina propria beneath the epithelium and around the crypts. It forms many lymphatic nodules arranged in rows and surrounded by diffuse lymphatic tissue. Several isolated masses of epithelium and lymphatic tissue would appear. Capsule is made up of loose connective tissue outside the lymphatic tissue. Sometimes connective tissue extends into the tonsil to form trabeculae. A few mucous glands may be seen in exterior of the capsule. 46 DIGESTIVE TRACT DIGESTIVE TRACT Objectives: To grasp the morphological features of esophagus, stomach, small intestine(duodeum, jejunum, ileum, and large intestine). To understand the structures of the tongue. Slide 62 Tongue ( Filiform Papillae ) H.E. The purple-stained parts is epithelium, under which the pink coloured narrow zone is lamina propria. The deeply red stained lower thick parts is the zone of skeletal muscle. Filiform papillae are elongated conical in shape and quite numerous, and are present over the entire surface of the tongue. The surperficial cells of the epithelium are frequently partially keratinized with red staining cytoplasm and wrinkled nucleus. The underling connective tissue projects toward the epithelium forming primary papillae which again project deeply to the epithelium forming secondary papillae. 47 DIGESTIVE TRACT Slide 62 Tongue ( Fungiform Papillae ) H.E. They have a mushroom-like outline and are less numerous than the filiform papillae. The epithelium is thinner and nonkeratinized. The connective tissue core bears several secondary papillae. Within the epithelium, taste buds can be found. Slide 62 Tongue ( Circumvallate Papillae ) H.E. This is a transverse section through the posterior 1/3 of the tongue. Identify the circumvallate papillae in this section. The circumvallate papillae are larger papillae with expanded and flattened top, and surrounded by a deep grove. There are many taste buds stained pale in the epithelium of their lateral wall. Taste buds: The taste buds are seen as pale, oval bodies embedded in the darker-stained epithelium. The cells of tast bud are long spindle-shaped. Two types of cells can be distinguished: The taste cells are stained deeper and on their free surface are taste hairs which project into the taste pore. The supporting cells are stained pale and have a large round or ovoid nucleus. Slide 4 Esophagus H.E. Master the four principal layers of digestive tract and observe 48 DIGESTIVE TRACT the characteristics of each layer carefully. The outline of the lumen is irregular in this transverse section. There are many longitudinal folds projecting into the lumen. Mucosa: Immediately surrounding the lumen is a thick, stratified squamous epithelium. Lamina propria is composed of loose connective tissue which protrudes to the epithelium and forms papillae. Muscularis mucosa is a thin layer of longitudinal smooth muscle. Submucosa: It is composed of loose connective tissue with plenty small blood vessels and the esophageal glands. Muscle layer: Basically, the inner layer muscularis is circular and the outer longitudianl, but the arrangement of muscle is less regular. It will contains skeletal muscle if the section is taken from upper half of the esophague. Advantitia: It consists of loose connective tissue containing blood vessels and nerves. Slide 3 Gastric Fundus ( Stomach ) H.E. The weavy bluish-purple stained side is mucosa and the remainder pink portion contains the rest coats. The surface of mucosa is lined by a simple columnar mucous secreting cells. At intervals the epithelium dips downward forming the gastric pits, under the epithelium is the 49 DIGESTIVE TRACT lamina propria which contains the straight tubular glands (or gastric glands) open into the base of the gastric pits. The glands may be present as longitudinal, oblique or cross section, three types of cells can be identified: Chief or zymogen cells are located in the middle and lower portion of glands. They are pyramidal in shape with deeply stained basophilic cytoplasm and basally located round nuclei. In some cases, fine secretory granules may be seen in the apical region of chief cells.. Parietal cells are present mainly in the neck and the body of the glands. The cells are easily recognized by their triangular shape and acidophilic cytoplasm. The nucleus is round and situated in the center of the cell. Double nuclei may be seen in these cells. Mucous neck cells are present mainly in the neck region interspersed with parietal cells. The cells are columnar-shaped. The apical cytoplasm is full of mucus that makes the cells staining faintly. The nucleus is oblate in form and is squeezed to the base of the cell. (Argentaffin cells occur in the deepest parts of the gland, but are not usually recognized). Underneath the base of the glands, find the muscularis mucosa, usually it consists of an inner circular, outer longitudinal muscle layers. The submucosa consists of connective tissue, in which larger 50 DIGESTIVE TRACT blood vessels and lymph vessels are located. The muscularis is rather thick and consists of three layers: outer longitudinal middle circulalr, and inner oblique. The serosa is composed of a thin layer of loose connective tissue and mesothelial lining. Slide 27 Esophagus-Stomach Junction H.E. A section through the junction of esophagus and the stomach. Note the epithelial transition at the junction. Slide 28 Pylorus-Duodenal Junction H.E. A section through through the junction of pylorus and duodenum. Note epithelial transition. In pylorus the gastric pits are deeper than that fundus. Pyloric glands columnar with striated border. The goblet cells are interspersed. Slide 29 Duodenum ( Small Intestine ) H.E. Identify the four layers of the wall of the small intestine under low power, then concentrate on the mucosa. Mucosa: The villi with which the whole of the inner surface of the small intestine is closely beset are projections of the mucous membrane and are composed of connective tissue covered with simple columnar epithelium. Between and at the 51 DIGESTIVE TRACT base of the epithelial cells many leucocytes occur. Further, oval spaces at intervals represent the positions of goblet cells with their content (mucigen), dissolved during preparation. The remaining cells are absorptive cells. Each villus has a central connective tissue core, the lamina propria. In the middle of the villus is a lymphatic vessel, known as the central lacteal. Surrounding the lacteal are fine bundles of longitudinal smooth muscle fibres. Note that the free surface of the absorptive cell is specialized to form a definite striated border. The mucous membrane proper is provided with simple tubular glands—the crypts of Lieberkuhn(intestinal glands) which are lined throughout by columnar epithelium; with scattered goblet cells. At the fundus of each crypt are a few cells containing well-marked oxyphil granules known as the Paneth cells. Muscularis mucosa: The mucosa is bounded next to the submucosa by a double (outer longitudinal and inner circular) layer of smooth muscle fibres. Submucosa: It is composed of loose connective tissue containing blood vessels and a nerve plexus—Meissner’s plexus, in which some gangilion cells may be found. The glands of Brunner (Duodenal glands) occur in the duodenum. Muscularis externa: It is composed of two layers of muscular 52 DIGESTIVE TRACT tissue, an outer thinner longitudinal and an inner thicker circular. Between them lies a nerve plexus— the plexus of Auerbach. Serosa: It is composed of a thin layer of loose connective tissue with mesothelium. Slide 30 Jejunum ( Small Intestine ) H.E. The wall of the jejunum also consists of four layers. The villi are well developed. The intestinal glands are similar to those of the duodenum. Goblet cells are interspersed with absorptive cells. In the lamina propria connective tissue, lymphatic tissues sometime are aggregated here and there into an isolate nodule. Slide 31 Ileum ( Small Intestine ) H.E The wall of the ileum also consists of four layers. Goblet cells are plentiful. But in the lamina propria connective tissue, lymphatic tissues are aggregated here and there into nodules. The nodules constitute, when they occur agglomerated, known as Peyer’s patches. They occur more often in the antimesenteric region (away from the mesentery) of the intestine. Slide 32 Colon ( Large Intestine ) H.E. The large intestine has usual four coats, except near its termination 53 DIGESTIVE TRACT where the serosa is absent. But it absence of any villi. The mucosa of colon is lined by simple columnar epithelium, but containing more goblet cells, abundant crypts of Lieberkuhn and a cellular lamina propria. Lymphatic nodules may be found in the lamina propria. The external border of the mucosa is marked by a thin muscularis mucosa. The submucosa is composed of connective tissue, blood vessels and Meissner’s plexus. The muscularis externa consists of an inner circular and outer longitudinar layers. The inner circular layer is thick and well developed, while the outer longitudinal muscular fibres are gathered up into three thickened bands—taenia coli. Between these bundles the muscle coat spreads to form a thin layer. Slide 33 Appendix (Large Intestine) H.E. The lumen of the appendix usually contains masses of dead cell debris. Absence of any cilli. The glands are fewer. The lining cells are simple columnar, containing only few goblet cells. The lamina propria is heavily infiltrated with leucocytes which have the appearance of lymphatic nodules. Lymphoid tissue highly developed in submucosa. The muscularis externa consists of the usual inner circular and outer longitudinal layers. Muscular coats thick. A serosa is present. 54 DIGESTIVE GLAND DIGESTIVE GLANDS Objectives: To understand the structural features of salivary gland. To grasp the morphological features of liver, pancreas. Slide 35 Parotid Gland ( Salivary Gland ) H.E. The parotid gland is surrounded by a capsule of connective tissue, which extend into the parenchyma and divides it into lobes and lobules. Each small lobule is formed of a group of irregularly saccular or tubular alveoli from which a small duct passes, and this unites with other to form larger ducts. The parotid glands are composed of serous only. Note that the acinar cells have spherical nuclei situated toward the base of the cells. The intercalated ducts, and striated ducts are present in the lobules also called intralobular ducts. The ducts in the septa are called excretory ducts or extralobular ducts. The intercalated ducts are lined by simple squamous epitheliun. The lining epithelium of striated ducts and excretory ducts range from simple columnar 55 DIGESTIVE GLAND to pseudostratified. Slide 36 Submandibular Gland ( Saliary Gland ) H.E. The submandibular gland is a mixed gland; both serous and mucous alveoli (the latter have crescents) are present, although serous alveoli predomonant. The structure of the gland is similar to the parotid gland except for the presence of mucous secreting cells and demilunes. Identify also the intercalated and striated ducts. Slide 37 Sublingual Gland ( Saliary Gland ) H.E. The sublingual gland is a mixed gland, but mucous alveoli are more numerous. Many of these show crecsents at their margins. Pure serous acini are rare. The mucous alveoli being larger, more uniform in shape. There is no capsule surrounding the sublingual gland. The intercalated duct is short, therefore it is difficult to find in this gland. Slide 34 Pancreas H.E. The pancreas consists of lobules separated by loose connective tissue, which contain blood vessels, lymphatics, nerves 56 DIGESTIVE GLAND and also branches of duct system. The pancreatic lobules are made up of large number of serous acini, separated by a minimal amount of connective tissue. Within the lobules there occur scattered throughout the gland small irregular masses of paler stain cells. These are the islets of Langerhans. The cells which line the alveoli are columnar or polyhedral in shape. The lumen of the acinus is small, and is difficult to see in many cases. Myoepithelial cells are not present. The basal cytoplalsm of the acinar cells is strongly basophilic. The apical cytoplasm is acidophilic due to the present of zymogen granules. In the centre of each acinus there may generally be seen a few nuclei. These are nuclei of centroacinar cells. They apear to be continued from the cells which line the smallest ducts. Examine the duct system. The smallest branches of the duct are centroacinar cells. The intercalated ducts are small ducts, lined by three or four low cuboidal cells in section. Compare the intercalated ducts with the capillaries. The intralobular ducts are more numerous in section. It is to be found within the lobules of the pancreas. The lumen is wide and lined by cuboidal or low columnar cells. The interlobular ducts ocour in the septa between lobules.The lumen is lined by columnar epithelium in which goblet cells may be found. The duct is surrounded by a thin layer of connective tissue. 57 DIGESTIVE GLAND Islets of Langerhans are the endocrine portion of the pancreas. The islets contain four kinds of cells—A, B,D and PP cells. These cell type can only be distinguished by special stain such as Mallory-azan and under the electron microseope. You won’t be able to distinguish them apart from your H.E. preparation. The islets is rich in blood supply. Slide 2 Liver H.E. Under low power, note there is a layer of connective tissue underneath the serosa covering of the liver, forming an external capsule to the organ. The connective tissue extends into and divide mass of hepatic parenchymal cells into many roughly hexagonal shaped units called hepatic lobules. The centre of the lobule is marked by the central vein. Each central vein appears as a single empty space in the section although it is fillled with blood in life. The connective tissue between the liver lobules is called the interlobular septum. The region where interlobular septa of adjacent lobules meet, is called the portal area. Each portal area consists of branches of the hepatic artery; portal vein, a lymphatic vessel and a bile duct. Identify these structures in the portal area. Locate the central vein of the hepatic lobules; then search a shordistance from the central vein for the portal areas surrounding 58 DIGESTIVE GLAND the central vein; the area marked off by the portal areas is the hepatic lobule. Now examine the hepatic lobule in more detail. Note that hepatic lobule is made up of hepatic cords arranged as anastomosing plates radiating out from the central vein. The cytoplasm the hepatocytes is homogenous or vacuolated and eosinophilic. The nucleus is large, spherical, vesicular and with a well developed nucleolus. Most cells have a single nucleus but binucleate cells occur frequently. Between the cords or plates of hepatocytes are the sinusoids. Note that the walls of the sinusoids are lined partly by endothelial and partly by Kupffer cells. The nuclei of the endothelial cells are elongated and rather densely stained while those of the Kupffer cells are more oval and paler stained. Slide 38 Liver (Pig’s Liver) Mallory You will immediately notice that the hepatic lobules in the pig’s liver are well demarcated. The interlobular septa with blue color in the pig’s liver is well developed. In the portal areas, there are interlobular artery, interlobular vein and interlobular bile duct. The interlobular vessels and bile ducts exhibit numerous branches in the liver parenchyma. Thus, in a cross section of the liver lobule, it is possible to see more than one section of each of these 59 DIGESTIVE GLAND structures whin a portal area. Slide74 Kupffer Cells ( Rabbit’s Liver ) H.E. Kupffer cells can be readily identified in this section of liver which was previously injected with trypan blue (or India ink). The Kupffer cells have phagocytosed the trypan blue (or carbon particles) which can be seen in the cytoplasm of the Kupffer cells in the sinusoids. The phagocytic Kupffer cells are large with several processes, and exhibit an irregular or stellate outline. Slide 64 Glycogen ( Liver ) Bestcarmine The glycogen of liver can be examined on this section. The glycogen granules are showed as red granules and an irregular distribution within the cytoplasm. Slide 39 Bile Canaliculi ( Liver ) Silver Examine this section. The bile canaliculi are showed with a special silver techniques. The bile canaliculi appear delicate filaments with brown-black colour between individual cells in the hepatic plates. Slide 67 Gall Bladder H.E. The mucosa exhibits temporary folds, which disappear when 60 DIGESTIVE GLAND the gallbladder is distended with bile. So the lumen of it in this section is irregular due to the folds. The crypts or diverticula between the folds ofen form deep indentations in the mucosa. They reaemble tubular glands in the lamina propria; however, there are no glands in the gallbladder proper (escept in the neck region). The mucosa is composed of the simple columnar epithelium without goblet cells, and lamina propria containing loose connective tissue and some diffuse lymphatic tissue. The muscularis is a thin layer with loose connective tissue that are rich in elastic fibers. The serosa is the outermost layer and covers all of these structures except the hepatic, where an adventitia attaches it to the liver. Slide 63 Human Soft Palate H.E. This is the sagittal section of the soft palate. The central support of the soft palate is a sheet of skeletal muscle. On the oral surface, the palate is covered by typical oral mucosa lined by stratified squmous nonkeratinized epithelium. The submucosa is characterized by the presence of mucous gland. On the nasal side, the soft palate is covered by the pseudostratified ciliated columnar epithelium of the nasal cavity. The lamina propria of the epithelium also contains a few glands. 61 ENDOCRINE SYSTEM ENDOCRINE SYSTEM Objectives: To grasp the morphological features of thyroid gland, adrenal gland, pituitary gland (hypophysis). To understand parathyroid gland. Slide 42 Thyroid H.E. The thyroid tissue is composed of follicles, which are irregular, spherical structure, grouped together by connective tissue septa. The follicles are variable in size. The wall of follicles is made up of simple cuboidal epithelium and the lumen contains red homogeneous colloid material. the There are many blood capillaries and clusters of interfollicular cells between the follicles. The parafollicular cells are frequently polygonal in shape and are large in size, the cytoplasm reveal pale with faintly stained round nucleus. These cells are often scattered among the follicular epithelial cells or gathered into groups between follicles. 62 ENDOCRINE SYSTEM Slide 43 Parathyroid H.E. The thin sheet of connective tissue encloses the gland and separates the gland from thyroid. The parenchyma glandular cells are arranged into cords or clusters with blood vessels and connective tissue between them. It is composed principally of chief cells. These cells are polygonal in shape, the cell boundaries are indistinct. The cytoplasm is faintly stained and only round nucleus can be seen easily. Many capillaries can be seen between cell clusters and cords. Slide 44 Adrenal Gland H.E. The peripheral red-stained portion of this specimen is adrenal cortex and central pale stained portion is adrenal medulla. Connective tissue capsule invests the whole gland. At lower magnification, the adrenal glands is seen to be divided into an outer cortex and inner medullar portions. Cortex: The cortex can be further divided into three zones according to the arrangement of the cells. Zona glomerulosa: A thinner layer lying beneath the capsule, contains smaller cells which are arranged in irregular ovoid clusters. The cytoplasm of these cells is often deeply-stained with only a few lipid droplets in it. 63 ENDOCRINE SYSTEM Zona fasciculata: A thicker layer occupies large part of the cortex. It consists of paralell cords of cells, which are polyhedral with a central nucleus. They are arranged in straight cords and contain a great number of lipid droplets in their cytoplasm. After the lipid contents in cytoplasm are dissolved out during specimen preparation, the fasciculated cells appear highly vacuolated. Zona reticularis: It is situated between zona fasciculata and medulla. It consists of irregular cord forming anastomosing network of closely packed clumps of cells. The cells are stained deeply. The 3 layers of the cortex are not demarcated clearly. Connective tissue and abundant capillaries settle among cell cords and cell clusters. Medulla: The cells are arranged in cords and clusters and have large granular nuclei. When fixing the adrenal gland in a fixative which contains chrome salts, the stored catecholamine granules in the medullary cells are oxidized to brown color, refered to as the chromaffin cells. In medulla, the central vein and its attributive branches can often be seen. Sometimes a few dispersed sympathetic ganglion cells can be identified. 64 ENDOCRINE SYSTEM Slide 46 Pituitary Gland ( Hypophysis ) Mallory This is sagittal section through the pituitary. The deeply-stained portion is pars distalis and the small faintly-stained portion is pars nervosa. The poorly narrow portion between them is pars intermedia. 1. Pars distalis: The pars distalis is the largest part of the gland, the cells are usually grouped in cords or clusteres which are intimate contact with extensive sinusoidal capillary network. On the basis of stainbility, it can be divided into 3 types, and cells of same type are frequently gathered together. Acidophils (alpha cells): They are large in size and coloured red. Mostly are polyhedral or irregular in shape with round nuclei. They can easily be distinguished from the remainder by virtue of densely packed red granules in their cytoplasm. Basophils (beta cells): They are lesser in number and tend to be a little large than acidophils. The basophils are ovoid or polyhedral cells. They have ronud nuclei. The cytoplasmic granules are basophil and coloured bluish purple. Chromophobes (c cells): They are the most numerous cells in pars distalis. They are small, round or polygonal cells. Their cytoplasm is stained pale so that the cell boundaries are not easily visible. Round nuclei are seen in the central position of cells. 2. Pars nervosa: It consists primarily of nervosa tissue represented by non-myelinated axons of the hypothalamohypophyseal 65 ENDOCRINE SYSTEM tract. Distributed among these nerve fibres are specialized neuroglial cells termed pituicyte. The nuclei of pituicytes are round or ovoid in shap. Some pituicytes may contain brown pigments in their cytoplasm. A few bluish gray homogenous corpuscles i.e. Herring’s bodies disperse among the nerve fibers. 3. Pars intermedia: It is a narrow portion between pars distalis and pars nervosa, which consists of small and pale staining cells. Several follicles varies in size and are lined by simple cuboidal epithelium. Slide 45 Pituitary Gland ( Hypophysis ) H.E. The pars distalis is the largest part of the hypophysis and contains two main types of cells, chromphil cells and chromphoble cells. Numerous capillaries are visible here. The chromphil cells are subdivided into acidophils (alpha cells) and basophils (beta cells). The cytoplasm of chromophils stains red in acidophils and blue in basophils. The chromphoble cells exhibit a light-staining, homogeneous cytoplasm. They are normally smaller than the chromophils and are found in groups. The pars nervousa is stained lightly and characterized by unmyelinated nerve fibers and pituicytes. Oval nuclei of pituicytes are seen, but not the scanty cytoplasm. Numerous capillaries are presen. The pars intermedia contains colloid-filled cysts or vesicles. 66 RESPIRATORY SYSTEM RESPIRATORY SYSTEM Objectives: To grasp the morphological features of lungs and trachea Slide 5 Trachea H.E. The cross section of trachea is circular in shape. C-shaped blue colored tissue is tracheal cartilage. The wall of the tachea and the bronchi system can generally be divided into three layers: the mucosa which is the innermost layer; the middle layer or submucosa which contains glands and the adventitia, including the cartilage and the connective tissue outside the cartilage. The mucosa of the trachea is lined by pseudostratified ciliated epithelium with a red clear basement membrane. Beneath the epithelium is the lamina propria composed of dense fine connective tissue. It contains a large number of elastic fibers which appear as red dots, and glandular ducts, blood vessels as well as diffuse lymphatic tissue. The external border of the lamina propria is continuous with the submucosa. But there is no clear boundary between the submucosa and lamina propria. The submucosa contains many 67 RESPIRATORY SYSTEM mixed gland, small vessels, nerves, and loose connective tissue. The adventitia is composed of loose connective tissue and hyaline cartilage ring. In the membranous portion of the posterior wall of the trachea, there is no cartilage in adventitia, which is made up of connective tissue and circular smooth muscles. The glands of the submucosa may be penetrated into adventitia. Slide 40 Lung H.E. In some samples, the pleura, which contains of mesothelium and a thin layer of connective tissue, can be seen. Under the pleura there is the pulmonary parenchyma, which contains numerous alveoli and bronchi in various sizes. Around bronchi there are some connective tissue in which blood vessels and nerves can be encountered. The thin tissue between the alveoli is called the alveolar septa. Intrapulmonary bronchus also possesses 3 layers as in trachea, but its dimension and wall become smaller and thinner. Pseudostratified ciliated epithelium becomes relatively thin, but bundles of smooth muscle outside lamina propria are prominent. Glands in submucosa diminish. Cartilage in adverntitia changes into several pieces of various size. Bronchioles are canal with narrow and irregular folded 68 RESPIRATORY SYSTEM lumen. Its epithelium is pseudostratified ciliated columnar epithelium or simple ciliated columnar epithelium. Goblet cells can occassionally be seen. Outside lamina propria, there is a circular layer of smooth muscles. Cartilage pieces disappear. Terminal bronchioles: The caliber is smaller. The wall is thinner, and the lumen is irregular in starlike appearance. Their epithelium is simple ciliated columnar in type, but in some cells, the cilia are disappeared. In the wall of a terminal bronchiole, goblet cell, cartilage and gland disappear, and outside lamina propria a layer of circular smooth muscle can be seen. Respiratory bronchioles: Respiratory bronchioles resembles the terminal bronchioles in structure except that their walls are interrupted by numerous alveoli or connected with the alveolar ducts. The form of the epithelium is simple columnar or cuboidal epithelium and transforms into simple squamous epithelium at alveolar openings. It contains some smooth muscle and connective tissue outside the epithelium. Alveolar ducts: Alveolar ducts may be surrounded by several alveoli or alveolar sacs. Their walls become discontinuous and consist of a succession of alveoli, the mouths of which are outlined by thin connective tissue and network of smooth muscle. They appear as knobs between adjacent alveoli. Alveolar Sac: It is the terminal portion of alveolar duct with several alveoli opening into it , but the terminal portion of 69 RESPIRATORY SYSTEM alveolalr septa has no knobs. Alveoli: In the pulmonary parenchyma, numerous saclike alveoli with irregular forms, varied in size, can be seen. Between the alveoli there are alveolar septa. The surface of the alveoli is lined with simple squamous cells (type I cells) and secretory cells (type II cells). The squamous cells are extremely thin and even not be distinguished. The flattened alveolar type I cells form the main lining of the alveolar wall. It has an elongate nucleus, and its cytoplasm is not clearly visible in the light microscope. The cuboidal alveolar type II cell with abundant vacuolated cytoplasm, occurs either singly or in groups between alveolar type I cells. Their nuclei are rounded and located in the center of the cells. Alveolar septa: It consists of two thin squamous epithelial layers between which lie capillaries and few connective tissue with some macrophages. The alveolar septa possese abundant network of blood capillaries, which tightly attach to the alveolar epithelium. Macrophage (dust cells): This cells are ovoid or irregular in shape. Their nucleus is round in the centre, but often masked by the granules. Its cytoplasm is red stained and filled with numerous engulfed dark brown granules. 70 URINARY SYSTEM URINARY SYSTEM Objectives: To grasp the morphological features of kidney; To understand the morphological features of urinary bladder and ureter. Slide 41 Kidney H.E. The red outer portion is cortex and the light inner portion is medulla. Sometimes deeply stained renal column may be seen on side of renal pyramid. The cortex is covered by a renal capsule, composed of a very thin dense connective tissue. Pay attention to distinguish the cortical labyrinth and medullary rays in cortex: The cortical labyrinth is the region where renal corpuscles and sections of convoluted tubules are located, while the medullary rays are straight tubules which arranged parallely and grouped into a bundle. The medulla consists of straight tubules often oblique or longitudinal sectioned. At the junction of cortex and medulla, 71 URINARY SYSTEM sections of arcuate artery can be seen. In the cortical labyrith the renal corpuscles are the most distinctive components of the cortex. The center of each renal corpuscle consists of a cluster of capillary loops (the renal glomerulus). The wall of the corpuscle is lined with simple squamous epithelium (parietal layer of Bowman’s capsule). The glomerular basement membrane is interposed between the capillary endothelium and the visceral layer of Bowman’s capsule. These two layers are difficult to distinguish from one another by light microscopy. Surrounding each corpuscle are many convoluted tubules. These are of two types: proximal convoluted and distal convoluted. The proximal convoluted tubules are numerous, have a relatively small, often uneven lumen and are composed of large broad cuboidal cells whose granular cytoplasm stains deeply with eosin. Brush borders are present but are not always well preserved in sections. The distal convoluted tubules are fewer in number, have a large regular lumen, the cells are smaller and more distinctly cuboidal, their cytoplasm stains less deeply and brush borders are not present. The medullary rays include three types of tubules. The straight (descending) segments of proximal tubules are generally similar in structure to the convoluted parts of 72 URINARY SYSTEM proximal tubules. The straight (ascending) distal segments are generally similar in structure of distal convoluted tubules. Collecting tubules are distinct because of their lightly stained cuboidal cells with visible cell boundary. The parenchymal components of the medulla consists of collecting tubules which empty at the apex of the pyramid and ascending and descending thin limbs of Henle’s loop. The latter have a thin squamous epithelial lining similar to the endothelium of capillaries. Capillaries can be singled out by the erythrocytes in their lumen. Near the corticomedullary border, the ascending limbs of Henle’s loop are lined by taller, cuboidal epithelial cells. Juxtaglomerular Cells Look for renal corpuscle. At vascular pole, near the renal corpuscle, the smooth muscle cells of the afferent arteriole become hypertrophic and modified into epithelioid cells. The nuclei are relatively large, and round or ovoid shape with fine chromatin. There are a great number of purple stained granules in cytoplasm. Macula Densa At the point that the distal convoluted tubule is in contacted with the vascular pole of the renal corpuscle, the epithelial cells of the tubule become narrower and taller and turn columnar. Their 73 URINARY SYSTEM nuclei are closely packed together, forming the macula densa, the cell boundaries are relatively distinct. Slide 69 Ureter H.E. The undistended ureter has a small and irregular lumen, the convolution being due to longitudinal mucosal folds. The mucosa consists of transitional epithelium, and lamina propria of connective tissue. The muscle layer consists of an inner longitudinal layer and an outer circular layer of smooth muscle. The advantitia is made up of loose connective tissue and continuous with surrounding connective tissue. Slide 66 Urinary Bladder H.E. The mucosa is made of transitional epithelium and lamina propria. The most characteristic feature of the transitional epithelium is the presence of large bulging cells in the superficial layer. In distendend bladder the superficial cells are flate and thin. The muscularis is a thick coat. It is more or less in 3 layers: The inner is longitudinal and middle is circular and the outer is longitudinal. But these 3 layers often intermingled with each other and are difficult to distinguish. The advantitia is made of connective tissue. 74 MALE REPRODUCTIVE SYSTEM MALE REPRODUCTIVE SYSTEM Objectives: To grasp the morphological features of the Testis and Epididymis; To understand the structures of the prostate gland; To understand the structures of the ductus deferens. Slide 47 Testis H.E. Under low power note the testis is enclosed by a strong fibrous capsule, the tunica albuginea, containing sections through large arteries and veins in its inner most layer. The tunica albuginea is covered externally with a thin layer of serous epithelium. From its inner surface there proceed fibrous processes or trabeculae, which imperfectly subdivide the organ into lobules. Posteriorly the capsule is prolonged into the interior of the gland in the form of a mass of fibrous tissue, which is known as the mediastinum testis. Each lobule contains numerous sections 75 MALE REPRODUCTIVE SYSTEM of the highly convoluted seminiferous tubules. Using high power, the tissue reveals a variety of planes of section through the seminiferous tubules. The seminiferous tubules are formed of a connective tissue membrane. In the adult, the tubules contain several layers of epithelial cells. There are two cell types that can be identified. The sustentacular or Sertoli cells and the spermatogenic cells. The Sertoli cells here and there between the spermatogenic cells, they are enlarged, and project between the more internal layers. The cells have their oval or irregular shaped nuclei containing prominent nucleoli localized along the basement membrane. These are relatively few in number. The spermatogenic cells in various stages of development or differentiation can be found. The one next to the basement membrane is a stratum of clear cubical cells—spermatogonia, the most of nuclei exhibits the irregulalr network which is characteristic of the resting condition, but in some tubules the nuclei show indication of division. There are two main classes of spermatogonia: Type A have a spherical or ovoid nucleus containing fine chromatin granules and a nucleolus; Type B have a centrally located nucleus with heavily stained chromatin masses. Next to this lining epithelium is a zone of larger cells—primary spermatocytes. They have large nuclei and large 76 MALE REPRODUCTIVE SYSTEM cell volume. Their nuclei reveal variable appearance due to the different states of activity of the chromatin usually at the pachytene stage. The secondary spermatocytes are not frequently encounted and less readily identified. Next to them, and most internal, are to be seen as the result of this division a large number of small cells with simple spherical nuclei—spermatid. The spermatozoa lie in groups, their heads lie in the recesses of the cytoplasm of Sertoli cells. Their tails project into the lumen of the tubule. Between the seminiferous tubules, the connective tissue contains blood vessels, lymph vessels, nerve and the usual connective elements. In addition, clusters of epithelioid cells, the interstitial cells (Leydig cells) are also present. They are larger and more rounded than other cells between the seminiferous tubules with eosinophilic cytoplasm. Slide 47 Epididymis H.E. The epididymis can be seen in the same section of the testis. The epididymis is located on the posterior-superior surface of the testis. The proximal part, or head of the epididymis is formed by the ductuli efferentes which joins the rete testis. The epithelium 77 MALE REPRODUCTIVE SYSTEM of the ductuli efferentes is simple, consisting of alternating groups of high ciliated columnar cells and shorter nonciliated cells , which are believed to be absorptive. The basal surface of the ductuli has a smooth contour. Locatde under the basement membrane is a thin layer of connective tissue containing a thin layer of circularly arranged smooth muscle fibers. The body and tail of the epididymis is formed by the ductus epididymis. The duct is a long, highly convoluted tubule, which is lined by a pseudostratified epithelium of tall columnar cells with long, nonmotile stereocilia and small basal cells. The epithelium is surrounded by the basement membrane, connective tissue containing circular smooth muscle and many blood vessels. Spermatozoa can be seen in the lumina of some of the tubules. Slide Vas Deferens H.E. The vas deferens is a thick-walled tube. Note the extremely well development of the muscular coat, having three layers: The inner and outer layers are made up of longitudinal bundles of smooth muscles, the wide middle layer of circular fibers. There is a good deal of connective and elastic tissue between the muscle bundles. The tube is lined by a mucous membrane, the inner surface of which is covered by pseudostratified columnar non-ciliated epithelium. 78 MALE REPRODUCTIVE SYSTEM Slide 48 Prostate H.E. The prostate is a tubuloacinar gland. It is composed of many glandular acini in a stroma of connective tissue and smooth muscle. The acini vary in size. The larger-sized acini exhibit wide, irregular lumina. The folded walls of acini are lined by simple cuboidal or columnar cells. In older people, the acini often contain colloid prostatic concretion, which may undergo calcification. 79 FEMALE REPRODUCTIVE SYSTEM FEMALE REPRODUCTIVE SYSTEM Objectives: To grasp the morphological features of ovaries and uterus; To understand the structures of the oviduct; To understand the structures of the mammaty gland. Slide 75 Ovary H.E. Under the low power examine the ovary is covered by a single layer of flat epithelial cells. Beneath the epithelium there is a layer of thick connective tissue—the tunica albuginea. Identify the medullary region, containing several blood vessels and a small amount of loose connective tissue. This is surrounded by a thick cortex. There are no sharp limits between the cortex and medulla. The stroma of the cortex is composed of characteristic 80 FEMALE REPRODUCTIVE SYSTEM spindle-shaped connective cells. Scattered throughout the stroma are follicles of different sizes, the smallest being near the surface to the organ, the larger ones placed more deeply in the stroma. Two types of folliclels can be distinguished: primordial follicles and growing follicles. The primordial follicles are located in the periphery of the cortex and under the tunic albuginea. They are the smallest and simplest in structure. Each primordial follicle consists of a primary oocyte enveloped by a single layer of flattened follicular cells. The growing follicles are subdivided into two stages—the primary follicles and secondary follicles.. Find the various stages of development of the follicles and look for the following features: 1. Oocytes is a primary oocyte. 2. Zona pellucida is the noncellular glycoprotein layer surrounding oocyte. It appears pink. 3. Follicular cells change to simple cuboidal or columnar, even more layers which are called as granulosa cells. 4. Corona radiata are a single layer and more columnar than the other granulosa cells. They are attached radially to the zona pellucida. Follicular antrum appears and is filled with follicular fluid. (Larger follicles with antral cavities of various sizes are called 81 FEMALE REPRODUCTIVE SYSTEM as secondary follicles). Stratum granulosa refers to the cells which consist of the wall of follicles. Cumulus oophorus is located on one side of the follicle and projects into the antrum with oocyte, zona pellucida, and corona radiata. 5. Theca interna and theca externa differentiated by stromal cells surround the follicles. The theca interna is an inner layer of vascularized, secretory cells. The theca externa is an outer layer of connective tissue cells. Between the follicles there are some atretic follicles in which degenerating oocytes can be seen. Scattered between follicles, there are groups of round cells with foamy of pink-stained cytoplasm. These are interstitial cells, which are probably derived from theca of atretic follicles. This section do not well show the structures of the corpus luteum. Slide 49 Ovary H.E. Examine the corpus luteum. They consist of the granulosa lutein cells, which are the hypertrophied granulosa cells of the follicle, and the theca lutein cells, fromed from the theca interna cells of the follicle. The granulosa lutein cells constitute the 82 FEMALE REPRODUCTIVE SYSTEM mass of the corpus luteum. These cells are large, have large vesicular nuclei, and stain lightly because of lipid inclusions. The theca lutein cells are smaller than granulosa lutein cells, their cytoplasm stains deeper and their nuclei are smaller and darker. Numerous capillaries and fine connective tissue septa are visible between the lutein cells. The stroma around the corpus luteum is highly vascular. Slide 50 Uterus ( Proliferative Phase ) H.E. The body of the uterus is formed of the following three layers: 1. Serosa ( perimetrium ): which covers the greater part of the fundus. 2. Myometrium: which is of great thickness and is formed of smooth muscle fibres disposed in three or four layers, which are not well defined: the stratum submucosum, the stratum vasculare, the stratum supravasculare, and the stratum subserosum. The first and the forth are composed mainly of fibres disposed longitucdinally. The stratum vasculare has many large blood vessels. In this layer, has circular and obligue muscle bundles. 3. The endometrium consists of epithelium and lamina propria containing long, simple, tubular glands—uterine glands. 83 FEMALE REPRODUCTIVE SYSTEM The epithelial cells are simple columnar and are a mixture of ciliated and secretory cells. The uterine glands is similar to the superficial epithelium. The connective tissue of the lamina propria contains a large number of spindle-shaped cells. Connective tissue fibres are rare. Pay special attention should be: (1) thickness of the endometrium ; (2) interlacing of the endometrium and myometriun at their junction; (3) height and character of the lining epithelium; (4) number, length, diameter and shape of glands; (5) the close packing of the stroma cells and the position and shape of the blood vessels. Slide 68 Oviduct H.E. The wall of the oviduct is composed of three layers: The mucosa has long longitudinal folds. The epithelium lining the mucosa is simple columnar and contains two types of cells. One is provided with cilia and the other is devoid of cilia and appears to be secretory. The lamina propria of the mucosa is composed of loose connective tissue. The muscular layer is composed of a thin longitudianl layer of smooth muscle fibres and an outer thicker circular smooth muscle 84 FEMALE REPRODUCTIVE SYSTEM fibres. Externally the tube is covered by a serosa—connective tissue and mesothelium. Slide Mammary Gland ( Resting Breast ) H.E. The resting gland consists mainly of connective tissue and scattered groups of excretory ducts with branches which terminate in collapsed alveoli or solid cell cords. Slide Mammary Gland ( Lactating Breast) H.E. In this section, the connective tissue is reduced to thin septa which enclose large lobules of densely packed ducts and alveole which are actively secreting. The alveolar epithelium is composed of low columnar cells, secretory droplets accumulate in the apical cytoplasm, while the nucleus is displaced basally. 85 SKIN SKIN Objectives: To grasp the five-layer structures of epidermis; To grasp the hair, hair follicle and hair bulb; To understand the structures of the sebaceous gland, arrector pelli, sweet glands. Slide 19 Skin ( Finger ) H.E. Under low power, note the skin is composed of two parts, the outer epithelial layer, the epidermis and inner dense connective tissue layer, the dermis. Beneath the dermis is a loose connective layer, the hypodermis, containing many fat cells, large bundles of nerves and Pacinian corpuscles (lamellated corpusles). The epidermis is keratinized stratified squamous epithelium. It contains no blood vessels. The nourishment of the cells is derived from vessels of the dermis through diffusion. The epidermal-dermal junction is wavy, due to projections of the dermis SKIN 86 (dermal papillae) into the under surface of the epidermis. For descriptive purposes, the epidermis can be distinguished into five layers. 1. Stratum basale (S. germinativus). This is a single layer of cells, the deepest cells of the epithelium, which are set on the surface of the dermis, are columnar, cuboidal, even squamous in shape. The cytoplasm is stained brownish, exhibited pigment (melanin) granules in these cells (especially in the darker parts of the skin). Many of the cells show mitosis, an indication that the epidermis is regenerated from these cells. 2. Stratum spinosum or prickle cell layer. Immediately above the basal layer is stratum spinosum. This layer is three to four cells thick. The cells of stratum spinosum are closely packed, polyhedral form. Between the cells there are fine intercellular clefts separating the cells from one another. All the cells bear short cytoplasmic process which called intercellular bridges. The cells of this layer are basophilic, contain various amount of cytoplasmic fibrils or keratin. Cell divisions occur in this layer, and occasional mitotic figures can be seen. 3. Stratum granulosum. This layer is formed of 2~5 layers somewhat flattened cells filled with granules or droplets of material (eleidin) staining deeply with carmine and hematoxylin. These cells form an irregular layer. 4. Stratum lucidum. Superficial to the stratum grenulosum SKIN 87 is a layer in which the cell-outlines are indistinct and the cells contain flakes or larger droplets of a hyaline material, kerato-hyalin, staining less intensely than the granules in the last layer, and tending to run together. This layer has a clear appearance in section, but is absent in thinner skin. 5. Stratum corneum. Immediately superficial to the stratum lucidum is the cornified cells of the epidermis. It is composed of a number of layers of flattened, dead cells, the nuclei of which are no longer visible, the cytoplasm js packed with keratin. The stratum basale and spinosum are often grouped together collectively as the stratum Malpighi The dermis is composed of dense connective tissue. It can be subdivided into: 1. Superficial or papillary layer is connective tissue that consitutes dermal papillae; these project into the epidermis, which is moulded over and attached to them. The papillary layer consists mainly of fine collagenous fibres, reticular fibres and elastic fibres interweaving with blood vessels. Some papillae may contain special sensory terminations—Meissner’s corpuscle (tactil corpucles) 2. The reticular layer consists mainly of bundles of coarse collagenous fibres running in various directions but mainly parallel to the surface. It also contains extensive network of blood vessels, nerves and lymphatics. SKIN 88 Below the dermis and likewise not sharply differentiated from it is the subcutaneous connective tissue (superficial fascia) which serves to bind the integument to the underling organs. This layer contains connective tissue, often heavily infiltrated with adipose tissue. Slide 26 Scalp ( Human Scalp ) H.E. The hair follicles can be seen in black-purple stain, hair shafts are exposed near the surface of the skin or may be cut off. The fundamental structure of the scalp is similar to that of palmar skin, but the epidermis is especially thinner. The stratum cornum consists merely of several layers of keratinized cells. The stratum basale contains more brown pigments. The dermis is thicker and hairs, arrector pelli muscle, sebaceous glands and sweet glands are located in it. The hair and its follicle: Each hair consists of a hair shaft which projects above the surface and a root which is embeded within its distal deep portion and a hair follicle. The hair is composed of keratinized cells stained in red, pigment granules are found in and between the cells. The hair follicle is made up of epithelium and connective tissue. The epithelial sheath is divided into an internal root sheath and outer root sheath.The internal root sheath is stained in red. Their cells are corresponding to the SKIN 89 stratum corneum of the epidermis. The outer root sheath is corresponding to the stratum spinosum and basale of the epidermis. The connective tissue sheath is similar to the dermis. In some longitudinal section of the hair, the terminal dilatation callled the hair bulb, which the connective papillar projects in, can be seen. The arrector pili consist of smooth muscle cells gathered into a bundle, which bunds to the connective tissue sheath of the hair follicle and connects it to the papillary layer of the dermis. The sebaceous glands are attached to the upper of the hair follicle. The cells comprising the sebaceous secretory unit are characterized by a centrally located nucleus and a pale staining, vaculated cytoplasm. The excretory ducts are lined by stratified squamous epithelium continuous with the epidermis. SENSORT ORGAN SENSORY ORGAN 90 Objectives: To understand the structures of eye ball; To grasp the morphological features of cornea; To understand the morphological features of lens, retina, eyelid; To understand the structures of the inner ear; To grasp the morphology and structure of spiral organ (Organ of Corti). Slide 51 Eye Ball H.E. The eye ball consists of the wall of the eye ball and refractive media. The wall of eye ball is composed of 3 tunics, from outside to inward are: tunica fibrosa, tunica vasculosa and retina. The refractive media includes vitreous body, lens and aqueous humor. Tunica fibrosa is the outermost red stained layer and is divided into 2 parts: the cornea and the sclera. Cornea is the slightly bulged anterior part. It is composed of five layers. From anterior to posterior: SENSORT ORGAN 91 Cornea is the slightly bulged anterior part. It is composed of five layers. From anterior to posterior: 1. the cornea epithelium is a thin layer of nonkeratinized stratified squamous epithelium, and consists of 5 to 6 layers of cells. 2. Bowman’s membrane (anterior limiting membrane) is a homogeneous layer beneath the epithilium. 3. the substantia propria is the thickest layer and formed by several sheets of regularly arranged collagenous fibers, the fibroblasts lie between collagenous fibre sheets, no blood vessel is there. 4. Descemet’s membrane (posterior limiting membrane) is also a homogeneous layer, and lies internal to the substantia propria. 5. Endothelium is simple squamous epithelium on the posterior surface of cornea. Sclera is the posterior five sixth of the external layer of the eye. It consists of dense fibrous connective tissue made up mainly of flat collagenous bundles. Few fibroblasts and pigment cells scatter between fibre bundles. Tunica vasculosa is the brownish colored tunic inside tunica fibrosa, and this tunic is divided into 3 parts again: choroid, ciliary body and iris. Choroid is the posterior part of this tunic, closely applied to SENSORT ORGAN 92 the interior of sclera. It is composed of loose connecrtive tissue and contains many blood vesseels and pigment cells. Ciliary body is an anterior thickened portion of tunica vasculosa, triangulalr in shape in section and situated just behind the cornea scleral junction. In the inner side of anterior portion of ciliary body, there are many folds or processes, which is ciliary processes. The main part of ciliary body is composed of loose connective tissue with blood vessels, pigment cells and well-developed ciliary muscle. This muscle is composed of 3 bundles of smooth muscle fibers in defferent directions. Two layers of cuboidal cells extending from the retina line the inner surface of the ciliary body, the outer layer is pigmented cells and the inner layer is free of pigment. Iris is a membranous extension of the ciliary body and partially covers the lens, its central aperture, the pupil. The iris is consists of a pigment, highly vascular connective tissue. The anterior surface is lined with endothelium. Its posterior surface is covered with a double layer of heavily pigment cuboidal epithelium. In the anterior layer of the epithelium, two groups of smooth muscle—the circular sphincter of the pupil and the radially arranged dilatator of the pupil can be seen. Retina lies close to the inner surface of the vascular layer. In cross section, from external to internal, the layers of the retina are as follows: SENSORT ORGAN 93 1. Pigment epithelium 2. Layer of rods and cones 3. External limiting membrane 4. Outer nuclear layer 5. Outer plexiform layer 6. Inner nuclear layer 7. Inner plexiform layer 8. Ganglion cell layer 9. Optic nerve fiber layer 10. Internal limiting membrane Lens: It lies behind the iris. It is ovoid in shape and is enveloped by a thin lens capsule. Under the anterior surface of the capsule there is a simple cuboidal epithelium named subcapsular epithelium. At the equatorial region of the lens, the epithelial cells elongate to form the lens fibers with an elongated nucleus in their center. The lens fibers arrange in a concentric fashion. In the central part of the lens, the nuclei of the lens fibers undergo degeneration and disappear at last. Vitreous body: It fills the space between the lens and retina. Anterior and posterior chambers: The space lies between the cornea and the lens is anterior chamber and that lies between vitreous and lens, iris as well as ciliary body is posterior chamber. The angle formed by the cornea with the basal part of the iris is SENSORT ORGAN 94 the iris angle or angle of the anterior chamber. Near ora serrata, the visual portion of retina become thin suddenly, and the layer of it also reduced in numbers, only 2 layer cells remain, and changes to the blind portion of retina. Optic papilla is the region all the nerve fibers of ganglion cells dissappear. The margin of the pupilla bulges inward and with its central part depressed. The area where optic nerve fibers cross the sclera is the area cribrosa. The nerve fibers gether into bundles and enveloped with comparatively dense connective tissue which is continous with sclera, and thus optic nerve is formed. Slide 70 Eyelid H.E. The outer surface of the eyelid is skin. It is thin with hair, sebaceous glands and sweat glands in the dermis. The sebaceous glands located near the palpebral maigin are small that is glands of Zeis. There are also composed of special sweat glands with large lumen—the glands of Moll as well as thick eyelashes without arrector pili muscle. The subcutaneous layer is a thin layer of loose conective tissue and is almost completely avoid of fat. The muscle layer consists of skeletal muscle—the orbicularis oculi muscle and the levator palpebrae muscle. SENSORT ORGAN 95 The tarsus is a plate of dense connective tissue which is the skeleton of the lid. In which the Meibomian glands are embeded. The Meibomian glands are sebaceous glands, the ducts of which open at the palpabral margin. The deep inner surface of tarsal plate is palpabral conjuctiva, which is composed of stratified columnar epithelium and contains some goblet cells occasionally. Its lamina propria is composed of connective tissue with numerous lymphocytes. Slide 52 Cochlea ( Inner Ear ) H.E. The pyramidal structure in the center of this section is the cochlea. The deeply stained area in the centre of cochlea is modiolus. On the both sides of modiolus, there are 3~4 small canals respectively, these are cross-section of osseous cochlea around the modiolus. The lumen of each osseous cochlea is devided into three cavities: an upper cavity—the vestibuli; lower cavity—the seala tympani; and an intermediate cavity—the cochlear duct. The modiolus is composed of spongy bone, and contains blood vessels and spiral ganglion. Form the modiolus a shelf of bone projects toward the lumen of the osseous canal of the cochlea. That is the osseous spiral lamina. Blood vessels and spiral ganglion are located in its basal portion. SENSORT ORGAN 96 The cochlear duct: The osseous spiral lamina is continous outward with a membranous spiral lamina. The cochlear periosteum become thickened at its outer attachmentas the spiral ligament to form complete transverse septum. A thin membrane, which extends obliquely from the osseous spiral lamina to the upper part of the spiral ligment, is the vestibular membrane. Thus the cochlear duct has 3 walls: The upper wall—vestibular membrane; the outer wall—the spiral ligament; and the lower wall—basilar membrane. The vestibular membrane is composed of very thin layer of connective tissue and covered by simple squamous epithelium on both sides. The spiral ligament is in contact with lateral bony wall and is composed of thickened connective tissue covered by pseudostratified columnar epithelium. This epithelium is rich in blood vessels and is called stria vascularis. The lower wall is higher and irregular limbus, from which derives a glycoprotein structures—the tectorial membrane. Spiral organ (Organ of Corti) lies on upper side of basilar membrane. Spiral organ (Organ of Corti). The membranous spiral lamina is composed of 3 layers: a central basilar membrane in which contains auditory strings is covered by epithelium in both of its superior and inferior surfaces. The inferior epithelium is a thin layer of squamuous epithelium continuous with that lining the scale tympani. The superior epithelium becomes thickened SENSORT ORGAN 97 and differentiates into the spiral organ which contain several types of cells. Two main cell types is divided — the supporting cells and the hair cells. The supporting cells: According to their morphology. Inner and outer pillar cells: They are tall and the basal portions of the cells are border which situated on the basal membrane. Apical end and basal portion of these cells interlock and form a triangular space —inner tunnel. Nuclei of these cells are round, and situated in basal portion of cells,deeply stained. Inner and outer phalangeal cells: The inner phalangeal cells are arranged in a row along the inner surface of the inner pillar cells. The inner hair cells are situated on them. The outer phalangeal cells are arranged along the outer surface of the outer pillar cells. Their number varies in different regions of the cochlear duct. It is 3 rows in the base of the cochlear duct and 5 rows in apex. The 3~5 rows of outer hair cells are rested on them. The inner and outer hair cells are supported by the inner and outer phalangeal cells, respectively. They are sensory cells. On the top of some hair cells, cilia can be seen. 98