Download Animal Histology BIO 428

Animal Histology
BIO 428
Course Instructor: Dr. Anne Böttger
Animal Histology- Lab Guide
EPITHELIUM
SIMPLE SQUAMOUS EPITHELIUM (Fig. 5.1, 16.6, 16.9, 19.3)
Kidney
Observe the flattened cells lining the lumen of the blood vessels in this slide. Cytoplasm is
often not visible. Note the elongated and flattened nucleus of each cell (stained section of the
cell). The simple squamous epithelium lining the lumen of all blood vessels is specifically
known as the endothelium.
Ovary
Observe resting cells on the outer surface of the ovary. When simple squamous epithelium is found on
the outer surface of an organ it is known as mesothelium.
SIMPLE CUBOIDAL EPITHELIUM (Fig. 5.2, 16.17, 16.20, 16.21, 17.6-17.10)
Kidney
Observe cells forming the numerous tubules in the kidney. Note the rounded nucleus in each cell.
Identify the location of the basement membrane.
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In some of the kidney tubules on this slide, the simple cuboidal epithelial cells have long microvilli
extending from their apical surface (they may also just be found as an accumulation inside the tubules).
These microvilli form what is known as a brush border. Longer microvilli are typically located in the
proximal tubule of the kidney.
Thyroid gland
Observe the simple cuboidal epithelial cells lining the spherical thyroid follicles that occupy most of
the area in this endocrine organ.
SIMPLE COLUMNAR EPITHELIUM (Fig.5.3, 5.4, 14.6, 14,20, 14.21, 14.29, 14.32, 14.33)
Small intestine (14.
In the middle section on this slide, observe the cells covering the finger-like villi. Note the location of
the basement membrane. Identify the striated border composed of short microvilli on the apical
surface of the epithelial cells. Identify goblet cells interposed between some of the other epithelial
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cells. Goblet cells contain mucous secretory material rich in glycoproteins. Study the epithelium in the
other sections of this slide.
Large intestine
Note the absence of villi in this organ. What type of epithelium covers the inner (luminal) surface of
this organ? Are there more or fewer goblet cells in this slide compared to the previous slide? Why?
PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM (Fig. 5.5, 12.6, 12.7, 12.5)
Trachea
Locate the pseudostratified ciliated columnar epithelium on the surface of this specimen. Note the
location of the basement membrane attaching the epithelium to the underlying connective tissue.
Note that nuclei of different cells are seen at different levels even though each cell touches the
basement membrane. Identify goblet cells in the epithelium. Do the goblet cells possess cilia? What is
the difference between microvilli and cilia?
Larynx (use Fig. 12.5)
Identify the two types of epithelium that line different parts of the larynx and vocal cords. Superior to
the vocal cords, identify a stratified squamous epithelium and below the cords find the
pseudostratified ciliated columnar epithelium.
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STRATIFIED SQUAMOUS EPITHELIUM (MOIST, NON-KERATINIZED) (Fig. 5.6, 14.5,14.6)
Esophagus
Locate the epithelium on the luminal surface of the section. Note the location of the basement
membrane. Note the numerous layers of cells in the epithelium and the squamous shape of the cells
directly on the surface.
Esophagus-cardia (stomach) junction
Observe the change in epithelium between the esophagus and the cardiac stomach.
STRATIFIED SQUAMOUS EPITHELIUM (KERATINIZED) (Fig. 5.6, 19.16, 19.17, 19.19,)
Scalp
Note the location of the basement membrane and its irregular contour. Identify the cornified
(keratinized) layer of cells on the surface of the epithelium. The epithelium forms the epidermis of
the skin. Hair follicles, sebaceous glands and sweat glands are present in this section.
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STRATIFIED CUBOIDAL EPITHELIUM (Fig. 5.8, 9.10)
Scalp
Locate the sweat glands in the connective tissue below the surface epithelium. Stratified cuboidal
epithelium is found lining the small ducts of the sweat glands.
TRANSITIONAL EPITHELIUM (Fig. 5.9, 16.27)
Ureter and Urinary Bladder
Locate the epithelium lining the lumen in each of these organs. Note the large dome or cap cells (some
of which are binucleate) in the apical layer of the epithelium. In some areas on each of these slides the
thickness (number of cell layers) of the epithelium may vary. In a full or distended bladder, would the
number of cell layers in the epithelium be greater or less than the number found in an empty bladder?
Or would the appearance of the epithelium in a full bladder change in any other way?
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CONNECTIVE TISSUE
LOOSE IRREGULAR (AREOLAR) CONNECTIVE TISSUE (Fig. 4.5)
Areolar tissue
This is a piece of tissue that has been flattened and spread on a slide. Be able to identify the
collagen fibers that stain pink and the elastic fibers that stain black. The pale nuclei seen
between fibers represent a variety of connective tissue (C.T.) cells, the majority being
fibroblasts. Clear spaces in tissue represent location of amorphous ground substance.
DENSE IRREGULAR CONNECTIVE TISSUE (Fig. 4.6, 4.12, 19.38)
Mammary gland (resting)
This slide contains the skin, which covers the mammary gland. Identify the epithelium of this skin
(what type is it?). Immediately below the epithelium is the layer known as the dermis that is composed
of dense irregular C.T. Note the increased amount of collagen fibers and the decreased number of
cells and space occupied by ground substance as compared to areolar C.T. Note that collagen fibers run
in different directions.
DENSE REGULAR CONNECTIVE TISSUE (Fig. 4.12)
White fibrous tissue
This slide contains a longitudinal and cross-section of a tendon that is composed of dense regular
C.T. Note the very dense arrangement of collagen fibers that tend to run in the same direction. There
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is very little ground substance. The thin dark nuclei compressed between the fibers illustrate the
location of specialized fibroblasts (tendon cells) that produce fibers.
EMBRYONIC CONNECTIVE TISSUE (Fig. 19.35)
Mucous tissue
This is a slide of the umbilical cord that illustrates an embryonic type of C.T. Find the two umbilical
arteries and a single large umbilical vein. The epithelium-lined structure between the arteries is a
portion of the allantois, an excretory structure in the fetus. The best example of mucous C.T. can be
found directly below the epithelial covering of the umbilical cord. Look for stellate shaped fibroblasts
and small bundles of collagen fibers. Note the spaces that would be filled with the amorphous
ground substance. All the specialized C.T. found in the umbilical cord is collectively known as
Wharton’s jelly due to its viscous nature.
ELASTIC CONNECTIVE TISSUE (Fig 8.10, 8.11)
Artery, vein, and nerve
Concentrate your attention on the tissue that forms the wall of the artery and vein. After closing the
iris diaphragm of your microscope and slightly defocusing, you should be able to identify small
bundles of fibers that seem to stand out. Many of these bundles appear wavy (in thick-walled arteries
these are visible without defocussing). These structures represent elastic fibers (black appearance).
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ADIPOSE CONNECTIVE TISSUE (FAT) (Fig. 4.14)
Scalp
Look in the deepest layer (hypodermis) of the scalp (furthest away from the epithelium). Note the
large, rounded, empty fat cells (adipocytes) that form adipose tissue. When living, these cells were
filled with a single large droplet of lipid. Look for a fat cell nucleus that is usually compressed against
the cell membrane.
Adipose tissue
This slide shows fat retaining adipocytes with visible nuclei found in the mammalian mesenteries.
RETICULAR CONNECTIVE TISSUE (Fig. 11.11)
Lymph node
This slide contains a section of a human lymph node. The outer layer surrounding the lymph node,
referred to as the capsule, is constructed of fibrous reticular connective tissue. These fibers also
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continue into the main body of the lymph node where they form the trabeculae of reticular connective
tissue.
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CARTILAGE AND BONE
HYALINE CARTILAGE (Fig. 10.1)
Trachea
Identify the large piece of hyaline cartilage that forms the C-shaped rings in the trachea (in your slide
you will most likely only see a section of these rings). Identify the perichondrium, the layer of dense
connective tissue (that varies between regular and irregular dense connective tissue) that lies on each
side of and surrounds the piece of cartilage. Within the cartilage, identify the chondrocytes (cartilage
cells) within the lacunae. An isogenous group is the name given to a small group of adjacent
chondrocytes. In cartilage the amorphous ground substance is represented by cartilage matrix that lies
between chondrocytes. Note that there are no blood vessels in cartilage.
ELASTIC CARTILAGE (Fig. 10.4)
Elastic cartilage
This slide is stained with a special Verhoeff’s stain that demonstrates elastic fibers. You must
distinguish the cartilage from large areas of fat that lie between pieces of cartilage. The basic structure
of elastic cartilage is similar to that of hyaline cartilage seen in the previous slide. In the matrix, look
for small strands of tissue that stain black or dark red.
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FIBROCARTILAGE (Fig. 10.3)
Fibrocartilage
On this slide, look in the area of transition between the hyaline cartilage and the dense regular
connective tissue. The fibrocartilage that develops in this area can be recognized by lacunae with
chondrocytes, thick parallel bundles of collagen fibers (pink stain) and the absence of a
perichondrium.
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BONE (Fig. 10.9, 10.10)
Bone, human (ground)
This slide demonstrates the appearance of mature compact bone that has been air dried and mounted.
Identify the Haversian systems (osteons) and the centrally located Haversian canals. Identify
lacunae, representing the location of the osteocytes (bone cells) and the canaliculi running between
adjacent lacunae. By “stopping down” the iris diaphragm you may also be able to see layers or
lamellae of bone tissue that look like “growth rings in a tree” within a Haversian system. These layers
represent different periods of growth within the bone.
BONE DEVELOPMENT (ENDOCHONDRAL) (Fig. 10.17–10.21)
Developing cartilage and bone
This is a slide of a developing finger or toe that contains a developing long bone. Use diagram below
for orientation and identification of the structures present:
Identify the epiphysis on each end of the growing bone (where possible) and the future synovial
cavity forming between epiphyses. Note that the epiphyses are composed of hyaline cartilage.
Identify the primary marrow cavity that is surrounded by developing spongy bone (Note – the
spongy bone forms by intramembranous development). Look for osteoblasts on the surface of
pieces of bone (Note – not to be confused with osteoprogenitors or bone-lining cells, which are much
smaller and flatter) and osteocytes in lacunae within the bone tissue. Try to find osteoclasts (identified
by a ruffled border, Fig. 4-9 and 4-10) that are destroying bone tissue. Identify the periosteum.
Identify the area of transition between epiphysis and the marrow cavity. This region contains the
epiphyseal plate, the site where cartilage is destroyed and where new bone formation is occurring.
Moving from epiphysis and the marrow cavity the following zones occur:
1. zone of reserve cartilage
2. zone of cartilage proliferation
3. zone of cartilage maturation or chondrocyte hypertrophy
4. zone of cartilage calcification
5. zone of ossification or bone formation
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MUSCLE AND NERVOUS TISSUE
SMOOTH MUSCLE (Fig. Fig. 6.15, 6.16)
Smooth muscle
This slide contains a cross section of the jejunum. Observe the smooth muscle in the outer layers of
the wall of this organ. Smooth muscle is found in two layers (1) an inner circular layer (closest to the
epithelium) and (2) an outer longitudinal layer. The smooth muscle cell is tapered in shape and the
centrally located nucleus appears elongated when the cell is sectioned longitudinally. When cut in
cross-section, the cell and nucleus appear rounded.
SKELETAL MUSCLE (Fig. 6.2, 6.3, 6.5)
Muscle types
Skeletal muscle is demonstrated in the middle section on this slide. Note the elongated, multinucleated
muscle cells (fibers) with obvious striations. Note that the nuclei are usually found at the periphery of
each cell, close to the cell membrane. Look for skeletal muscle cells cut in cross section.
CARDIAC MUSCLE (Fig. 6.22, 6.23, 8.3)
Intercalated disks
This is a slide of cardiac muscle. Note the elongated shape of the individual cells and the fact that
cells may branch. The nucleus of a cell is generally found in the center of the cell. Identify the
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striations and the darker intercalated discs (very fine lines crossing the striations). The intercalated
discs represent a specialized junctional complex between adjacent cardiac muscle cells.
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NERVOUS TISSUE AND BRAIN
SPINAL CORD AND MULTIPOLAR NEURONS (Fig. 7.23, 20.2)
Spinal cord (concentrate on the cross section)
This slide contains a longitudinal and cross-section of the spinal cord. In the cross-section, distinguish
between the outer white matter and the inner gray matter. Look in the larger ventral horn of the gray
matter to find the large multipolar motor neurons. Neurons can usually be recognized by their large
light-stained nucleus containing a very obvious, dark-staining nucleolus. Look for the processes
(dendrites and an axon) branching from the cell body. Look for neurons in the central region of gray
matter in the longitudinal section. Find the specifically stained slide to observe the Nissl bodies which
are thought to be involved in synthesis of neurotransmitters such as acetyl choline.
CEREBRUM AND CEREBELLUM (Fig. 20.8 and 20.5)
Cerebrum (Fig. 20.8)
The two halves of the cerebrum consist of convoluted grey matter overlaying the innermost medullary
white matter. The internal convolutions may pose a challenge to identify the different cell layers of the
cerebrum.
I.
Plexiform layer = most superficial layer, consisting mainly of axons and dendrites. You
will find sparse nuclei of neuroglia and occasional horizontal cells of Cajal (small,
spindle shaped and oriented parallel to the surface)
II.
Outer granular layer = characterized by a dense population of pyramidal cells (pyramid
shaped cells with a pointed apex oriented towards the cortical apex).
III.
Pyramidal cell layer = contains pyramidal cells of moderate size. Cells of Martinotti
may also be distinguished in silver stained slides.
IV.
Inner granular layer = consists mainly of densely packed stellate cells (cell body forming
the shape of a star, in H&E stained slides these cells will appear like needle shaped cells)
V.
Ganglionic layer = consisting of large pyramidal and fewer numbers of stellate cells.
VI.
Multiform layer = named for its diverse morphological appearances. It always contains
small pyramidal cells and stellate cells.
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In silver (Golgi) or gold stained cerebral slides you will also be able to identify the star-shaped
astrocytes which perform many functions, including biochemical support of endothelial cells which
form the blood-brain barrier, provision of nutrients to the nervous tissue, maintenance of extracellular
ion balance, and a principal role in the repair and scarring process of the brain and spinal cord
following traumatic injuries.
Cerebellum (Fig. 20.5)
The cerebellar cortex forms very easily identifiable convoluted folds or folia. Scan this slide and try to
recognize neurons of various shapes and sizes in different parts of the brain. Many of the smaller
nuclei in the tissue represent the nuclei of neuroglia cells. In the cerebellum, identify the outer
acidophilic molecular layer, the inner basophilic granular layer, and the layer of large Purkinje cells
between the two layers.
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MOTOR END PLATE (Fig. 7.12)
Motor end plate
Locate the synapses on the skeletal muscles, the motor end plates, that may innervate from few to
more than a thousand skeletal muscle fibers. The muscle fibers and the neuron together form a motor
unit.
PERIPHERAL NERVE (Fig. 7.13-7.17)
Artery, vein, and nerve
Locate the blood vessels with the obvious lumens. The cross-section of a nerve should be distinguished
from the blood vessels. The nerve is surrounded by a layer of connective tissue – the perineurium.
Within each nerve, recognize individuals myelinated nerve fibers. Each nerve fiber is composed of an
axon surrounded by a myelin sheath formed by Schwann cells. Most of the nuclei observed are nuclei
of the Schwann cells.
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HISTOPATHOLOGY OF THE NERVOUS SYSTEM
Meningitis
On this slide you will find a section of the brain of a patient suffering from meningitis.
Meningitis is the inflammation of the meninges, which is the outer cover of the brain. Look for
polymorphonuclear leukocytes in inflamed areas of the meninges.
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INTEGUMENTARY AND IMMUNE SYSTEM
INTEGUMENTARY SYSTEM (SKIN)
HUMAN SKIN (Fig. 9.2)
Scalp
Identify the three layers of skin: epidermis, dermis and the underlying loose C.T. of the hypodermis.
Note the cornified stratified squamous epithelium of the epidermis and try to identify the different
layers of the epidermis (not all slides will show all strata):
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1. Stratum corneum =
cornified stratified squamous epithelial cells on
surface (thickest layer)
2. Stratum lucidum
3. Stratum granulosum = easily identified, stained dark
3. Stratum spinosum = cells appear “spiny” due to desmosomes
4. Stratum basale = viewed with high or oil magnification
Identify the keratinocytes and melanocytes in the epirdermis and find slides where you can observe
melanin distribution in the epidermis
Note the dense irregular connective tissue (containing collagen and elastic fibers, the latter visible
only in slides stained with Verhoeff’s stain) in the dermis and the adipose tissue in the hypodermis. Be
able to recognize a hair follicle and the associated sebaceous gland that is usually attached. Also look
for the coiled eccrine sweat glands (stratified cuboidal epithelium) in the deeper parts of the dermis.
Compare skin located at different regions of the body to determine differences in composition of
the dermal layers (Demonstration slides):
1. Axillary skin = increased numbers of hair follicles and presence of apocrine sweat glands
(simple columnar epithelium with cytoplasmic blebbing)
2. Palmar skin = increased layer of stratum corneum, no hair follicles
3. Hairy skin
HISTOPATHOLOGY OF THE SKIN
Malignant melanoma
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This slide contains a section of cancerous melanocyte tissue. Notice the thickened epidermis with
cellular extensions into the underlying dermis. Melanocytes from the epidermis will eventually invade
deeper tissues of the skin, and will be able to spread through the body.
IMMUNE SYSTEM
LYMPH NODE (Fig. 11.9, 11.15)
Reticular tissue
This is a slide of a lymph node. Examine the slide first under low power. Note the capsule of
connective tissue around the node. Strands of connective tissue called trabeculae extend from the
capsule to the middle of the node. On low power, identify the outer portion of the node, the cortex.
The inner (central) portion of the node is the medulla. In the cortex, identify individual lymphatic
nodules with an outer rim of densely packed small lymphocytes surrounding a lighter center of larger,
loosely arranged lymphocytes. This central region is called a germinal center. In the medulla, note
cords of lymphocytes forming lymphatic or medullary cords and spaces between the cords known as
lymphatic or medullary sinuses.
SPLEEN (Fig. 11.18-11.21)
Spleen
The spleen is characterized by having no distinction into cortex and medulla, which distinguishes it
from the lymph node. Examine the slide first under low power. Identify the trabeculae of connective
tissue that extend from the capsule. These trabeculae contain the larger arteries and veins of the spleen.
Identify individual lymphatic or splenic nodules scattered throughout the spleen. Within each nodule,
identify at least one central artery (may not always be in the center). The lymphatic nodules represent
the white pulp of the spleen. Occupying spaces between nodules is the red pulp, consisting of pulp
cords and splenic sinuses that contain different types of blood and phagocytic cells.
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TONSILS
Palatine tonsil (Fig. 11.16)
Find lymphocytes and occasional lymphatic nodules directly below the non-keratinized squamous
epithelium of the oral cavity. Be sure to identify blood vessels.
Pharyngeal tonsil
In this tonsil, note that the lymphocytes and nodules are below a pseudostratified ciliated columnar
epithelium (distinguishing them from the palatine tonsils) that lines the pharynx. When these tonsils
become infected and inflamed they are called adenoids.
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Small intestine
Look at the section on the right (as viewed in the microscope). This is a cross-section of the ileum and
illustrates an aggregation of lymphatic nodules called Peyer’s patches.
THYMUS (Fig. 11.5-11.7)
Thymus
Note that the thymus is surrounded by a capsule of connective tissue and trabeculae of connective
tissue extend from this capsule to separate the thymus into lobules. Within each lobule, identify an
outer cortex (appears darker due to increased concentration of T-lymphocytes) and a centrally located
medulla (appears lighter due to larger and more diffuse lymphocytes). Note that the medulla is
continuous between lobules. Within the medulla of a lobule, identify the thymic or Hassal’s
corpuscles. These structures are only found in the thymus. They contain aggregates of compressed
epithelial cells that may be keratinized or degenerating. Between all of the lymphocytes, look for
stellate shaped epithelial reticular cells with a large, oval, light staining nucleus. These cells form the
structural framework of the thymus.
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DIGESTIVE SYSTEM
LIP (Fig. 13.1)
Lip
Lined by stratified squamous epithelium with desquamating surface cells. The dermis of the outer
part of the lip contains hair follicles associated with sebaceous glands. Both outer and inner lip parts
are separated by the lip core consisting of striated muscles, the orbicularis orbis. The inner lip, or
transitional zone between skin and oral epithelium, is characterized by non-keratinized stratified
squamous epithelium that is thicker than the epithelium of the skin. The oral epithelium contains
mucous secreting labial glands in the dermis.
TOOTH (Fig. 13.4-13.9)
Tooth
The crown of the fully developed tooth is covered with enamel (often not visible in our preparations,
because enamel had to be completely dissolved during tissue preparation), an extremely hard and
translucent material composed of rods or prisms of calcified material cemented together. The
underlying dentine form the bulk of the crown and root and is composed of calcified material similar
to bone. The innermost part of the tooth consists of the pulp cavity, which contains
supportive/connective tissue. The layer of the pulp cavity most closely associated with the dentine
contains odontoblasts, tall columnar cells responsible for dentine formation. The pulp also contains a
rich network of thin-walled capillaries.
Gingival attachment can be found in fully developed and erupted teeth only. The area of gingival
attachment can be devided into attached gingiva and free gingiva, the latter identified by the nonkeratinized stratified squamous epithelium (referred to as gingival epithelium), typical for the oral
cavity. Between the dentine and the free gingivae, where pathogenic organisms can easily breach into
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the gingivae, is called the gingival crevice which extends to the cemento-enamel junction. Extending
to the root of the tooth you will be able to see the cementum.
TONGUE (Fig. 13.10-13.13)
Foliate papillae
This is a section of the tongue showing a type of papilla that projects from the surface. Note the nonkeratinized stratified squamous epithelium. Identify the taste buds on the lateral walls of the papillae.
See demonstration slides of the filiform (slender with conical tips), fungiform (covered by
stratified non-keratinized epithelium, displaying taste buds and having a tissue core of a lamina
propria) and (circum)vallate papillae (with numerous secondary papillae, high concentration of
taste buds in the furrow between papillae, serous von Ebner’s glands at the bottom of the fold).
SALIVARY GLANDS (Fig. 13-15-13.17)
Salivary glands
This slide contains a section of the major salivary glands. Be able to recognize and distinguish the
secretory units (acini = serous; tubules = mucous) and the ducts (simple cuboidal, simple
columnar, or stratified squamous epithelium). Note the specific differences between these glands:
Parotid
contains only serous secretory units composed of cells filled with visible, stained
secretory granules.
Sublingual composed primarily of mucous secretory units containing cells filled with light
staining, fused secretory granules.
Submandibular
a mixed gland containing both serous and mucous secretory units.
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All the following hollow, tubular organs of the digestive system have tissue organized into these
following specific layers (Fig. 14.2):
Mucosa
1. Epithelium lining the lumen
2. Lamina propria of connective tissue below epithelium
3. Muscularis mucosae smooth muscle
Submucosa
dense connective tissue, containing blood, lymph and nerve plexus
Muscularis externa skeletal or smooth muscle divided into 2 or 3 layers, usually containing
myenteric nerve plexus between layers
Serosa
loose connective tissue rich in blood and lymph vessels and adipose tissue
with a surface layer of mesothelium (simple squamous epithelium)
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ESOPHAGUS (Fig. 14.15, 14.6)
Esophagus
Note the non-keratinized stratified squamous epithelium lining the lumen. Identify the mucous
esophageal glands in the submucosa. Recognize the skeletal muscle in the muscularis externa
(from upper 1/3 of esophagus).
Esophagus-cardia junction
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This slide illustrates the junction between the esophagus and the stomach. Note the change in
epithelium from the stratified squamous epithelium of the esophagus to the simple columnar
epithelium of the stomach. Identify the muscularis mucosae and the muscularis externa which are
both composed of smooth muscle in this region of the esophagus and which are continuous between
the esophagus and stomach.
STOMACH (Fig. 14.8-14.14)
Fundic stomach
Use this slide to study the basic histological features of the stomach. Identify the simple columnar
epithelium lining the lumen and note that each cell is a mucous producing cell. Identify the gastric
pits and try to recognize the boundaries of the gastric glands, which extend from the base of the pits
and fill most of the lamina propria. Within the wall of each gland identify the large acidophilic
parietal cells (more numerous in the upper region of the gland) and the smaller chief cells with
obvious secretory granules (more numerous in the deep region of the gland). Recognize the
muscularis mucosae, the submucosa, and the muscularis externa.
Stomach combination
Look at the section on the bottom (when viewed in microscope). This section of the pyloric stomach
(Reminder: There are 4 different stomach regions, cardiac, fundic, body, and pyloric). Note that in
the pyloric stomach the gastric pits are deeper and the gastric glands are composed primarily of
mucous secretory cells.
SMALL INTESTINE (Fig. 14-16-14.28)
Small intestine composite
This slide contains sections of the duodenum, jejunum and ileum. Note these features of each region:
Duodenum (far right when viewed in the scope)
Recognize the finger-like villi lined with simple columnar epithelial cells with a striated border (often
barely visible) and occasional goblet cells. Note the numerous connective tissue cells within a villus.
Identify the crypts of Lieberkuhn (intestinal glands) which open into the space between villi. Note
the Brunner’s glands in the submucosa, a feature characteristic of the duodenum only.
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Jejunum (middle section)
The histological features of the jejunum are similar to those of the duodenum, with a major difference
– there are neither Brunner’s glands nor other characteristic features.
Ileum (far left when viewed through the microscope)
The histological features are again similar to those of the jejunum. One distinguishing feature of the
ileum is the presence of Peyer’s patches (lymphatic nodules) within the lamina propria.
LARGE INTESTINE (COLON) AND APPENDIX (Fig. 14.29-14.32)
Appendix
Note that villi are no longer present. The mucosa surface is flat but intestinal glands project into the
lamina propria. Note the simple columnar epithelium lining the lumen and the increased number of
goblet cells. A characteristic feature of the appendix in the large amount of lymphocytes and
lymphatic nodules that accumulate in the lamina propria.
Large intestine (colon)
The surface of the large intestine lacks villi but long intestinal glands can be seen extending from the
surface into the lamina propria. The epithelium of the large intestine is simple columnar with an
increased number of goblet cells. One characteristic feature of the colon is associated with the outer
layer of longitudinal-running smooth muscle in the muscularis externa. At three locations around the
circumference of the colon, the outer layer of muscle is thickened to form the taeniae coli.
DIGESTIVE GLANDS
LIVER (Fig. 15.1-15.12), GALL BLADDER (Fig. 15.13), AND PANCREAS (Fig. 15. 14, 15.15)
Liver
Under low power, try to distinguish the boundaries of a classical liver lobule. Identify a central vein
in the center of a lobule. Find a portal (canal) and identify the three structures that are normally
present:
1. a branch of the hepatic portal vein
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2. a branch o the hepatic artery
3. a bile duct (lined with simple cuboidal epithelium)
These three structures form what is called a portal triad. Note the cords or laminae of liver cells
(hepatocytes) that run from the periphery of a lobule to the central vein. Identify the small spaces that
represent the liver sinusoids between the rows of hepatocytes. The sinusoids are lined with simple
squamous epithelium (endothelium) and are normally filled with blood, so any type of blood cell may
be seen in the lumen. Large veins that are not part of a triad likely represent sublobular veins that
eventually transport blood to the hepatic vein.
Gall bladder
Identify the three layers in the wall of the gall bladder and the type of tissue within each. The mucosa
contains simple columnar epithelium covering a lamina propria of connective tissue. Below the
mucosa is a muscularis layer composed of smooth muscle. The outermost layer is known as the
perimuscular layer and is composed of connective tissue.
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Pancreas
The pancreas is a gland that has both an exocrine and endocrine function and it is important that you
can distinguish the histological features associated with each function. Under low power, note that the
pancreas is divided into lobules by connective tissue. By concentrating your attention on any lobule,
recognize the more numerous exocrine units of the pancreas, the secretory acini. An acinus is formed
by pyramidal-shaped cells organized around a central lumen. Note stained secretory granules in the
apex of the cells adjacent to the lumen. A characteristic feature of acini in the pancreas is the presence
of centroacinar cells that appear to lie in the center of each acinus. Locate the nuclei of these
centroacinar cells within an acinus. Identify ducts of various sizes within a lobule and in the
surrounding connective tissue. They will be lined with simple cuboidal or simple columnar
epithelium.
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Within any lobule, identify a group of lighter stained cells surrounded by a thin layer of connective
tissue that are not organized in the shape of an acinus. These groups of cells are the islet’s of
Langerhans, the endocrine portion of the pancreas. The cell are usually organized into short cords or
rows that are separated by small blood vessels. Although there are several types of cells present in an
islet that produce the various hormones, only two types are easily distinguished. Alpha cells producing
glucagon generally lie at the periphery of an islet and contain orange stained granules. The lighter
stained cells toward the center of the islet are predominantly beta cells that produce insulin.
HISTOPATHOLOGY OF THE DIGESTIVE TRACT
Appendicitis
The condition on this slide is often caused through invasion of the appendix by bacteria (mostly
Streptococcus sp.) from the intestine. This inflammation starts in the mucosa of the appendix and
consecutively spreads through all layers of the appendix wall. It is characterized by leukocytes within
the lumen of the appendix (under low magnification). Under high magnification you will find two
main inflammatory characteristics. The inflammation often originates within the crypts of
Lieberkuehn and the mucosa is in various stages of destruction through the presence of granular
leukocytes.
Liver cirrhosis
This slide displays a condition of the liver that may be caused either by increased alcoholic
consumption or is a hereditary condition. You will be able to observe an irregularly nodular
appearance of the liver under low magnification. These nodules may be surrounded by septa of
connective tissue, infiltrated by lymphocytes and contain proliferated bile ducts. Due to the
secondary lobular appearance of the affected liver you may find central veins and periportal zones
(hepatic portal triads, containing vein, artery and bile duct) lacking orderly arrangement.
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39
RESPIRATORY SYSTEM
EPIGLOTTIS
Epiglottis
This slide represents the epiglottis of the respiratory tract. It is covered with non-keratinized
stratified squamous epithelium. Identify the region of the dense irregular connective tissue
containing mucous glands. You will also be able to find a section of cartilage in the deeper tissues of
the epiglottis. In contrast to larynx and trachea, this cartilage is elastic cartilage.
LARYNX AND VOCAL CORDS (Fig. 12.5)
Larynx and vocal cords
This slide represents a “coronal” section through the larynx and shows both the vocal cords. Note that
the epithelium covering the actual vocal cords is non-keratinized stratified squamous. Identify the
region where this type of epithelium transforms into pseudostratified ciliated columnar epithelium
(this may be difficult to distinguish). Identify the pieces of hyaline cartilage that form thyroid and
cricoid cartilages in the larynx. Note the occurrence of several lymphatic nodules below the
epithelium in some locations. Some glands may also be present below the epithelium. Identify the
bundles of skeletal muscle fibers that are responsible for the movement of the pieces of cartilage and
the vocal cords.
40
TRACHEA (Fig. 12.6, 12.7)
Trachea
Note the pseudostratified ciliated columnar epithelium with goblet cells that line the lumen of the
trachea. Below the epithelium is a layer of connective tissue (lamina propria) that contains bundles of
collagen fibers and elastic fibers. Mucous glands may be found in the connective tissue as well.
Deep to the connective tissue find the cartilaginous rings of the trachea composed of hyaline
cartilage (you may not see rings, but just a mass of hyaline cartilage). Recognize the characteristic
features of the hyaline cartilage.
LUNG (Fig. 12.8-12.13)
Lung and bronchioles
This is a section of the lung demonstrating several segments of air conducting passageways as well as
the respiratory regions, the alveoli. Identify these structures by their characteristic features:
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(1) small bronchus
lined with pseudostratified
ciliated columnar epithelium
with goblet cells. Small pieces
of hyaline cartilage are still
found in the wall of this
structure. Small bundles of
smooth muscle may be found
between the epithelium and the
cartilage.
(2) bronchiole
the epithelial lining may be
thrown into folds. Epithelium is
pseudostratified ciliated
columnar but goblet cells may
not be as common. Smooth
muscle is more prevalent, but
there is no cartilage in the wall.
(3) terminal bronchiole
the epithelium lining this
structure is usually ciliated
simple columnar without goblet
cells. Smooth muscle is present
but no cartilage.
(4) respiratory bronchiole
these may be difficult to find but
when seen will have ciliated
simple cuboidal epithelium
lining one wall and true alveoli
forming the opposite wall.
(5) alveolus
these structures occupy most of the spaces in the lungs and represent the site where gas exchange
between air and blood occurs. The numerous spaces seen in this section of the lung represent a lumen
or opening of an alveolus. Note the simple squamous (Type I) alveolar cell that line most of each
alveolus. Identify the larger great (Type II) alveolar cells that may be found between some of the
Type I cells. Try to identify the capillaries and other small blood vessels that run in the walls between
adjacent alveoli. Macrophages, called dust cells or alveolar macrophages, may be seen on the surface
of an alveolus or in the connective tissue below the epithelium.
Be able to recognize the branches of the pulmonary artery and the pulmonary vein within the lung.
HISTOPATHOLOGY OF THE RESPIRATORY SYSTEM
All histophatological conditions will be set up as demonstration slides.
Anthracosis (“Smoker’s lung”)
In this condition you will find carbon particles deposited in the interstitial tissues between the alveoli.
These particles are being phagocytized by macrophages, and you may therefore find an increase in
macrophages in these sections of the lung.
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Emphysema
This slide contains a section of the lung of a patient with a condition characterized by the destruction
of alveolar septa. This destruction leads to enlarged air spaces through the thinning and tearing of the
septa between adjacent alveoli. This enlargement leads to a decrease in surface area within the lungs
and therefore decreased gas exchange.
Tuberculosis
Tuberculosis displays different stages of inflammation as it develops in the lung. On this slide you may
therefore find different stages of tuberculosis development. The condition is first characterized by the
presence of monocytes and macrophages within the alveoli. You may also encounter tissue
destruction and scar formation within an affected lung.
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CIRCULATORY SYSTEM, BLOOD, AND HEMATOPOIETIC TISSUE
CIRCULATORY SYSTEM (Fig. 8.1-8.11)
Heart with auricles and ventricles
In the slide of the heart identify the three layers of the heart: epicardium (outermost), myocardium
(middle) and endocardium (innermost). The epicardium is constructed of a simple squamous
mesothelial covering (outermost layer of the epicardium) and a thicker layer of connective tissue.
Embedded in the connective tissue you may be able to identify nerve bundles and adipose cells. The
myocardium consists of two different types of fiber, the cardiac muscle fibers (which make up the
majority of the myocardium) and the occasional Purkinje fibers. The endocardium, or innermost
layer of the heart, consists of two layers visible on this slide: an endothelium constructed of simple
squamous epithelial cells, and a connective tissue layer connecting the endocardium to the
myocardium.
Artery, vein, and nerve
This slide contains a medium-sized artery and vein. Be sure to distinguish the blood vessels from the
nerve and from each other (if possible). Identify the three layers of tissue in the wall of these vessels:
1. Tunica intima (endothelium/ epithelium)
=> separated from the tunica media by a lamina propria (elastic C.T.)
2. Tunica media (smooth muscle)
3. Tunica adventitia/externa (dense irregular connective tissue)
Note that arteries usually have a more prominent tunica media containing elastic fibers (generally of
wavy appearance) and veins have a more prominent tunica adventitia. Look for other smaller blood
vessels, such as arterioles and capillaries, on this slide as well.
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HISTOPATHOLOGY OF THE CIRCULATORY SYSTEM
Myocardial infarct
This slide contains a section of the human heart damaged as a result of obstruction to circulation. Cells
of the myocardium are irreversibly damaged, their nuclei have disintegrated and polymorphonuclear
leukocytes have moved into the spaces between cells. These leukocytes are the first inflammatory
response following a myocardial infarct. Depending on the stage of the myocardial infarct, you might
be able to observe macrophages which have moved into the area of the infarct to clear away necrotic
tissue.
Artherosclerosis
This slide contains a section of a coronary artery with an artherosclerotic lumen. You will be able to
identify the empty lumen of the artery. Surrounding the lumen is the tunica intima (which may be
difficult to distinguish) followed by the smooth muscle of the tunica media containing
artherosclerotic deposits of collagen surrounded by crystalline cholesterol deposits. These deposits
will lead to a narrower lumen of the artery, which inhibits blood flow in these arteries.
HUMAN BLOOD (Fig. 3.1-3.10)
Blood smear, human (be able to identify all of these blood cells and components)
Erythrocytes (red blood cells, RBC’s)
Most numerous structures. Recognize their unique biconcave shape and lack of nucleus.
Thrombocytes (platelets)
Very small stained structures that may be seen in small groups between RBC’s.
Granular leukocytes (white blood cells, WBC’s)
Be able to distinguish between these three types:
Neutrophils
65-75%. Most commonWBC. Cells have a multi-lobed (usually with 2-5 lobes)
nucleus and small pale granules in the cytoplasm. Also called microphages.
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Eosinophils
2-4%. Cells have a bilobed nucleus and numerous large red granules in the cytoplasm.
Contain glycogen and eosin-staining granules. Killing of parasitic worms.
Basophils
0.5-1%. Cells have a nucleus divided into irregular lobes. Identified by presence of
large, dark blue or purple granules in the cytoplasm. Contain heparin/histamine.
Agranular leukocytes
Be able to identify two different types:
Lymphocytes
20-30%. Usually the smallest leukocytes. A lymphocyte can be identified by its large
rounded nucleus surrounded by a very thin area of cytoplasm. Immune reaction against
microorganisms, macromolecules and cancer cells.
Monocytes
3-8%. These are usually the largest leukocytes. These cells can be recognized by their
large C-shaped or folded nucleus surrounded by an obvious layer of cytoplasm.
HISTOPATHOLOGY OF THE BLOOD
Sickle cell anemia
This slide contains blood of a patient suffering from sickle cell anemia. You will be able to identify
erythrocytes of abnormal shape. Some of these erythrocytes will have the characteristic sickle shape
from which this pathological condition received its name, others will have variable abnormal shapes,
such as stars, ovals, etc.
HEMATOPOIETIC (MYELOID) TISSUE (Fig. 3.12-3.16)
Bone marrow
This is a slide produced from a bone marrow biopsy. Note the large number of developing blood cells
in various stages of maturation. Identify the large megakaryocytes that are responsible for forming
platelets. They are the largest cells in the bone marrow and each cell contains a multilobed nucleus.
Note the occasional fat cell. It may be possible to identify the sinusoids, which transport blood from
the marrow (they characteristically look like a cavity filled with small red blood cells). The matured
blood cells enter these sinusoids to gain access to the circulating blood.
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48
URINARY SYSTEM
KIDNEY (Fig. 16.1-16.23)
Kidney
Examine the slide grossly and locate the cortex and the medulla (pyramid). Locate the hilus that
contains the renal artery, renal vein (both not visible on all slides), renal pelvis and the ureter.
Examine the slide under low power and identify the areas and structures mentioned above.
Renal corpuscle
The renal corpuscle is composed of the Bowman’s capsule and the glomerulus (tuft of blood
vessels). Identify the outer wall of the Bowman’s capsule (parietal layer = layer beyond urinary
space) and note that it is lined with simple squamous epithelium. This layer of epithelium is
continuous with a layer of epithelial cells that lie on and partially surround the capillaries of the
glomerulus. This is known as the visceral layer of Bowman’s capsule and is composed of cells
known as podocytes. Be able to distinguish the nucleus of a podocyte from the nucleus of endothelial
cells that form the capillaries of the glomerulus. The space between the parietal and visceral layers of
the Bowman’s capsule is Bowman’s space. Try to locate and identify an afferent arteriole that carries
blood to and an efferent arteriole that carries blood away from the glomerulus. Mesangial cells are
small cells that appear to fill spaces between the capillaries within a glomerulus.
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Proximal convoluted and proximal straight (descending) tubule
You will not be able to differentiate between the convoluted and straight tubules. The proximal tubules
are lined with simple low-columnar or pyramid-shaped epithelial cells with long microvilli on their
apical surface forming a brush border. This feature leads to a very irregular luminal surface and the
lumen may even be obscured. The cytoplasm of these epithelial cells usually stains acidophilic and
appears granular due to the number of mitochondria.
Distal straight (ascending) and distal convoluted tubules
Again, it is not necessary to be able to differentiate between straight and convoluted tubules. This
portion of the tubule system is lined with simple low-cuboidal epithelial cells that do not have an
obvious brush border, therefore the luminal surface is smoother. Each distal straight tubule runs back
towards its glomerulus where it becomes narrower and forms an area where nuclei appear closer
together and more numerous. The modified cells in this area form the macula densa. Large cells
containing secretory granules within the wall of the afferent arteriole at this site represent the
juxtaglomerular (JG) cells that produce renin. The macula densa and JG cells collectively form the
juxtaglomerular apparatus.
Though it is not necessary to distinguish between straight and distal tubules, it is necessary to
distinguish between proximal and distal tubules.
Renal pelvis
Identify the portion of the renal pelvis that is present on this slide. Note that the wall is lined with
transitional epithelium. The renal pelvis narrows to form the ureter.
URETER (Fig. 16.25)
Ureter
The ureter transports urine from the kidney to the urinary bladder. Note the irregularly shaped lumen
due to folding of walls. Identify the transitional epithelium that lines the lumen. Two layers of
smooth muscle are usually present within the walls and may be identified – an inner longitudinal and
outer circular layer.
URINARY BLADDER AND URETHRA (Fig. 16.26-16.27)
Urinary bladder
50
Identify the transitional epithelium that lines the urinary bladder. Realize that the thickness of the
epithelium varies, dependent upon whether the bladder is distended or empty. Directly below the
epithelium is the lamina propria consisting primarily of connective tissue. Within the submucosa,
there are three layers of smooth muscle that may be difficult to distinguish: inner longitudinal, middle
circular, and outer longitudinal.
Female urethra
This slide shows a portion of the short female urethra. The epithelium may vary between transitional
epithelium closest to the urinary bladder and to non-keratinized stratified squamous epithelium
(this epithelium may not be found on every slide) closer to the urethral meatus. Two indistinct layers of
smooth muscle may be found surrounding the lumen.
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ENDOCRINE ORGANS
HYPOPHYSIS (Fig. 17.1-17.5)
Hypophysis
This is a sagittal section of the hypophysis (pituitary gland) and shows three major parts of the gland:
(1) Pars distalis
(2) Pars intermedia (1 and 2 = anterior lobe)
(3) Pars nervosa
A part of the pars tuberalis and infundibulum may also be on your slide. Within the pars distalis,
recognize the cords or clusters of cells surrounded by sinusoidal capillaries. Identify the red-stained
acidophils, the blue-stained basophils, and chromophobes which generally do not stain. Acidophils,
basophils and chromophobes may be found adjacent to each other in the same cluster of cells or may
be grouped together throughout the gland.
Identify the pars intermedia between the pars distalis and the pars nervosa. The cleft or lumen that
may be present between the pars intermedia and pars distalis is likely a remnant of the embryonic
Ratchke’s pouch that forms the pars distalis and pars intermedia. Cells in the pars intermedia are
usually basophils but chromophobes may also be present.
52
Identify the pars nervosa. This lobe is composed of nerve fibers and specialized neuroglial cells,
called pituicytes. Most the nuclei seen in this area are those of the pituicytes. The nerve fibers are
projecting from the hypothalamus and secrete their hormones into capillaries in the pars nervosa.
THYROID AND PARATHYROID (Fig. 17.6-17.13)
Thyroid and parathyroid
This slide contains both the thyroid and parathyroid glands, since the parathyroid glands (4 in
number) are attached to the thyroid. First, examine the thyroid gland that is composed primarily of
epithelial lined thyroid follicles. The spherical follicles are composed of simple cuboidal epithelial
cells that synthesize the thyroid hormone precursors and then secrete them into the lumen of the
follicles. These precursors are stored in the follicles as a substance known as colloid. Colloid may be
stained and visible within a follicle. The size of a follicle varies, dependent upon the amount of colloid
stored and how active the epithelial cells are in removing the precursors for formation of thyroid
hormone. Look for small groups of rounded, light-stained cells in connective tissue between follicles.
These represent parafollicular cells that secrete calcitonin. Try to identify the small capillaries that
surround the follicles.
Now turn your attention to the parathyroid gland and notice the obvious difference in structure. This
organ is composed primarily of compact cords of cuboidal shaped cells with obvious rounded nuclei.
These are the principal or chief cells of the parathyroid that secrete parathyroid hormone (PTH).
Between the cords there are sinusoidal capillaries.
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ADRENAL (SUPRARENAL) GLAND (Fig. 17.14-17.20)
Adrenal gland
Because of the shape of the adrenal (suprarenal) gland and the way it is often positioned on a slide, it
may be difficult to recognize the different regions or zones found in the gland. Note the connective
tissue capsule that surrounds the gland. This capsule may contain variable amounts of fat. Small
arteries may be seen running from the capsule into the cortex of the gland. The adrenal gland is divided
into two major regions – an outer cortex and an inner medulla.
First, examine the cortex and identify the three layers or zones:
(1) zona glomerulosa
15%, this is the outermost zone and is composed of small rounded clusters of columnar or cuboidal
shaped cells. These cells synthesize mineralo-corticoids.
(2) zona fasciculata
65%, this layer is composed of large cuboidal shaped cells organized into long cords, which extend
from the previous zone. These cells normally contain a large amount of lipid that is washed out during
tissue preparation and, therefore, have a vacuolated, spongy appearance. They are called spongiocytes
and synthesize glucocorticoids. Note large sinusoidal capillaries that run between the cords of cells.
(3) zona reticularis
7%, this layer contains branching and anastomosing cords of cells (usually continuous with the 2nd
zone) that generally stain darker than the spongiocytes. Cells in this layer synthesize glucocorticoids
and androgens. Sinusoidal capillaries may be present between these cords of cells also.
Within the middle of the gland is the medulla. This region is composed of large irregularly shaped
cells that are usually found in clusters. The cells usually have a light-stained cytoplasm, an obvious
54
rounded nucleus and are called chromaffin cells. These cells synthesize epinephrine and
norepinephrine. Sinusoidal capillaries and large veins may be found between the clusters of cells.
HISTOPATHOLOGY OF THE ENDOCRINE ORGANS
Goiter
In this slide you will find a section of the thyroid characterized by a lowered production of the thyroid
hormone. Histologically this condition is characterized by the presence of enlarged thyroid lobules.
Within these lobules the follicles may be colloid-free and contain enlarged cells within the simple
cuboidal epithelium surrounding the follicles.
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REPRODUCTIVE ORGANS – FEMALE
OVARY (Fig. 19.3-19.12)
Ovary
This slide contains example of the different types of follicles that may be found in the ovary.
Primordial follicle
These are the most numerous and are found directly under the surface of the ovary. This follicle
contains a large ovum (oocyte) that is surrounded by a single layer of squamous follicle cells.
Primary (unilaminar) follicle
This type of follicle contains the single ovum surrounded by a single layer of cuboidal shaped follicle
cells.
Multilaminar follicle
In these follicles, the ovum is usually surrounded by several layers of cuboidal follicle cells. Identify a
layer of stained material lying between the ovum and the follicle cells. This layer of materials that
surrounds the ovum is known as the zona pellucida and usually stains much darker than the ovum.
Secondary follicle
This type of follicle is distinguished by the presence of an expanding fluid filled space between the
follicle cells. The space is called the antrum of the follicle and it is filled with liquor folliculi.
Mature follicle
This should be the largest type of follicle on the slide. The antrum occupies most of the volume of this
follicle. Identify the ovum and zona pellucida surrounded by several layers of follicle cells within one
wall of the follicle. The region containing the ovum is called the cumulus oophorous. Surrounding the
entire mature follicle is a layer of tissue that seems to separate the follicle from the surrounding
connective tissue. This layer is the theca folliculi and is actually divided into an outer theca externa
and an inner theca interna.
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Atretic follicle
These degenerating follicles are recognized by the presence of irregular masses of material that stain
similar to the zona pellucida. Layers of follicle cells may not be obvious.
Note the connective tissue stroma within the center of the ovary and the large blood vessels.
Corpus luteum
This slide contains a large corpus luteum that forms from a ruptured follicle. The entire follicle is
composed of large light staining cells known as granulosa luteal cells. Cells of the theca folliculi have
also been transformed into theca luteal cells.
FALLOPIAN TUBULES (OVIDUCT) (Fig. 19.13 and 19.14)
Oviduct
The fallopian tubules or oviducts are subdivided into different sections, the infundibulum (closest to
the ovary), the ampulla (site of fertilization), the isthmus and the intramural (connection to the uterus).
Be sure to observe as many different as possible. The different areas of the oviduct will contain
smooth muscle layers and internal ciliated epithelium which can show many folds in the
infundibulum and ampulla.
UTERUS AND CERVIX (Fig. 19.15-19.20)
Uterus (resting)
and
Uterus (estrus)
Compare these two slides showing the uterus in different stages of activity. In both slides, identify the
simple columnar epithelium that lines the lumen and the uterine glands that project into the
connective tissue from the lumen. The region containing the epithelium and glands is known as the
endometrium. Note the increased number and size of the glands in the active (estrus) uterus. Also note
the increased number of blood vessels around the glands in the uterus in estrus. Identify the
myometrium composed of layers of smooth muscle.
Uterus (menstrual)
In this slide you will be able to see the endometrium of the uterus in the early stage of menstruation.
The result is the superficial degeneration of the superficial layers of the endometrium.
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Cervix uteri
The cervix is covered with a layer of stratified squamous epithelium in the area of the vagina, while
it has simple columnar epithelium covering the endocervical canal (Remember: The cervix
protrudes into the upper vagina and contains the endocervical canal, so you would expect the transition
of epithelium from stratified squamous to simple columnar).
See demonstration slides of the placenta.
HISTOPATHOLOGY OF THE FEMALE REPRODUCTIVE ORGANS
Endometriosis
Endometriosis describes the growth of endometrial tissue outside the uterine cavity. This indicates that
you will find typical endometrial constituents, such as endometrial glands and small cells within the
abdominal wall. The glands may become encysted when in the abdominal wall.
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REPRODUCTIVE ORGANS – MALE
TESTIS (Fig. 18.2-18.9)
Testis
In this slide of the testis, recognize the different layers of cells undergoing spermatogenesis within
each section of a seminiferous tubule. Note the spermatogonia adjacent to the basement membrane
of each tubule. Also identify the maturing spermatozoa (sperm) toward the lumen of each tubule.
Cells between the spermatogonia and spermatozoa are either spermatocytes or spermatids. Try to
identify small groups of interstitial cells (of Leydig) in the connective tissue between seminiferous
tubules. What is the difference between spermatogenesis and spermiogenesis, both of which are
occurring on this slide.
EPIDIDYMIS (Fig. 18.12)
Epididymis
Realize all of these structures seen in this slide are actually sections of the single, long, tubular duct of
the epididymis. The lumen of the duct is normally lined with pseudostratified columnar epithelium.
On the apical surface of each columnar cell, try to identify the long microvilli, which are called
stereocilia. What is the difference between cilia and stereocilia. Note all of the spermatozoa within the
lumen of the duct of the epididymis.
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ACCESSORY GLANDULAR STRUCTURES (Fig. 18.14-18.18)
Seminal vesicle
Seminal vesicles are composed of convoluted glandular diverticula lined with pseudostratified
columnar epithelium. Epithelial cells may often contain brown lipofuscin granules. The prominent
outer, muscular wall of the seminal vesicles is arranged into an inner circular and an outer
longitudinal smooth muscle layer.
Prostate gland
The low power view of the prostate gland shows the central urethra (identified by transitional
epithelium) surrounded by the connective tissue of the urethral crest. The glandular area of the
prostate is subdivided into superficial lobes separated by fibrous septae of connective tissue. The
epithelium of the convolutions of the peripheral zone is typically tall columnar with prominent
round, basal nuclei. The prostate of older individuals may contain increased accumulations of
hardened, calcified secretion, the corpora amylacea.
PENIS (Fig. 18.19)
Penis
When looking at the slide of the penis observe if first with the help of the dissecting microscope to
identify the large bodies within the penis: the corpus spongiosum containing the urethra and the
corpus cavernosum, which is a cylinder of erectile tissue above the corpus spongiosum (Remember:
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There are always paired corpora cavernosa in the penis, but this slide shows only one). Surrounding the
corpus cavernosum is fibroelastic connective tissue commonly known as the tunica albuginea. You
may be able to see the hypodermis surrounding the penis. Be sure to observe the transitional
epithelium of the urethra under higher power. In the corpus cavernosum you will be able to observe
the vascular sinuses and helicine arteries under high power.
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SENSE ORGANS
EYE (Fig. 21.3-21.18)
Eye development
This slide shows a horizontal section through the eye. The front of the eye is covered by the cornea, a
tough outer layer protecting the eye. Behind the cornea is a seemingly empty space, which is fluidfilled in the living eye. You will be able to identify the iris (composed of the anterior border layer,
the iris stroma, a layer of smooth muscle and the posterior pigmented epithelium) coming down
from top and bottom of the eye, close to the lens (composed of a lens capsule, a subcapsular epithelium
and lens fibers). The opening formed by the iris is the pupil. The inner space of the eye is filled with
vitreous body and lined by the retina. At the back of the eye you might be able to identify the location
where the optic nerve attaches to the eye.
Ciliary Body (Fig. 21.11)
The ciliary body is an inward extension of the choroid at the level of the lens. Ciliary processes are
short extensions of the ciliary body towards the lens. A small amount of loose connective tissue similar
to that of the choroid is located between smooth muscle cells that form the bulk of the ciliary body,
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the ciliary muscle. The inner surface of the ciliary body and its processes are lined by two layers of
cuboidal cells which belong to the retina - the ciliary epithelium formed by the pars ciliaris retinae.
The outer cell layer is pigmented and photosensitive, whereas the inner cell layer, i.e. the layer that
faces the posterior chamber of the eye, is non-pigmented. The ciliary processes contain a dense
network of capillaries. The cells of the inner layer of the ciliary epithelium generate the aqueous
humor of the eye. Fibers, which consist of fibrillin, extend from the ciliary processes towards the lens
and form the suspensory ligament of the lens (also called zonule fibers). Two of the bundles of the
ciliary muscles attach to the sclera and stretch the ciliary body when they contract, thereby regulating
the tension of the zonule fibres. The reduced tension will result in a thickening of the lens which
focuses the lens.
Cornea (Fig. 21.15)
The cornea of the eye covers the anterior one-sixth of the eye. The outside of the cornea is lined by
non-keratinized stratified squamous epithelium that is four to six cell layers thick. This epithelium
is very different from the keratinized stratified squamous epithelia you have observed in the skin. It is
much thinner and has a very even basement membrane, which is also known as Bowman’s
membrane. The bulk of the cornea is constructed of the stroma or substantia propria, consisting of
dense regular connective tissue, followed by a thick elastic basement membrane also known as
Descemet’s membrane. The inner surface of the cornea is lined by endothelial cells characterized by
dark-stained, flattened nuclei.
Lens (Fig. 21.14)
The lens consists of a lens capsule, the subcapsular epithelium and lens fibers. It does not contain
blood vessels or nerves. The lens capsule is generated by the cells of the subcapsular epithelium and
corresponds to a thick, elastic basal lamina. Cells of the subcapsular epithelium (or anterior lens cells)
are mitotically active. In adult individuals they only cover the anterior "hemisphere" of the lens. As
they divide, cells gradually move towards the equator of the lens where they transform into lens fibers.
The mature lens fibers are hexagonal and up to 12 mm long.
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Retina (Fig. 21.5-21.7)
The retina of the eye contains the photoreceptors and is constructed of numerous (10) layers. The
innermost layer, which forms the barrier between the vitreous body and the retina is a thin innerlimiting membrane. Following this membrane you will be able to identify a thicker layer of optic
nerve fibers followed by a ganglion cell layer which is characterized by large, round, dark-stained
nuclei. The inner plexiform layer is clear in appearance and contains integrating neurons. Following
this you will find the inner nuclear layer characterized by four to six rows of cells with dark-stained
round or oval nuclei. The almost featureless and colorless layer following the inner nuclear layer is the
outer plexiform layer which forms synaptic connections to the inner nuclear layer. The layer
containing densely packed, dark-stained nuclei is described as the outer nuclear layer containing the
cell bodies of the rods and cones (cell bodies of the photoreceptors). Following this layer is an outer
limiting membrane followed by the photoreceptor layer made of the processes of the rods and
cones. The outer layer of the retina is constructed of a single layer of pigmented epithelial cells, with
large, oval nuclei and lies close to the vascular and pigmented middle layer of the eye, the choroid.
EAR (Fig. 21.19-21.27)
Cochlea
This slide contains a section through the cochlea, which is the auditory sense organ located in the inner
ear. The cochlea has a construction similar to the conical snail shell, where each turn of the spiral is
separated from the next. Each turn of the spiral can be separated into different canals, the largest being
the scala vestibuli. The middle chamber is the scala media, which is approximately triangular in cross
section, and is the smallest of all the canals. This canal is covered on one side by the stria vascularis,
a stratified squamous epithelium, which regulates the ionic content of the endolymph inside the scala
media. Underlying this layer of epithelial cells is the spiral ligament. The other side of the canal is
covered by a thickened mass of tissue known as the spiral limbus. The scala media and scala
vestibuli are separated by the vestibular or Reissner’s membrane, constructed of thin fibrous
materials, lined by simple squamous epithelium on either side. The lower canal is the scala tympani.
It is separated from the scala media by a membrane known as the basilar membrane. The separating
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membrane between the scala tympani and the scala media is thinner than the one separating the scala
media from the scala vestibuli. In the separating area you will also find a large ganglion characterized
by a large collection of solid pink, round cells. You will also find bundles of afferent nerve fibers
located between the scala tympani and the scala media.
SENSORY RECEPTORS
Meissner’s corpuscle (Fig. 7.31)
This slide contains a section of the skin. You will be able to find the oval Meissner’s corpuscles in the
dermal papillae located immediately below the epidermis. These corpuscles detect light touch. They
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are composed of a thin capsule constructed of connective tissue and filled with transversely arranged,
oval cells (you can identify the dark stained nuclei) likely to represent specialized Schwann cells.
Pacinian corpuscle (Fig. 7.32)
This slide also contains a section of the skin, but on this occasion you will have to focus on the deeper
regions of the skin, such as the deep dermis to find these receptors. Pacinian corpuscles are onion
shaped (oval) and are used to detect deep touch. These receptors are constructed of a thin connective
tissue capsule enclosing many lamellae of flattened cells, possibly constituting specialized Schwann
cells.
Motor end plate (Fig.7.12)
The motor end plate appears in a whole mount as a flat, oval area. Approaching the skeletal muscle a
motor axon loses its myelin sheath, ramifying into several branches and ending in motor end plates
forming a neuromuscular junction, where neurotransmitters are released.
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