Download Epithelial Tissue 1. Simple Squamous Epithelium 1.1 Section No.： 4

Epithelial
Tissue
1. Simple Squamous Epithelium
1.1 Section No.： 4
Material:frog’s mesentery
Staining：silver
Observed by Microscope(10x40)
The individual cell has hexagonal or irregular wavy outlines,and each contaihs
a nucleus,which is not shown in this slide.
1.2 Section No.： 39
Material: Kidney
Staining：H.E.
Observed by Microscope(10x10)
Lonking for the renal corpuscle under capsule ,which surrounded by a
double-walled epithelial capsule called renal capsule. The parietal layers of renal
capsule is simple squamous epithelium.
Observed by Microscope(10x40)
The epithelial cells are fusiform with deep-stained ovoid nuclei in center.
2. Simple Cuboilal Epithelium
Section No.：54
Material: thyroid
Staining: H.E.
Observed by Microscope(10x10)
There are many follicles,which are composed of simple cuboilal epithelium.
Observed by Microscope(10x40)
The epithelial cells appear as a circle of square profiles with round nuclei in center.
3. Simple Columnar Epithelium
Section No.：30
Material: crosssection of jejunum
Staining: H.E.
Observed by Microscope(10x10)
There are many intestinal vilius,which are finger-like projections of mucosa. The
surfaces of vili are covered by the simple columnar epithelium, which surfaces are
covered by striated border.
Observed by Microscope(10x40)
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 nucleis.
4. Pseudostratified Ciliated Columnar Epithelium
Section No.：37
Material: trachea
Staining: H.E.
Observed by Microscope(10x10)
This is a ring of transversally sectioned trachea with large central lumen.The
Thin bluish-purple colored layer lining the luminal surface is pseudostratified ciliated
columnar epithelium.This epithelium appears as multi-layered because of the presence
of nuclei at various levels.However all cells rest on a pink basement membrane which
is located between epithelium and connective tissue,some of them do not extend to the
luminal surface.
Observed by Microscope(10x40)
The epithelium consists of four types of cells:
Columnar cell:it is tall with ovoid nuclei at high level,which free surface
possesses regular cilia.
Fusiform cell:it is spindle in shape with oval nuclei at the mid portion of the cells.
Basal cell: it is pyramid-shaped in the basal portion of the cells,which apices do
not reach the free surface of the epithelium.
Goblet cell:it can be seen among the columnar cells.
5. Stratified Squemouse Epithelium
Section No.：67
Material: esophagus
Staining: H.E.
Observed by Microscope(10x10)
On the lumen side of the esophagus,you can to find non-keratinized stratified
squamous epithelium,which consists of many layers of epithelial cells.
Observed by Microscope(10x40)
Basal cells: one layer of cuboidal cells
Intermediate regions:several layers of polygonal –shaped cells
Superficial layer: more and more flattened to the surface.
6. Transitional Epithelium
Section No.：41
Material: bladder
Staining: H.E.
Observed by Microscope(10x10)
This is a section of a contracted bladder. The epithelium is composed of six to
seven layers of cells.
Observed by Microscope(10x40)
The surface cells are very large and cuboidal in shape, covering several deep
cells,which is called domelike cell with deep-acidophilic cytoplasm. Occasionally
contains two nuclei.
The intermediate regions:several layers of irregular polyhedral
cells .
The deepest layer of cells : one layer of cuboidal cells.
Connective Tissue
1. Loose connective
Proper
tissue
1.1 Section No.：8
Material: mesentery
Staining: orcein or aldehyde fuchshine
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.
Observed by Microscope(10x40)
Two types of fibers and two types of cells can be distinguished:
Collagen fibers: they are reddish in color, wavy stranded bundles of fiber of varied
thickness run in all directions.
Elastic fiber：they are stained in black,which normally appear straight but a where
breakage has occurred may appear waye due to elastic recoil.
Macrophages
are irregulary shaped cells, engulf and accumulate the dye in their
cytoplasm in the form of
trypan blue granules .
Fibroblast only the ovoid nucleus can be identified.
1.2 Section No.：29
Material: stomach
Staining: H.E.
The portion of gastric fundus stained lightly is loose
connective
tissue.It
occupies between the bluish-purple gastric mucosa and muscular layers.
Observed by Microscope(10x10)
The fibers are loosely arranged and variously sectioned.
Observed by Microscope(10x40)
The collagenous fibers are numerous,pinkish,while elastic fibers are hardly
distinguished.Among fibers,many cells containing bluish-purple ovoid nuclei are
fibroblasts.Ground substance is lost during preparation and only empty spaces left
between fibers and cells.
2. Dense Connective Tissue
Section No.：23
Material: fing skin
Staining: H.E.
Observed by Microscope(10x10)
Skin is composed of two parts,the outer epidermis and inner dermis.In the irregular
dense connective tissue of dermis,most of the field is occupied by pink-staining
fibers, a few flattened fibroblast nuclei (blue) are seen among the fibers.
3. Adipose Tissue
Section No.：23
Material: fing skin
Staining: H.E.
Observed by Microscope(10x10)
Beneath the dermis is the hyperdermis,containing many fat cells,fat cells are the
predominant cell present, the tissue is called adipose tissue.
Observed by Microscope(10x40)
Fat cells appear vacuolated cytoplasm due to the drops of lipid being dissolved
during section preparation.The nulei are small flattened in periphery.
4. Reticular Tissue
Section No.：
Material: Lymph node
Staining: silver
Observed by Microscope(10x10)
Reticular tissue consists of reticular cells and reticular fibers. The reticular fibers
look like fine, black threads. Between the numerous black lymphocytes,the reticular
cells are lightly yellow with some processes.
BLOOD
Slide 1
Blood Smear
Wright staining
Erythrocytes -- They are most numerous, they are biconcave disks without
nuclei.
Owing
to
their
richness
in
hemoglobin,
erythrocytes
are
red,
pale-pink-stained in the center.
Leukocytes -- These cells appear scattered randomly in a blood film, identifiable
by their basophilic nuclei. In normal blood there are 5 types of leukocytes of two
categories:
Neutrophils: They are the most numerous of white blood cells. Their cytoplasm
is slightly acidophilic with small, well-distributed 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 chromatin.
Basophils: They constitute about 0-1% of the total number of leukocytes and are
therefore difficult to be found. The cytoplasm contains numerous basophilic deep-blue
granules, which are different in size. The pale-stained nucleus is irrgular in shape and
always obscured by overlying granules.
Lymphocytes: They can be classified into 3 groups according to distinct size. The
small lymphocytes are the most commonly seen in blood smears, but medium-sized
lymphocytes and large lymphocytes are occasionally present. Each small lymphocyte
has a round, often with a slight indentation, deep-purple nucleus, which is surrounded
by thin rim of sky-blue-stained cytoplasm.
Monocytes:
They are the largest leukocytes, the nucleus is oval, kidney or
horseshoe in shape with delicately stained chromatin and the cytoplasm is slightly
grey-blue-stained.
Platelets
-- They often appear in small clusters among the blood cells.They are
small,disklike fragments of cytoplasm,each one has a peripheral light blue-stained
transparent zone and a central zone containing purple granules.
Reticulocytes
Brilliant Cresyl Blue Stain
Reticulocytes are the younger erythrocytes recently released by the bone marrow
into the blood stream.They may have a few granules or a netlike structure blue-stained
by brilliant cresyl blue in their cytoplasm.
Nerve Tissue
Slide 56
Neuron ( Spinal Cord )
H.E.
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
nucleus is large spherical and light stained, centrally located with a large, prominent
nucleolus. The cytoplasm is filled with Nissl bodies, which are stained as blue color.
Nissl bodies can also be seen in the dendrites. Find the axon hillock, a short
pyramid-shaped region, which contains no Nissl bodies, marks the site of origin of the
axon. Among the neurons, there are many neuroglial cells whose nuclei are obvious.
Slide 85
Synapse and Neurofibril
( Spinal Cord )
Silver staining
Neurofibril: Find a neuron with nucleus and processes in the ventral horn, many
dark brown filaments can be seen in the cell body and the processes(including axon
and dendrites), called neurofibril. The filaments are arranged reticulatly in the cell
body but they are parallel in the processes.
Synapse: Examine the neuron, sometimes we can see the enlarged axon terminal
showing as dark brown oval body, called synaptic knob on the surface of the cell body
or the dendrites.
Slide 11 Myelinated Fibers
( Sciatic Nerve)
H.E.
In the cross section of sciatic nerve, the nerve fibers are gathered up into round
bundles. The connective tissue connected the bundles and invested the whole nerve is
called epineurium. The connective tissue enveloped each bundle is known as the
perineurium. The delicate connective tissue, which lies between the nerve fibers of the
bundle, is termed epineurium. Nerve fiber is round, with a prunosus point (axis
cylinder) in the center, surrounded by white myelin sheath. The nuclei of schwann
cells can be seen in the margin of myelin sheath.
In the longitudinal section, a nerve fiber is made up of a central axis cylinder (a
process of a neuron), a sheath of myelin, a neurolemma. The nerve fiber is interrupted
at regular intervals where the neurolemma appears to produce constrictions, which are
called nodes of Ranvier. Schwann cells constitute the sheath and the neurolemma. The
pale oval nuclei can sometimes be seen.
Slide 15 Unmyelinated Fibers (Sympathetic Nerve Ganglion)
H.E.
The nerve ganglion is enveloped by the connective tissue. There are several large
neurons called ganglion cell surrounded by abundant satellite cells in the ganglion.
The non-myelinated fibers which are devoid of myelin sheath parallel with each other
and are pink stained.
Slide 23 Tactile Corpuscles, Lamellar Corpuscles, Nerve Fiber Bundles (Skin of
Finger Tip )
H.E.
Tactile corpuscles can be found in some of the dermal papillae of the skin. They
are ovoid in shape. The flattened cells of capsule are arranged in the form of
multipe-stacked lamellae. Unmyelinated nerve terminals enter the corpuscle, where
they branch and follow a spiral course among the connective tissue.
Lamellar corpuscles are large and located deep in the dermis and in 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.
Nerve fiber bundles are composed of a bundle of nerve fibers enveloped by
connective tissue. The nerve fibers look like red points when they are transected,
whereas
wavilness when they are longitudinally cut. Sometimes several small nerve
fiber bundles can be packaged into a bigger nerve fiber bundle by a connective tissue
capsule.
Slide 13 Motor End Plate ( Intercostal Muscle )
AuCl
This slide is a small piece of gold impregnated muscle press slide. Muscle fibers
are purple in color; myelinated fibers are stained black. A myelinated fiber will branch
before ending, and then each branch passes directly into the middle of a muscle fiber.
The axis-cylinder ends in a close terminal ramification with various expansions upon
its branches.
Slide 9 Astrocytes (Cerebrum)
Golgi’s
Method
Astrocytes are star-shaped cells with a large, oval nucleus. The processes of
astrocytes can expand to form end feet, attaching to the wall of blood capillaries
shown as irregular dark brown branches.
There are two forms of astrocytes: fibrous
astrocytes with few long processes in the white matter and protoplasmic astrocytes
with many short-branched processes in the grey matter.
CARTILAGE AND BONE
1. HYALINE CARTILAGE
Materials from: cross-section through the trachea
Slide number: 37
Staining: H.E
Observation: The blue-stained ring in the trachea wall is hyaline cartilage.
Using the lower objective lens (10×) to locate it. From the periphery to the
centre, the structures of hyaline cartilage would be found as follow:
⑴ Perichondrium: It is a layer of dense connective tissue covers the
cartilage. The outer layer of the perichondrium is rich in fibers, while the inner
layer of the perichondrium is rich in elongated cells.
⑵ Chondrocytes and matrix: The hyaline cartilage consists of a rather dense
amorphous ground substance in which is embedded by cartilage cells
(Chondrocytes) .
Chondrocytes are located in matrix lacunae. In living tissue, the
chondrocytes fill the lacunae completely, but sometimes small spaces appear
in the lacunae since the cytoplasm of chondrocyte tends to shrink after fixation.
At the periphery of hyaline cartilage, the chondrocytes have elliptic shape,
with their long axis parallel to the surface. At the inside of hyaline cartilage,
chondrocytes are round and most appear in isogenous groups. The matrix
immediately around each group is rich in chondroitin sulphate and may be
stained more deeply than the remainder.
The hyaline cartilage matrix contains collagen fibers, which is
indiscernible for 2 reasons: the collagen fibers have submicroscopic dimension;
and the refractive index of the fibers is almost the same as that of the ground
substance in which they are embedded.
Note that the cartilage is devoid of blood vessels.
2. ELASTIC CARTILAGE
Materials from: vertical-section of the ear pinna
Slide number: 7
Staining: Varrt Hoff’s staining+eosin
Observation: The ear pinna is covered by skin, elastic cartilage is located in
the center of the pinna. The cells are quite similar to those of hyaline cartilage.
Note the dense net work of darkmagenta staining elastic fibers, which fill the
matrix.
3. FIBROCARTILAGE （demonstration）
Materials from: Intervertebral Disc
Slide number: 77
Staining: H.E
Observation: Collagen fibers are the major constituent of this matrix. They
reveal as thick and compact collagenous bundles with pink color, paralleling
or interweaving with one another. The hyacinthine -stained chondrocytes are
ovoid in shape, small in size and arranged in rows. Isogenous groups are
seldom in this kind of cartilage.
4. COMPACT BONE (grind bone)
Materials from: transverse-section of human long bone
Slide number: 8
Observation: Calcified bone is too hard to be sectioned on a microtome. They
are cut as thin slices in transverse section with a saw and grind to the required
thickness with abrasives. Such sections show large numbers of bone lamellae,
which is consisted of the layered calcified matrix and collagen fibers. The
lamellae in the compact bones are regularly arranged in the three patterns:
circumferential
lamellae,
osteons
and
interstitial
lamellae.
Outer
circumferential lamellae and inner circumferential lamellae are located on the
external and inner surfaces of the long bone respectively. Osteons and
interstitial lamellae are located between outer and inner circumferential
lamellae.
⑴ Osteons( Haversian system):
They consist of:
①. A centrally located Haversian canal in which vessels, lymphatics, nerves
and connective are located at living period, which are filled with debris and
dye stain appear purple. The canal is communicated with Volkmann’s canal,
which carried the vascular and nerve supply from periosteum.
②. A series of concentrically arranged lamellae are the Haversian lamellae.
The bone lamellae are arranged in concentric layers around a central
Haversian canal. The bone lamellae fluctuate from 4 to 20 layers.
⑵ Interstitial lamellae: They are irregular lamellae, which occupy the intervals
between the Haversian systems.
⑶ Circumferential lamellae: The inner circumferential lamellae is thinner than
the outer, and it is incomplete (irregular ) .
There are a lot of dark ovoid lacunae between the lamellae or within the
lamellae where the osteocytes are placed. Many delicate cannels radiated from
the lacunae are canaliculi where the cytoplasmic processes of the osteocytes
project. The canaliculi in the adjacent lamellae are connecting with each other.
MUSCLE TISSUE
Muscle tissue is composed of muscle cells, with a little connective tissue
between them. Muscle cells are often termed muscle fibers because of their
elongated and thread-like shape, so they should be viewed in longitudinal and
cross sections. The membrane of muscle cells is referred to as the sarcolemma,
and the cytoplasm is termed sarcoplasm.
1. SKELETAL MUSCLE
Materials from: tongue
Slide number: 71
Staining: H.E
Observation: Skeletal muscle is a sort of striated muscle tissue.
Longitudinal section: The muscle fibers (cells) look like long belts. High
magnification of the cells show cross-striations of alternating light and dark
bands. The A bands are dark-stained bands. The I bands are lightly stained
bands. The bands are actually exhibited by the long myofibrils, which fill in
the sarcoplasm of skeletal muscle. Numerous nuclei can be seen in the
periphery of per cell, just under the cell membrane (sarcolemma).
Cross section：The cross sections of skeletal muscle are the round masses,
which are just among the longitudinal sections in this slide. The dots within
cells represent sections of myofibrils. The nuclei are located at the periphery
of the muscle fibers.
Emphasis: The features of the two sections, cross-striations, the number and
location of nuclei.
2. CARDIAC MUSCLE
Materials from: Heart
Slide number: 19, 73
Staining: 19-H.E, 73-Iron Hematoxylin
Observation: Cardiac muscle is also a sort of striated muscle tissue. In slide 19,
It is important to find the typical longitudinal section and cross section by the
lower objective lens (10×) at first.
Longitudinal section: In longitudinal section, the cardiac muscle fibers
differ from those of skeletal fibers in the following particulars.
⑴ The fibers are shorter and branched.
⑵ Their nuclei often lie near center of the fibers, and only one or two
nuclei in each fiber.
⑶ The cross striation (with A band, I band) are identical to those of
skeletal muscle, but their striations are less marked. By iron hematoxylin
staining (slide 73), the striations are prominent.
⑷ The fibers are interrupted by thin transverse lines-the intercalated
discs which is stained lightly darker than A bands. Intercalated discs are also
prominent in slide 73.
Cross section: The cardiac muscle fibers are round in shape with numerous
finely dotted in cytoplasm. The dots represent sections of the myofibrils of
which the fibers are composed. Large, ovoid nuclei, usually one per cell,
occupy the central position.
Emphasis: The feature of the two sections, cross-striations, intercalated discs,
the number and location of nuclei.
3. SMOOTH MUSCLE
Materials from: Stomach
Slide number: 74
Staining: H.E
Observation: Smooth muscle is a sort of unstriated muscle tissue. In the
stomach the muscularis is formed by several layers of smooth muscle fibers.
Smooth muscle cells are stained deeper than the connective tissue, arranged in
layers of different directions and so cut in both longitudinal and cross sections.
Longitudinal section: The muscle cells are elongated fusiform-shaped. The
nucleus is rod-shaped, centrally located with fine chromatin.
Cross-section: The smooth muscle 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. Myofibrils cannot
be seen in the cytoplasm at the light microscope level.
Emphasis: The feature of the two sections.
CIRCULATORY SYSTEM
The circulatory system consists of cardiovascular system and lymphatic vascular
system. The former includes heart, arteries, veins and capillaries. They, except
capillaries, are usually composed of three tunics, the boundaries between 3 layers are
well clear in medium-sized artery .
1. Medium-Sized Artery
Cross section of medium-sized artery
Number 16
H.E stain
(1) Through the eyes:
It usually has smaller regular tract and thicker wall.
(2) Lower power: showing the tunica intima is thinner and the internal elastic
membrane is prominent; the tunica media is thicker, consists mainly of circularly
arranged smooth muscle cells. The tunica adventitia has the same thickness as the
tunica media, and consists of loose connective tissue. The refractile sheet at the
junction of the tunica media and adventitia is the external elastic membrane. The
boundaries between 3 layers are clear.
(3) Higher power: You can see the tunica intima consists of 3 layers: the
endothelium on inner surface, thin subendothelium and the internal elastic membrane.
The internal elastic membrane has a scalloped appearance and is highly refractile.
Because of contraction of tissue, the nuclei of endothelial cells perches on the internal
elastic membrane.The tunica media consists mainly of 10～40 layers circularly
arranged smooth muscle cells. The refractile undulating tissue in the tunica media is
elastic membrane. There are small blood vessels and nerves within the connective
tissue of tunica adventitia.
Key: internal elastic membrane
2. Large artery
cross sections of common carotid artery
Number 17
H.E stain
(1) Lower power: the large artery is also composed of 3 tunics, the tunic media is
the thickest layer, which consists mainly of 40 ～ 70 layers of elastic
membrane.
(2) Higher power: the tunica intima consists of a lining of endothelial cells which
rest on a layer of connective tissue, the subendothelial layer. This layer is
thicker than that of medium-sized artery. Some smooth muscle cells may be
found in this area. The internal elastic membrane is continuous with those of
tunica media. There is no boundary between them. The tunica media is the
thickest layer of large artery, which has a scalloped appearance and stained in
bright red color. Small amount of smooth muscle fibers, collagenous fibers
and elastic fibers can be found between the elastic membranes. The adventitia
is thinner than tunic media and consists of connective tissue which contains
vasa vasorum and nerve fibers.
3.Small artery, small vein and capillary
The section is taken from human finger skin
Number 23
H.E stain
(1) Through the eyes: dermis and subcutaneous tissue appear pale-staining
(2) Higher power: Small artery has a smaller lumen and a thicker wall. It contains
an endothelial lining, a thin layer of undulating internal elastic membrane. Tunic
media consists of several layers of muscle. The adventitia is connective tissue
which merges with the surrounding tissue. Small vein has a larger lumen and
thinner wall. It contains an endothelial lining and 1～2 layers of scarcely smooth
muscle cells. The connective tissue of adventitia is also continuous with the
surrounding tissue, no clear boundaries between them. Capillary is composed of a
thin endothelium with a basal lamina which are surrounded by a little connective
tissue. The section of capillary has 1-3 endothelial cells in the outermost papillary
layer.
Key: Small artery and small vein
4. Heart
The section of left ventricle
Number 19
H.E stain.
Through the eyes: the endocardium appears rough
(2) Lower power: The endocardium is thin, it is lined by endothelial cells that rest on
a delicate connective tissue, the subendothelial layer. The deeper layer is
subendocardial layer. The myocardium is the thickest layer of heart, consisting of
cardiac muscle fibers, with small amount of connective tissue and a lot of
capillaries, The cardiac muscle fibers travel in different direction, therefore, they
may be cut in longitudinal, cross or oblique directions. The epicardium is a thin
layer of connective tissue. It is surfaced by mesothelium.
(3) Higher power: The free surface of endocardium is lined by a layer of flattened
endothelial cells; the subendothelial layer is made up of delicate connective tissue,
with small amount of smooth muscle fibers. The subendocardial layer is loose
connective tissue, Purkinje fibers are found in this layer. They are thicker than
ordinary cardiac fibers, containing fewer myofilaments located peripherally.
Small blood vessels, adipose cells and nerve fiber can be found within the
connective tissue of epicardium.
Key: subendocardial layer, Purkinje fibers and cardiac fibers
IMMUNE SYSTEM
1. Thymus
These section is taken from human thymus
Number 79
H.E stain.
(1) Lower power: Thymus is surrounded by a layer of dense connective tissue that
penetrates the parenchyma and divides it into incomplete lobules. Each lobule has a
peripheral dark zone known as the cortex and a central light zone called the medulla.
The cortex is mainly composed of large number of closely aggregated thymocytes and
dispersed thymus epithelial reticular cells. Numberous capillaries are among them .
Because the cortex is rich in small lymphocytes, it stains more darkly. The medulla
contains a large number of epithelial reticular cells and few lymphocytes, so it stains
pale. There is continuity between the medulla of adjoining lobules. The medulla
contains thymic corpuscle, which is characteristic of thymus; each lobule contains one
or more in nuber.
(2) Higher power: Thymic corpuscles are concentrically arranged layers of flattened
epithelial reticular cells with crescent-like and clear nuclei in the peripheral zone.
Near the center of thymic corpuscles, the epithelial cells become filled with keratin
and degenerate. In the central zone the epithelial cells are completely keratinized and
acidophilic. Macrophages are also present in this area.
Key: Thymic corpuscle
cortex
medulla
epithelial reticular cell
thymocyte
lobule
2. Lymph node
These section is taken from human lymph node
Number 20
H.E stain.
Through the eyes: Part of the surface of the lymph node is slightly concave ,that is
called
hilus.The peripheral dark zone is known as the cortex , the central light zone is called
the
medulla.
(1) Lower power: Lymph node has a dense connective tissue capsule that sends the
trabeculae into its parenchyma. Each node contains an outer dark blue cortex and a
central light medulla.
The cortex, situated under the capsule, consists of superfacial cortex, paracortex
zone and cortical sinus. Superfacial cortex contains a thin layer of diffuse lymphoid
tissue and lymphoid nodules. When the lymphoid nodules react with antigens, they
increase in size and have lighter-stained center zones called germinal centers. The
germinal centers can be divided into dark zone, the deeper part of germinal
centers,and light zone, the outer part. The outer and peripheral part of germinal center
is called cap, which has the densely packed small lymphocytes. The deeper region of
the cortex is diffuse lymphoid tissue referred as paracortex zone(also called thymus
dependent area),where high endothelial venules or postcapillary can be seen. Cortical
sinuses include the subcapsular sinuses,situated immediately under the capsule, and
intermediate sinuses that run between lymphoid nodules. The sinus is lined by
flattened endothelial cell surrounded by a layer of reticular cell. These irregular spaces
are formed of a network of reticular cells and fibers stained pink, whose meshwork is
populated by lymphocytes and macrophages.
(2) Higher power: The medulla is composed of the medullary cords and medullary
sinuses. Medullary cords are branched cord-like extensions of lymphoid tissue. The
postcapillary, or high endothelial venules can be seen there. Medullary cords are
separated by medullary sinuses, which share the same structure with the cortial
sinuses and communicate with each other. But the medullary sinuses appear wider
than the cortical sinuses, whose meshwork is populated by many macrophages.
Key: cortex
medulla macrophage cortial sinuse lymphoid nodule
paracortex
zone
3. Spleen
These section is taken from human spleen
Number 22
H.E stain
Through the eyes: The white pulp appear as scattered islands of dark blue, whereas
the red pulp is a red loose tissue.
(1) Lower power: The is surrounded by a thick capsule, which consists of dense
connective tissue and a few smooth muscle cells.
Its surface is a layer of mesothelial
cells, the capsule extends into parenchyma. The white pulp consists of periarterial
lymphatic sheath and lymph nodules, The diffuse lymphoid tissue surrounding the
central arteries is referred to as the periarterial lymphatic sheath. The cluster of
lymphocytes surrounding the arteries expands at intervals and the expansions are
referred to as splenic nodules which share the same structure with the lyphoid nodules
in the lymph node.
Germinal centers may be seen in the splenic nodules, with its cap
facing the red pulp. Marginal zone surrounds the periarterial lymphatic sheath and the
lymphoid nodules.
(2) Higher power: The red pulp consists of splenic cords and splenic sinuses. Splenic
cords, separated by irregularly wide splenic sinuses, are branched cord-like extensions
of lymphoid tissue. The spaces between splenic cords are irregular splenic sinuses
containing many blood cells. The elongated rod- shaped endothelial cells line the
splenic sinuses of the spleen. When the sinus is cut in cross section, the cut edges
form a ring that constitutes the spotted-shaped profile of the sinus, the nucleus
protrude to the lumen. All kinds of blood cells are present in the sinuses.
Key:
white pulp
red pulp
splenic sinuses
elongated rod-shaped endothelial cells
splenic cords
splenic nodules
periarterial lymphatic sheath
4. Tonsil
This section is taken from human palatine tonsil
Number 21
H.E stain.
(1) Lower power: Palatine tonsil is lined with a stratified squamous epithelium. Each
tonsil has 10～30 epithelial invaginations that penetrate the parenchyma deeply,
forming crypt. The lamina propria under the stratified squamous epithelium and
surrounding the crypt contains many lymphoid nodules, generally with germinal
centers, and diffuse lymphoid tissue. Under the lymphoid tissue is incomplete dense
connective tissue, the capsule of tonsil.
(2) Higher power: The epithelium of crypt is heavily infiltrated with lymphocytes,
plasmacells,and macrophages and so called lymphoepithelial tissue.
Key: stratified squamous epithelium
crypt
lymphoepithelial tissue
ENDOCRINE SYSTEM
Objectives:
To grasp the morphological features of thyroid gland, adrenal gland, pituitary
gland(hypophysis).
To understand parathyroid gland.
1. Pituitary Gland (Hypophysis)
Material: Pituitary Gland
Number of slice: 53
Staining: HE
Main points to observe:
This is sagittal section through the pituitary. The deeply stained portion is pars distails
and the faintly stained portion is pars nervosa. The 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 cluters, which are contract with extensive sinusoid network. On
the basis of stainbility, it can be divided into 3 types, and cells of same type are
gathered.
Acidophils: They are large in size and stained red. Mostly are polyhedral or
irregular in shape with round nuclei. They can easiy be distinguished from the
remainder by virtue of densely packed red granules in their cytoplasm.
Basophils: They are lesser in number and tend to be a little larger than
acidophils. The basophils are ovoid or polyhedral cells. They have round nuclei. The
cytoplasmic granules are basophilic and colored bluish purple.
Chromophobes: They are the most numerous cells in pars distails. They are
small, round or polygonal cells. Their cytoplasm is stained pale so that the cell
boundaties are not easily visible. Round nuclei are seen in the center of cells.
2. Pars nervosa: It consists primarily of nerve tissue represented by
non-myelinated axons of the hypothalamohypophyseal tract. Distributed among these
nerve fibers are specialized neuroglial cellstermed pituicytes. The nuclei of pituicytes
are round or ovoid in shape. 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 vary in size and are
lined by simple cuboidal epithelium.
Pituitary Gland (Hypophysis)
The pars distalis is the largest part of the hypophysis and contains two main types of
cells, chromphil cells and chromophobes. Numerous capillaries are visible here.
The chromphil cells are subdivided into acidophils and basophils. The
cytoplasm of chromophis 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 in groups.
The pars nervosa 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 present.
The pars intermedia contains colloid –filled cysts or vesicles.
2. Thyroid
Material: Thyroid
Number of slice: 54
Staining: HE
Main points to observe:
The thyroid tissue is composed of follicles, which are irregular,
spherical structures, grouped 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. There are many capillaries 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 follocular epithelial cells or gathered into groups between
follicles.
Parathyroid
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.
3. Adrenal Gland
Material: Adrenal Gland
Number of slice: 55
Staining: HE
Main points to observe:
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. The adrenal glands can be
divided into an outer cortex and inner medulla.
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.
Zona fasciculata: A thicker layer occupies large part of the cortex. It consists
of parallel cords of cells, which are polyhedral with a central nucleus. They are
arranged in straight cords and contain a geat number of lipid droplets in their
cytoplasm. After the lipid contents in cytoplasm are dissolved out during specimen
preparrtion, the fasciculate 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 transition from one zone to another is not distinct. Connective tissue and
abundant capillaries settle among cell cords and cell clusters.
Medulla:
The cells are arranged in cords and clusters. When fixing the adrenal gland in a
fixative,which containschrome 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.
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 sebaccous gland, arrector pelli,sweet
glands.
1. Skin（Finger）
Material: Finger skin
Number of slice: 23
Staining: HE
Main points to observe:
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 lamellated corpuscles.
The epidermis is keratinazed stratified squamous epithelium. It contains no
blood vessels. The epidermal-dermal junction is wavy, due to projection of the
dermis(dermal papillae) into the under surface of the epidermis.
The epidermis can be distinguished into five layers.
1. Stratum basale: This is a single layer of cuboidal or low columnar cells,
which is the deepest layer. The cytoplasm is basophilic and stained blue in color.
2. Stratum spinosum: Above the basal layer is stratum spinosum. This layer
has three to four cells in thickness. The cells are closely packed, polyhedral form.
Between the cells there are fine intercellular clefts separatng 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.
3. Stratum granulosum: This layer is formed of 2~5 layers of flattened cells
filled with dark stained granules. These cells form an irregular layer.
4. Stratum lucidum: Superficial to the stratum granulosum is a layer in which
the cell-outlines are indistinct and the cytoplasm appears acidophilic. This layer is
absent in thinner skin.
5. Stratum corneum: Superficial to the stratum lucidum is the horny 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 is packed with keratin.
The dermis is composed of dense connective tissue. It can be subdivided into:
1. Superficial or papillary layer is connective tissue that constitutes dermal
papillae; these project into the epidemis, which is mounded over and attached to them.
The papillary layer consistsmainly of fine collagenous fibers, reticular fibers and
elastic fibers interweaving with blood vessels. Some papillae may contain special
sensory terminations-tactil corpuscles.
2. The reticular layer consist mainly of bundles of coarse collagenous fibers
running in various directions but mainly parallel to the surface. It also contains
extensive network of blood vessels, nerves and lymphatics.
Below the dermis is the hypodermis. This layer contains connective tissue,
often heavily infiltrated with adipose tissue.
2. Scalp（Human Scalp）
Material: Human Scalp
Number of slice: 23
Staining: HE
Main points to observe:
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 palmer skin, but the
epidermis is especially thinner.
The stratum corneum consists merely of several layers of keratinized cells. The
stratum basale contains more brown pigments. The stratum basale contains more
brown pigments. The dermis is thicker and hairs, arrector pili muscle, sebaccous
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 embedded within its distal deep portion and a hair
follicle. The hair is composed of keratinized cells stained inred, pigment granules are
found in and between the cells. The hair follicle is made up of epithelium and
connective tissue. The inner layer of hair follicle is continuous with the epidermis.
The outer layer of the hair follicle is continuous with the dermis and hair papilla. In
some longitudinal section of the hair, the terminal dilatation called the hair bulb,which
the connective papillary projects in, can be seen.
The arrector pili muscle consists of smooth muscle cells gathered into a
bundle,which bunds to the connective tissue sheath of the hair follicle and connect 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 secretary unit are characterized by a centrally located
nucleus and a pale staining. Vacuolated cytoplasm. The excretory ducts are lined by
stratified squamous epithelium continuous with the epidermis.
Digestive System
Introduce: Digestive system is consist of digestive tract and digestive gland. Digestive
tract is composed of four layers which
made up of mucosa、submucosa、muscularis
and adventitia. We should follow the sequence from the inner surfance of the lumen to
the outer surface of the tube while we observe the organs of digestive tarct. In the
mean time we should concentrate on the morphology of muscosa specifically due to
that mucosa is the most different part of segments of digestive tract. Digestive glands
are parenchymatous organ. The morphological feature of acinus should be
emphasized.
DIGESTIVE TRACT
4. Esophagus
Material: The cross section of esophagus
Number of slice: 28
Staining: HE
Main points to observe:
Mucosa: The epithelium surrounding the lumen is stratified squamous epithelium.
Lamina propria is composed of loose connective tissue. 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.
Muscularis: The inner layer muscularis is circular and the outer layer is longitudinal.
At the lower third part of the esophagus, the muscular consist of only smooth muscle
cells; in the mid portion, a mixture of skeletal and smooth muscle cells; and at the
upper third part of the esophagus, only skeletal muscle.
Adventitia: It consists of loose connective tissue containing blood vessels and nerves.
Stomach
Material: The cross section of gastric fundus
Number of slice: 29
Staining: HE
Main points to observe:
Mucosa: The surface of mucosa is lined by simple columnar epithelium which
composed of mucous secreting cells. The epithelium dips downward forming the
gastric pits, under the epithelium is the lamina propria which contains the gastric
glands open into the base of the gastric pits. Two types of cells in the glands can be
identified:
Chief cells are located in the middle and lower portion of glands. They are column in
shape with deeply stained basophilic cytoplasm and basally located round nuclei. In
some cases, fine secretary granules may be seen in the apical region of the chief cells.
Parietal cells are present mainly in the neck and the body of the glands. They are
rounded or pyramidal cells with one centrally placed spherical nucleus and intensely
acidophilic cytoplasm.
Beneath the base of the glands, the muscularis mucosa consists of an inner ciucular
layer and outer longitudinal layer of smooth muscles.
The submucosa consists of connective tissue containing large blood vessels and
lymph vessels are located.
The muscularis is rather thick and consists of three layers of smooth muscles: outer
longitudinal middle circular, and inner obligue.
The serosa is composed of a thin layer of loose connective tissue and mesothelium.
Jejunum
Material: The longitudinal section of jejunum
Number of slice: 81
Staining: HE
Main points to observe:
Both mucosa and submucosa protrude into the lumen to form plicae circulares
Both epithelium and lamina propria protrude into the lumen of the small intestine to
form finger like structures which are termed as villi
Mucosa : The small intestine villi are projections of the mucous membrane and are
composed of connective tissue covered with simple columnar epithelium. Oval spaces
at the intervals of the epithelium represent the positions of goblet cells with their
content 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 which is called as central lacteal. Surrounding the lacteal
are fine bundles of longitudinal smooth muscle fibers.
The surface of the absorptive cell is specialized to form a definite striated
border( a homogeneous layer which is acidophilic)
The mucous membrane proper is provided with simple tubular glands(intestinal
glands) which are lined throughout by columnar epithelium. At the fundus of each
intestinal glands 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 fibers.
Submucosa: It is composed of loose connective tissue containing blood vessels
and nerve plexus.
Muscularis:
It is composed of two layers of smooth muscle cells. The inner
layer is circular and the outer layer is longitudinal. There are nerve plexus which lies
between them.
Serosa: It is composed of a thin layer of loose connective tissue with a mesothelium.
Duodenum
Material: The cross section of duodenum
Number of slice: 30
Staining: HE
Main points to observe:
The structures of duodenum are similar to those of jejunum except for the following
two characters:
One is that plenty of duodenal glands which are mucous acini locate
in the submucosa. The other is that adventitia is fibrous membrane.
Ileum
Material: The cross section of ileum
Number of slice: 80
Staining: HE
Main points to observe:
The structures of ileum are similar to those of jejunum except for the following
two characters:
One is that there are aggregated lymphatic nodules in the lamina
propria and submucosa. The other is that there are more goblet cells in the epithelium
than that of jejunum. Colon
Material: The cross section of duodenum
Number of slice: 31
Staining: HE
Main points to observe:
The structures of its wall are similar to those of small intestine except for the
following features: One is that it is absence of any intestine villi ;
The other is that
the mucosa is lined by simple columnar epithelium but containing more goblet cells.
Appendix
Material: The transverse section of appendix
Number of slice: 32
Staining: HE
Main points to observe:
The lumen of the appendix is small. The glands are fewer. The lining cells are
simple columnar containing only few goblet cells. The lamina propria has numerous
lymphoid nodules. Lymphoid tissue is highly developed in submucosa. The
muscularis consists of the inner ciucular and outer longitudinal layers. A serosa is
present.
DIGESTIVE GLANDS
5. Sublingual Gland
Material: Sublingual Gland
Number of slice: 87
Staining: HE
Main points to observe:
Sublingual gland is divided into lobes and lobules by connective tissue. Each
lobule is formed of a group of acini and ducts. Sublingual gland is a mixed gland, but
mucous alveolus are the predominate component. Pure serous acini are rare. The
mucous alveoli is larger and more uniform in shape. The intercalated duct is short and
is difficult to be found. Three kinds of alveolus should be observed carefully under
higher magnification.
Serous alveolus：It is composed of serous cells. Serous cells are pyramidal
shape with a round nuclei in the lower part, the cytoplasm are deep stained.
Mucous alveolus：It is composed of mucous cells. Mucous cells are cuboidal
shape with a oval nuclei at the base, the cytoplasm are light stained.
Mixed alveolus：It is composed of both mucous cells and serous cells. The
mucous cells form tubules, but their ends are capped by serous cells which constitute
the serous demilunes.
Submandibular Gland
Material: Submandibular Gland
Number of slice: 27
Staining: HE
Main points to observe:
The submandibular gland is a mixed gland. Both serous and mucous alveoli are
present, although serous alveoli are predominant. The intercalated and striated ducts
can also be identified.
Pancreas
Material: Pancreas
Number of slice: 33
Staining: HE
Main points to observe:
The pancreas consists of lobules separated by loose connective tissue, which
contains blood vessels, lymphatics, nerves and also branches of duct system. The
pancreatic lobules are made up of large number of serous acini. Within the lobules
there are some scattered small irregular masses of paler-stained cells. These are the
pancreatic islets. The cells which line the alveoli are columnar or polyhedral in shape.
The lumen of the acinus is small and is difficult to be seen. The basal cytoplasm of the
acinar cells is strongly basophilic. The apical cytoplasm is acidophilic due to the
present of zymogen granules. In the center of each acinus there may be seen a few
nuclei. These are nuclei of centroacinar cells.
The intercalated ducts are small ducts, lined by three or four low cuboidal cells
in section. 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 cubodial or low
columnar cells. The interlobular ducts occur in the septa between lobules. The lumen
is lined by columnar epithelium in which goblet cells may be found. A thin layer of
connective tissue surrounds the duct.
Pancreas Islets are the endocrine portion of the pancreas. The islets contain four
kinds of cells—A,B,D and PP cells. These cell types can only be distinguished by
special stain such as Mallory-azan and under electron microscope. The islets are rich
in blood supply.
Liver
Material: Liver (Human or swine)
Number of slice: 34
Staining: HE
Main points to observe:
Under low power, we can note that there is a layer of connective tissue
underneath the serosa, forming an external capsule to the organ. The connective tissue
extends into the parenchyma and divides the liver into many roughly hexagonal
shaped units called hepatic lobules. The center of the lobule is marked by the central
vein. Each central vein appears as a single empty space in the section although it is
filled with blood in life.
The connective tissue between the 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 and bile duct (They
are interlobular arteries, interlobular veins and bile ducts)
Under high power, we can note that hepatic lobule is made up of hepatic cord
arranged as anastomosing plates radiating out from the central vein. Hepatocyte is
polygon in shape and its cytoplasm is eosinophilic，sometimes have two nuclei. The
nucleus is large, spherical and vesicular and with a well developed nucleolus.
Between the hepatic cords are the sinusoids. Note that the walls of the sinusoids
are composed solely of endothelial cells. The sinusoids contain macrophages known
as Kupffer cells.
URINARY SYSTEM
1. Slide 39
Kidney
H.E.
The parenchyma of the kidney is divided into two major structures: superficial is
the dark cortex and deep is the light medulla.
The cortex is covered by tough fibrous tissue, the renal capsule. In cortex, the
cortical labyrinth and medullary rays can be distinguished: the medullary rays are
parallel rays of tubules which penetrate the cortex from the base of each medullary
pyramid, while the cortical labyrinth is the granular cortical tissue between the
medullary rays where renal corpuscles and sections of convoluted tubules are located.
The medulla is composed chiefly of collecting elements, Henle's loops, and vasa
recta.
1) Renal corpuscles
In cortical labyrinth, the renal corpuscles are the most distinctive components.
There are two poles in the renal corpuscle, a vascular pole, and a urinary pole. Each
renal corpuscle consists of two structures, a renal capsule and a glomerulus.
① Glomerulus
The glomerulus is a small tuft of capillaries.
② Renal capsule (Bowman`s capsule)
The cup-like Bowman's capsule has an outer parietal layer composed of simple
squamous epithelium. The visceral layer, composed of modified simple squamous
epithelium, is lined by podocytes, which wrap around glomerular capillaries. However,
it is difficult to distinguish between the endothelial cells of the capillaries and the
podocytes. The space between the parietal and visceral layers is termed the Bowman`s
space.
2) Renal tubules
① Proximal tubules
A proximal tubule, which consists of a proximal convoluted tubule (lies in cortex)
and a thick descending limb of the loop of henle, is lined by low columnar epithelial
cells with an acidophilic appearance. There are extensive lateral interdigitations
between neighboring cells, which lend an appearance of having no discrete cell
margins when viewed with a light microscope. The lumen of the tubule is relatively
small and uneven.
The most distinctive characteristic of the proximal tubule is its wide brush border.
The luminal surface of the epithelial cells of this segment of the nephron is covered
with densely packed microvilli forming a border readily visible under the light
microscope giving the brush border cell its name.
② Distal tubules
A distal tubule, which consists of a thick ascending limb of the henle`s loop and
a distal convoluted tubule (lies in cortex), is lined by cuboidal epithelial cells with less
acidophilicity than those of the proximal tubules. Moreover, the cells in distal tubules
are shorter than those of the proximal tubule. The lumen appears larger in distal tubule
than the proximal tubule lumen because of the lack of brush border (microvilli).
③ Thin segments of henle`s loop
The thin segments of henle`s loop, which lie in medulla, are lined by simple
squamous epithelium. The cytoplasm of the epithelial cells are stained pale and the
nuclei bulge into the lumen.
3) Colleting ducts
Collecting ducts, which can be found in medullary rays or medulla, are
composed of cuboidal or columnar cells. The boundaries between the cells are
well-defined and the cytoplasm of the cells are weakly stained or unstained.
4) Macula densa (display specimen)
The macula densa is an area of closely packed specialized cells lining the wall of
the distal tubule at the point of return of the nephron to the vascular pole of its parent
glomerulus. In this juxtaglomeruar region, cells of the distal convoluted tubule usually
become columnar, and their nuclei are closely packed together. The close proximity
and prominence of the nuclei cause this segment of the distal tubule wall to appear
darker in microscopic preparations.
5) Juxtaglomerular cells (display specimen)
The juxtaglomerular cells are specialized smooth muscle cells in the wall of the
afferent arteriole adjacent to the renal corpuscle. The cells are cuboidal in shape, have
prominent nuclei, and cytoplasm is weakly basophilic in the light microscope.
2. Slide 40
Ureter H.E.
There is a star shape to the inner portion of the ureter. The ureter consists of
three layers of tissue.
The inner layer of the ureter is the mucosa, which consists of transitional
epithelium and lamina propria.
The middle layer is the muscularis, which consists of smooth muscle. There is
an inner longitudinal, middle circular and outer longitudinal layer of smooth muscle.
The outer longitudinal layer is not present in the entire ureter.
The outer layer, adventitia, is a supporting layer of fibrous connective
tissue. Adipose tissue is present in the adventitia.
3. Slide 41
Urinary bladder H.E.
The bladder wall has the same tissue layers as the ureter. The layers are:
mucosa, muscularis, and serosa/adventita.
The mucosa is composed of transitional epithelium and lamina propria. The
transitional epithelium has domed shaped cells on the apical surface.
Underneath the mucosa of the bladder is a layer called the muscularis. The
muscularis is smooth muscle. The muscularis of the bladder is subdivided into three
layers of smooth muscle: inner longitudinal, middle circlular, and outer longitudinal.
There is a serosal covering on the upper region of the bladder. On a histology
slide, it is apparent that the serosa is composed of a simple squamous epithelium
overlying a small bit of connective tissue. The serosa is peritoneum. In all other
regions of the bladder, the outer layer of the bladder is adventita. The adventitia is
composed of connective tissue.
Male Reproductive System
1. Slide 42
Testes
H.E.
At the lowest magnification available, a thick fibrous capsule (tunica albuginea)
and the connective tissue septa extending from it can be identified. The tunica
albuginea is covered externally by a serosa. The septa divide the parenchyma of the
testis into lobules. Each lobule contains seminiferous tubules and interstitial tissue.
At high power, following structures would be carefully observed.
1) Seminiferous tubules
The seminiferous tubules are surrounded by 3-4 layers of myoid cells. The
insides of the tubules are lined with seminiferous epithelium, which consists of two
general types of cells: spermatogenic cells and Sertoli cells.
① Spermatogenic cells
Five stages of the development of the spermatogenic cells may be distinguished
from the basal region of the seminiferous tubule to the lumen.
Spermatogonium
The spermatogonia are the first cells of spermatogenesis. They are always in
contact with the basal lamina of the tubule. These round or elliptical cells have a
round nucleus stained darkly.
Primary spermatocyte
The primary spermatocytes lie in the cell layer luminal to the spermatogonia.
They appear larger than spermatogonia and enter immediately the prophase of the first
meiotic division, which is extremely prolonged (about 22 days). A large number of
primary spermatocytes are always visible in cross-sections through seminiferous
tubules. These cells are spherical or ovoid in shape, the nuclei of primary
spermatocytes are round and large, and thread-like chromosomes stained darkly are
visible in these nuclei.
Secondary spermatocyte
The secondary spermatocytes are smaller than primary spermatocytes. They
rapidly enter and complete the second meiotic division and are therefore seldom seen
in histological preparations.
Spermatid
The spermatids lie in the luminal part of the seminiferous epithelium. They are
small and spherical. The chromatin condenses during the maturation of the spermatids
into spermatozoa, and the nucleus becomes smaller and stains darker.
Spermatozoon
The spermatozoa are tadpole-like in shape. A mature human spermatozoon
consists of a head, a neck and a tail.
② Sertoli cells
Sertoli cells are far less numerous than the spermatogenic cells and are evenly
distributed between them. Their shape is highly irregular -- columnar is the best
approximation. Sertoli cells extend from the basal lamina to the luminal surface of the
seminiferous epithelium. Processes of the Sertoli cells extend in between the
spermatogenic cells (cell limits are therefore not clearly visible in the LM). The
nucleus of Sertoli cells is ovoid or angular, large and lightly stained and often contains
a large nucleolus. The long axis of the nucleus is oriented perpendicular to wall of the
tubule. A fold in the nuclear membrane is characteristic for Sertoli cells but not
always visible in the LM
2) Testicular interstitial cells (Leydig cells)
Leydig cells, located in the interstitial tissue between the convoluted
seminiferous tubules, constitute the endocrine component of the testis. They
synthesise and secrete testosterone. Ledig cells occur in clusters, which are variable in
size and richly supplied by capillaries. The cytoplasm is strongly acidophilic and
finely granular. The nucleus is large, round and often located eccentric in the cell.
2. Slide 43
Epididymis
H.E.
It is usually easy to see at low magnification if two types of ducts, the ductuli
efferentes and the ductus epididymidis, are present in your sections. The ductuli
efferentes are lined by a columnar epithelium, which consists of both absorptive and
ciliated cells. The height of the two cells types which form the epithelium of the
ductuli efferentes is variable which gives the lumen a characteristic wavy outline. The
ductus epididymidis are lined by a very tall pseudostratified columnar epithelium.
Most cells of the epithelium, also called principal cells, have long stereocilia.
Stereocilia are non-motile structures, which in the EM resemble large microvilli.
In both types of ducts, the epithelium rests on a distinct basal lamina and is
surrounded by connective tissue containing a thin layer of smooth muscle.
3. Slide 44
Ductus deferens
H.E.
The mucosa of the ductus deferens forms low longitudinal folds. It is lined by a
pseudostratified columnar epithelium, some cells have cilia. The lamina propria is
unusually rich in elastic fibres. The muscularis is well developed (up to 1.5 mm thick)
and consists of a thick circular layer of smooth muscle between thinner inner and
outer longitudinal layers. The adventitia is slightly denser than usual.
4. Slide 45
Prostate
H.E.
The prostate contains tubuloalveolar glands. The glands are embedded into a
fibromuscular stroma, which mainly consists of smooth muscle separated by strands
of connective tissue rich in collagenous and elastic fibres. The muscle forms a dense
mass beneath the fairly thin capsule of the prostrate.
The secretory alveoli of the prostate are very irregularly shaped because of
papillary projections of the mucosa into the lumen of the gland. The epithelium is
cuboidal or columnar. Basal cells are again present, and the epithelium may look
pseudostratified where they are found. The secretory cells are slightly acidophilic and
secretory granules may be visible in the cytoplasm.
A characteristic feature of the prostate is the appearance of prostatic concretions
in the secretory alveoli. They are rounded eosinophilic bodies.
Respiratory system
Objectives:
To grasp the morphological features of lungs and trachea.
Slide 37 Trachea
HE
The cross section of trachea is circular in shape. C-shaped blue colored tissue is tracheal
cartilage. The wall of the trachea and the bronchi system can generally be divided into three layers:
the mucosa, which is the innermost layer, the middle layer—submucosa, which contains glands
and the adventitia, including the cartilage and the connective tissue.
1. Mucosa: It is lined by pseudostratified ciliated columnar epithelium with a lot of goblet
cells and 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 and diffuse lymphatic tissue.
2. Submucosa: It is under the lamina propria. But there is no clear boundary between the
submucosa and lamina propria. The submucosa contains many mixed glands, small blood
vessels and loose connective tissue.
3. Adventitia: It 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 38 Lung
HE
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.
Intrapulmonary bronchus: It is the largest bronchus in lung, possess 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 adventitia changes into several pieces of various sizes.
Bronchiole: It is canal with narrow and irregular folded lumen. Its epithelium is pseudostratified
ciliated columnar epithelium or simple ciliated columnar epithelium. Goblet cells can occasionally
be seen. Outside the lamina propria, there is a circular layer of smooth muscle. Cartilage pieces
decrease or disappear.
Terminal bronchiole: Its caliber is smaller. The wall is thinner, and the lumen is irregular in star
like appearance. Its epithelium is simle ciliated columnar. In the wall, goblet cell, cartilage and
gland disappear, and outside lamina propria a layer of circular smooth muscle can be seen.
Respiratory bronchiole: Its wall is interrupted by numerous alveoli or connected with the
alveolar ducts. Its epithelium is simple cuboidal and contains some smooth muscle and connective
tissue outside the epithelium.
Alveolar duct: It’s surrounded by several alveoli or alveolar sacs. Its wall is discontinuous and
consists of a succession of alveoli, there are knobs between adjacent alveoli( this is the main
difference between alveolar duct and alveolar sac), there is some smooth muscle in the knobs.
Alveolar sac: It is the terminal portion of alveolar duct with several alveoli opening into it,
similar to alveolar duct, but there is no knob between adjacent alveoli.
Alveoli: In the slide, numerous saclike alveoli with irregular forms, varied in size, can be seen.
Between the alveoli there is alveolar septa. The surface of the alveoli is lined with simple
squamous cells( Type I cells) and cuboidal cells( Type II cells).
Alveolar septa: It is between adjacent alveoli. There are some connective tissue, many blood
capillaries and some macrophages in it.
Macrohpage(dust cell): It’s ovoid or irregular in shape. It’s nucleus is round in the center, but
often masked by the granules. Its cytoplasm is red stained and filled with numerous engulfed dark
brown granules,.
Female reproductive system
Objectives:
To grasp the morphological features of ovary and uterus.
To understand the structures of the oviduct and the mammary gland.
Slide 47
Ovary
HE
The ovary is covered by a single layer of flat epithelial cells. Under the epithelium
there is a layer of connective tissue—the tunica albuginea.
Medullary is in the center, containing several blood vessels and a small amount
of loose connective tissue.
Cortex is in the periphery, composed of stroma and follicles. Stroma is composed
of spindle—shaped stromal cells. Scattered throughout the stroma are follicles of
different sizes. Four types of follicles can be distinguished: primordial follicles,
primary follicles, secondary follicles and mature follicle. Primary follicles and
secondary follicles are called as growing follicles.
The primordial follicles are located in the outmost place of cortex and under the
tunica 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 primary follicles contains features as following:
1. Oocyte gets larger, but is still a primary oocyte.
2. follicular cells change to be simple cuboidal or columnar, even two or more
layers.
3. Zona pellucida is the acellular glycoprotein layer surrounding oocyte. It
appears pink.
4. Corona radiata is a single layer of columnar follicular cells. They are arranged
radially surrounding the zona pellucida.
5. Theca folliculi is differentiated by stromal cells surrounding the follicles.
The secondary
follicles contains features as following:
1. Oocyte gets larger, but is still a primary oocyte.
2. follicular cavity appears and is filled with follicular fluid.
3. follicular cells in secondary follicles are called as granulosa cells. Stratum
granulosum refers to the granulosa cells forming the wall of follicle.
4. Cumulus oophorus is located on one side of the follicle and projects into the
cavity with oocyte, zona pellucida and corona radiata.
5. follicular theca differentiates into two layers: theca interna and theca externa.
The theca interna is an inner layer, is rich in blood vessels and cellls. The theca
externa is an outer layer rich in connective tissue cell.
The mature follicles: only exist for a very short moment, hardly seen in the slide.
The atretic follicles: oocyte is disappear, wall of follicle collapses and zona
pellucida shrinks.
Slide 83 Corpus luteum
HE
This slide is from ovary. Corpus luteum are large cell masses or cords. It consists of
the granulosa lutein cells, which are from granulosa cells of the follicle, and the
theca lutein cells, formed from the theca interna cells of the follicle. Granulosa
lutein cells are in the center, predominant, polygonal, large, stained lightly because of
many lipid droplets in cytoplasm. Theca lutein cells are in the periphery, smaller than
granulosa lutein cells, stained deeper of cytoplasm.
Slide 48
Oviduct
HE
The wall of the oviduct is composed of three layers:
1. Mucosa: It forms many plicas making the lumen very narrow and irregular.
It
consists of epithelium and lamina propria. The Epithelium is simple columnar.
The Lamina propria is composed of loose connective tissue.
2. Muscular layer: It is composed of an inner circular layer of smooth muscle
fibers and an outer longitudinal layer of smooth muscle fibers.
3. Adventitia:It is serosa(a thin layer of connective tissue+simple squamous
epithelium).
Slide 47 Uterus (Proliferative Phase)
HE
The wall of the uterus is formed of three layers:
1. Endometrium: It consists of epithelium and lamina propria. The epithelium is
simple columnar. The lamina propria contains long, simple tubular
glands—uterine glands. The uterine glandular cells are similar to the
superficial epithelium. The connective tissue of the lamina propria contains a
large number of spindle-shaped cells.
2. Myometrium: It is of great thickness and is formed of smooth muscle fibers.
3. Perimetrium: It is serosa(a thin layer of connective tissue+simple squamous
epithelium).
Slide 52 Mammary gland(active phase)
HE
Connective stretches into the gland and separate it into many lobules. Each lobule
contains many acini in different functional phases. In some acini, epithelium is high
columnar, there is few secretion in the lumen, in other acini, epithelium is low
columnar or squmous, lumen is full of pink secretion(milk). There are interlobular
ducts between acini, these ducts contain very large lumen and their epithlium is
cuboidal or columnar.