Histology Laboratory
اين صفحه براي يادگيري بهتر دانشجوياني كه واحد آزمايشگاه بافت شناسي پايه را دارند تهيه شده است.
بديهي است كه اشكال اين سايت صرفا جنبه كمك آموزشي دارند و پرينت آنها نمي تواند بعنوان گزارش كار آزمايشگاه ارائه شود.
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CARTILAGE,
DENSE FIBROUS CONNECTIVE TISSUE (TENDON)
LOOSE
FIBROUS CONNECTIVE TISSUE
TONGUE,
TOOTH, TOOTH DEVELOPMENT
PITUITARY
GLAND (HYPOPHYSIS), PINEAL GLAND (EPIPHYSIS)
THYROID
GLAND, PARATHYROID LAND, ADRENAL GLAND
MALE
REPRODUCTIVE SYSTEM TESTIS
Epithelium
General
You can see structures best when the slides, eyepieces and lenses are clean. Always carry microscope in upright position because the oculars or condenser may fall out. Be sure to look at other people’s slides since some of the slides are in pretty poor shape or do not show critical structures. If you can’t find the structure in yours or other’s slides, get another out of the cabinet. In this first lab, you do not have to know where these cells come from or what the tissues are. You are responsible for learning the types of epithelial cells or structures.
The goal in the first slides is to be able to tell the difference between the different types of epithelium; whether they are keratinized, stratified, and whether they are ciliated or contain microvilli.
. Simple squamous epithelium (isolated).
2. Stratified squamous epithelium non-keratinized from the vagina. The portion lining the lumen contains the epithelium. Under high power, see the types of cells that make up this lining. The innermost layers of cells are cuboidal, but towards the surface they become squamous. Remember that in stratified epithelia, the outer layer determines the classification of the epithelium. Below the lining of the epithelial cells lies the region of connective tissue.
3. Stratified squamous from the esophagus.
4. Simple cuboidal epithelium surrounding thyroid follicles.
5. Simple cuboidal to simple columnar in kidney
of monkey or Rabbit Kidney
slide. Hold the slide up and look at it
grossly. You see a large Y-shaped
region. This is the urinary space of the
minor calyx. Thin tubules enter/drain
into this space, having radiated through the light pink medulla region from the
darker red, cortex region.
Microscopically, the medulla contains tubules with cuboidal
(cube-shaped, with a squarish profile) or short columnar (taller than it is
wide) epithelium. You will also find
some very narrow tubules with squamous (flattened cells) epithelial walls. The cortex has glomeruli with squamous
epithelium, and tubules with cuboidal epithelium.
6. Simple columnar epithelium of the pyloric stomach. This is the layer closest to the lumen. See also number 14 on this sheet.
7. Pseudostratified columnar ciliated epithelium in the respiratory passages (trachea). Note that this is a slice of a tube. Look at the inner lining to find the epithelial cells. These are pseudo-stratified (falsely layered) because the nuclei are at different levels and the cells are of different heights, but all cells sit on the basement membrane (which is not obvious in this slide). Thus, there is only a single layer of different-sized cells. These epithelial cells are ciliated, and this differs from the brush border of the gut epithelial cells. Make sure you can tell the difference between cilia and microvilli of the brush border. You will also see goblet cells here. These are the flask-shaped cells sitting on the outer 2/3 of the epithelium. The base of the goblet cell also sits on the basement membrane. What is the purpose of the cilia?
8. Transitional epithelium of the urinary bladder. The bladder has a folded lumen (central space). This lumen is lined by transitional epithelium. Note the layers of epithelial cells. The outer layer of transitional epithelial cells (sometimes called umbrella cells) has an outer lining of dark red material. This dark lining is formed by the invagination of the membranes to accommodate stretching of the cell when the lumen is expanded (when the bladder fills).
9. Stratified squamous epithelium keratinized (from primate palm). Compare this with the stratified squamous epithelium of the vagina.
10. Mouse tongue or rabbit tongue. The upper surface has papillae, which are projections of the stratified squamous epithelium which create friction. The papillae are keratinized. This means that the epithelial cells have died and produced a non-cellular layer of keratin on the surface. Keratinized epithelium lines the body surface for protection. For now note the intact cells under the keratinized layer. In the mouse tounge, note the spiky appearance. These spikes are false intercellular bridges. These do not connect the cytoplasm of adjacent cells, but are really sites of cell membrane (junctions, desmosomes) that connect the adjacent epithelial cells. When the material was prepared, there was shrinkage, and the cytoplasm pulled away from the next cell, leaving only the strong desmosomal attachment, creating this appearance. “Stratified squamous” means that the uppermost cells are squamous in appearance, and stratified means there is more than one layer of cells.
11. Mitochondria from turtle liver. This is a special preparation designed to stain mitochondria. Look under high power to see the little dark dots which are the mitochondria. It may be better to look towards the middle of the specimen rather than the periphery. Try not to confuse these with nuclei and nucleoli.
12. Golgi Apparatus. In the electron microscope, this is seen as a system of parallel membranes arranged around the nucleus. On this slide, it is seen as black splotches in the cytoplasm of large round nerve cells. These nerve cells gave a large, light nucleus with a dark dot (nucleolus).
13. Scalp, The skin consists of stratified squamous epithelium, keratinized. The basal layer is cuboidal, but becomes squamous in the upper layers. The cells die and form keratin, which are layers of protein that slough off regularly. Identify the hair follicles, sebaceous (oil) glands, sweat glands and smooth muscles making up the arrector pili muscle.
14. Gut epithelium / Small intestine (duodenum) simple columnar cells. First orient yourself under low magnification. The finger-like processes (villi) are cut in different planes, producing different shapes. Under high magnification, observe that the lining of these villi contains a simple columnar epithelium with a striated or brush border (see the electron micrograph). The brush border can be seen as a thin amorphous pink layer at the top of the epithelial cells. In most preparations some cells are different from the simple columnar epithelium. These appear as dark shadows or clear spots on the luminal surface of the epithelium as you focus up and down. These are the goblet cells, which are unicellular mucous secreting cells. Can you tell the active from the inactive cells? Think about euchromatic versus heterochromatic nuclei.
15. Parotid gland. Identify the secreting portion and the ducts. Most of the gland is make up of serous secreting alveoli (sacs of cells), which have characteristic round, rather light, central nuclei and pink cytoplasm. The ducts look like necklaces, with the cells being cuboidal, stratified cuboidal, to columnar. Examine the large ducts in the spaces between lobules – some of these are stratified cuboidal.
Connective
Tissue and Bone
17. Loose CT. Loose CT fills the space just below the epithelial surface on the tongue and scalp. It has relatively few cells a s evidenced by the few nuclei seen in this region. Fibers (made by the cells) and fluid make up much of the CT. It consists of irregularly arranged noncellular material – thin fibers of collagen, and thin spider-web like filaments of elastic- and several types of cells. The cells normally present are fibroblasts (which make the fibers), adipose (fat) cells, white blood cells and macrophages. See the fibers running in different directions.
18. Human Skin – dense irregular CT. The epithelial layer (what kind is it?) overlies the dermis, which consists mainly of dense irregular CT. Note the bundles of collagen arranged in different directions (irregular). Where are the nuclei in this CT? These nuclei usually belong to fibroblast cells. The dermis consists of a thin upper layer of loose CT and a thick lower layer of dense irregular CT. Compare these two regions and be sure you can differentiate them.
19. Reticular CT . This is a special stain preparation that makes the reticular fibers black. To see this, use the 40X objective. Not the thin black branching fibers.
20. Tendon – dense regular CT. In this longitudinal section, many bundles of parallel oriented collagen fibers are interspersed with rows of fibroblast cells (you may be able to see their nuclei). Blood vessels and some fat cells are also present in here. Loose CT usually surrounds the blood vessels.
21. Hyaline cartilage. Identify the chondrocytes, lacunae, cartilage matrix and perichondrium. The cartilage is filled with lacunae (spaces) which contain cartilage cells (chondrocytes). The chondrocyte borders are not well defined, but you can tell the number of cells per lacuna by counting the nuclei. The thing that looks like a well-defined cell border is really the capsule around the lacuna. The matrix is the non-cellular pink stuff that fills the spaces between cells. Dense irregular CT surrounds the cartilage as the perichondrium.
22. Elastic cartilage. Identify the chondrocytes, elastic fibers and perichondrium. The components of elastic cartilage are similar to hyaline cartilage, but there are many purple elastic fibers between lacunae. Elastic tissue gives the cartilage much flexibility.
23. Fibrocartilage. Note that this resembles dense CT with lots of bundles of collagen and chondrocytes in lacunae interspersed between the collagen.
24. Adipose tissue. Adipocytes appear characteristically empty. In fact, in preparation, the lipids were dissolved – they are empty. Where the large white space is, a lipid droplet was. Note the position of the nucleus and see if you can find any blood capillaries nearby.
25. Ground bone. Identify the Haversian systems (osteons), Volkmann’s canals, lacunae, Haversian canals, concentric lamellae, interstitial lamellae, canaliculi and osteocytes.
26. Decalcified bone c.s. The slide is a cross section of a bone surrounded by muscle; the large central area makes up the bone marrow cavity. Between the marrow and muscle is the bone itself, and you should id the central (Haversian) canals with the surrounding lamellae (see with the diaphragm closed down), and lacunae with osteocytes within. Note the periosteum.
27. Developing cartilage bone. This is cartilage being replaced by bone. Identify hypertrophied chondrocytes, chondrocytes in lacunae, calcifying cartilage, bone spicules, periosteal bone, periosteum and marrow. With higher magnification, identify osteocytes and osteoblasts. Look for osteoclasts, which are large multinucleated macrophages that consume bone matrix during development or remodeling of adult bone.
28. Developing membrane bone. Membrane bone develops to form the flat bones of the skull. The section you have is a slide through he head of an embryo, and you can see the eyes on either side, and a part of the brain, Membrane bones are those structures looking like hyaline cartilage, but a bit darker in color. The closely packed large nuclei (osteoblasts, which are making the bone) on the surface of this bone distinguishes it from hyaline cartilage. Note the pink bony spicules in which the osteocytes are embedded in their lacunae. Identify the osteocytes, bone, osteoblasts and osteoclasts.
29. Areolar tissue. Note the large number and variety of the cells present. Collagen fibers, which make up the bulk of the tissue, may be too lightly stained to be seen directly, but the sinuous pattern seen in the background is caused by light refraction by bundles collagen fibers. The fine, darkly lines are elastic fibers.
30. Epiphyseal plate. There is only one “good” slide at the front of the room. In this slide, I want you to note the second ossification center forming at the head (epiphysis) of the long bone. In this slide there are actually two secondary centers. The cartilage in between is the Epiphyseal plate, and is the lengthening part of the bone. In older developing bones, spongy bone occurs on both sides. One is associated with the marrow cavity, the other the spongy bone of the head of the bone. Remember the elongating zones occur only next to the primary center of ossification.
31. More long bone development. Endochondral Ossification. Remember that during bone development, there is a hyaline template in the embryo. This slide is an example of ossifying bone. Make sure you can identify the following features in this slide: Zone of reserve cartilage, zone of proliferating hyaline cartilage, zone of hypertrophying cells and their associate lacunae (hypertrophic zone), zone of calcifying cartilage, zone of erosion and ossification, periosteal bone (bone collar), osteocytes, chondrocytes, bone spicules.
32. Kitten femur. Some beginning remodeling is visible. Osteoclasts (but not their nuclei) should be visible.
33. Mouse tail cs. This slide is for practice. It will come in handy later in the course when you become more familiar with all the tissues. Identify as many tissue types as possible. Bone, muscle and nerve are present.
Connective Tissue and Bone
MUSCLE
NOTE: Smooth muscles may appear like dense CT (either regular or irregular). You can tell the difference by examining the nuclei. In smooth muscle, nuclei are fairly numerous and randomly scattered throughout the fibers. In dense CT, since the fibers are extracellular (collagen), there ar no nuclei within them. The nucli are more sporadic and belong to fibroblasts that make the collagen. Also, smooth muscle fibers are distinct units, while collagen fibers may be fused into large bundles. Compare connective tissue and smooth muscle on this slide. The CT lies above the muscle layers. Also, you can find CT in other slides in your box.
36. Skeletal muscle (isolated, rather thick section). These fibers were teased apart during preparation. They show the peripheral position of the nuclei pretty well because of the three dimensional image (provided you are using both oculars!). Notice striations. However, you probably will not be able to view the striations very well at high power because of the thick slice.
37. Muscle composite. Great slide. First view the slide grossly. Then, under the microscope, see if you can pick out the different kinds of muscles on this slide. You may want to come back to this slide later after you familiarize yourself with the features of skeletal and cardiac muscle.
10. Skeletal muscle of the tongue. Find the skeletal muscle in this slide. In this stain, you should be able to see the streaking of the myofibrils that run parallel to the fiber itself. The skeletal muscle makes up most of the body of the tongue. Observe the different orientations of the fibers and then flap your tongue wildly about for full appreciation.
Slide at demonstration scope. I’ll have an oil emersion objective on skeletal muscle to show the striations at high power. Note the thick dark pink A-band alternating with the light I-band, with the thin Z-line in the center of it. The H-band is a slightly lighter band in the center of the A-band.
38. Motor end plate. At 100x magnification (10x objective), look for regions where you can see thread-like strands over the muscle fibers. They should be separating and spreading out (arboring) over different fibers as they terminate. Examine this region at higher magnification, and you will see patches of black dots on the fiber surface. This is the myonural junction (motor end plate on muscle, terminal butoun on nerve) where the nerve activates the muscle to contract.
39. Monkey cardiac muscle. Look for striations, intercalated disks (dark bars across the fibers in longitudinally sectioned fibers), central location of nuclei within the fiber, and fibers that branch. Compare cardiac fibers to smooth muscle fibers which lie in the walls of large blood vessels in the heart.
40. Ventricular myocardium. Try your luck with this one – it’s a doosey. Look at this with high magnification or oil immersion. Each fiber is filled with myofibrils (light grayish) and mitochondria (darker purplish). These mitochondria are arranged in rows, which are prominent in longitudinal sections of the fibers. In these, you see a dark row of mitochondria lying between layers of myofibrils. In cross section, you can see individual mitochondria as dark round structures lying between the lighter myofibrils. Larger ovoid or spherical nuclei can be either pink or pu4rple, and are in the center of the fibers. Note the intercalated disks in longitudinal sections of the fibers. Capillaries and larger blood vessels run between the fibers.
41. Perkinje fibers. Another tough one because the slides we have are so crappy. These are modified cardiac muscle fibers that come down the interventricular septum as the “bundle of His”, and then run along the endocardial (luminal) lining of the ventricles to activate the normal cardiac muscle fibers. Note that these fibers have a reduced content of myofibrils and are much larger than the normal cardiomyocytes.
42. Spinal cord smear. This is not a slice of the cord, but a smear of cells from the spinal cord. Find the multipolar neurons and note th nucleus within each neuron. Look at the cytoplasm under high magnification. You will see fine fibrils oriented toward the processes; these are neurofibrils (mainly intermediate filaments). A granular densely staining area is the Nissl body, and a region that contains very little Nissl substances is the axon, while the other processes are the dendrites.
43. Left Empty on purpose (these are in the mail). First study the xs of the spinal cord and dorsal root ganglion. Then grab a slide in the black slide box on the side table – there are only two so you’ll have to put them back in the black box. This slide has a section of the spinal cord dorsal root and dorsal root ganglion coming out of a least one side. Hints at orientation: the deep cleft (ventral median fissure) tells you that this portion is ventral (toward the floor, or anterior); the largest cells of the gray matter are the motor nuclei, which occur in the ventral horn. The outer portion (white matter) of the cord is filled with myelinated fibers (looking like small empty spaces). The inner gray matter has the cell bodies and is shaped like a butterfly. The ventral horn of the gray matter contains the large motor neuron cell bodies. These innervated the skeletal muscles. Also identify the dorsal median septum, central canal within the gray commissure, pia mater, arachnoid membrane, dorsal, lateral and ventral horns. Cell bodies of interneurons occur in the dorsal horn and cell bodies of sympathetic neurons are in the lateral horn of thoracic and some lumbar segments.
44 & 46. Medullated (myelinated) nerve and “peripheral nerve” ls and xs. In these slides you should be able to identify the nerve bundles, fascicles, epineurium, perineuium, endoneurium, myelin sheath, and axons. In long sections, you should be able to see the nodes of Ranvier: follow the neurons to see the breaks in them. These breaks are the nodes of Ranvier, which are regions where the myelin sheath is interrupted. The nerve action potential jumps from node to node. Also, you should see some blood vessels located between the axons. Can you see any preparatory artifacts that tell you how thick this slice is?
45. Nissl bodies. These are coarse, basophilic granules representing the endoplasmic reticulum and the free ribosomes of the neuron. These bodies should extend to the dendrites but will be seen only in limited supply in the axon hillock and the axon.
Nervous Continued, Digestion Start
- Long bone development – see the 2° centers of
ossification!
- Elastic cartilage – see the great stains of
elastin between the lacunae of elastic cartilage!
47. Protoplasmic
astrocytes. In this slide you’ll see a
lot of cell bodies and a tract of astrocytes (should be centrally located on
the slide). You’ll also see astrocytes
dispersed in the concentrations of cell bodies. Notice the shape of these
cells. What do these cells do?
48. Messner’s
corpuscles. These are kind of hard to
find in some of your slides. Don’t get these confused with the excretory duct
of a sweat gland. These occur at
extensions of the dermis (dermal
papillae) into the epidermis, and are receptors for fine touch. These appear like stacks of coins (membranous
appearance). The membranes are a sheath
that surrounds a sensory nerve ending.
49. Vater-Pacini (Pacinian) corpuscle. See also slide 60 and maybe slide 56. This is a large ovoid or round structure
found deep in the dermis or subcutaneous tissue of the skin or the
pancreas. Under low magnification, it
looks like a slice of onion because of its layers of lamellae. Identify the fibroblast cells (their nuclei
are dark staining in the lamellae), connective tissue sheath, inner bulb, and
lamellae.
50. Cerebellum. Hold this slide up and examine it. The cerebellum is the part that resembles the
branches of a tree. Examine this region
with low magnification and see the different layers. The outer layer is the molecular layer of the
cortex, and is separated from the next layer (granular layer of the cortex) by
large Purkinje cells. The granular layer
is so called because it is filled with nuclei.
Inside the granular layer is the white matter, seen as fibrous regions
made up of myelinated neurons. Note that
the relationships of white and gray regions are reversed in the brain from what
they were in the spinal cord.
51. Cerebral
cortex. Note that mostly nuclei are
seen. Blood vessels permeate through the
brain. Distinguish between the outer
gray (with large nerve cell bodies and nuclei) and inner white (with lots of
small dark nuclei) matter. Near the
junction of the white and gray (British say “grey”) matter, search for large
triangular pyramidal cells. The medulla
has predominantly small nuclei that belong to oligodendrocytes that myelinate
the neurons. The myelin is what makes
the white matter white looking.
10. Tongue. Find the surface epithelium (stratified
squamous), using low power. Two types of
glands occur among the skeletal muscle fibers in this region: mucous and serous
glands (both producing saliva). Mucous
glands have flattened basal heterochromatic nuclei and a “fluffy” white
cytoplasm. Serous glands have cells that
have a dark cytoplasm; with rounded euchromatic nuclei . Look for the ducts that extend toward the
surface. These ducts have a distinct
lumen and open into the epithelium at the bases of the invaginations. Small ducts have a simple cuboidal or
columnar epithelium, and larger ducts may have a columnar to stratified
cuboidal epithelium.
Papillae are large toad-stool-shaped structures covered with
the same stratified squamous epithelium typical of the rest of the tongue. Examine the papillae to find several circular
arrangements of cells (taste buds) at its lateral surfaces. Using the 40x objective, identify the
following components of the taste buds: taste pore, neuroepithelial (taste)
cell (with light, round nuclei), and sustentacular (supporting) cells (with
flattened dark nuclei).
52, and all the way back to 3. Esophagus. The lumenal lining consists of stratified
squamous epithelium. The mucosa consists
of the epithelium, lamina propria, and muscularis mucosae (which may be very
prominent to absent). It may contain
submucosal (mucous) glands and ducts (stratified cuboidal) leading to the
lumenal surface. The CT-filled submucosa
lies under the muscularis mucosae, and the muscularis externa, consisting of
inner circular and outer longitudinal layers of smooth (or skeletal) muscles,
lies outside of this. Depending upon
whether the section is taken from above or below the diaphragm, the outermost
layer will be adventitia (loose CT) or serosa (single layer of squamous
epithelium), respectively. The
muscularis externa will consist of skeletal muscle if taken from the upper
portion, or smooth muscle if taken from the lower part of the esophagus. The middle portion of the length of eh
esophagus consists of a mixed smooth muscle/skeletal muscle m. externa.
53. Left blank on
purpose. These slides are in the
mail. I will set up a demonstration
scope for the following: Gastro-esophageal
junction. Note the abrupt transition in
epithelial histology between the esophagus (stratified squamous epithelium) and
stomach (simple columnar epithelium, deeply invaginated to form mucus-secreting
cardiac glands). The surface epithelium
consists of mucus secreting cells, and these invaginate to form the gastric
pits. Cardiac lands empty into the
gastric pits. A bit further from the
esophagus, the glands change to become gastric (fundic) glands. They consist primarily of the parietal (dark
pink) and chief (light blue) cells.
External to the mucosa (consisting of epithelium, lamina propria, and
muscularis mucosae), lies the submucosa and the extensive muscularis externa of
smooth muscle.
54. Fundic
stomach. Ask to see a slide with rugae
if you want to see these. Note the major
layers from the lumen outward: mucosa containing gastric pits and gastric
glands, a thin lamina propria, and layers of m. mucosae arranged in different
directions; submucosa of loose CT; thick muscularis externa, and an outer
serosa. The mucosa has a surface
epithelium of mucus-secreting cells; it invaginates as gastric pits, which have
mucus-secreting cells. You can identify these because the cells have a light
pink apical surface, which is due to being filled with mucous granules. Several gastric (fundic) glands open into
each pit. The major cell types of the
gastric glands are the large parietal cells (fried egg appearance), and smaller
blue chief cells at the base of the glands.
55. Pyloric stomach.
The lumenal lining consists of simple columnar mucous-secreting
epithelium. Below this epithelium is a
huge collection of pyloric glands, which are of the branched or coiled tubular
mucous type, and lie in the lamina propria.
Below the glands are the muscularis mucosae, then the submucosa, and
muscularis externa layers. The
muscularis externa consist of inner circular and outer longitudinal
layers. The glands in the lamina propria
layer secrete mucus, which serves mainly for protection. In this pyloric region the inner circular
muscle is well developed to form the pyloric sphincter.
56. Duodenum. You will see finger-like projections, the
villi, which are lined by simple columnar epithelium. Look at the epithelial cells under higher
magnification. Note that the apex
(lumenal surface) has a thin pink outline, which you now know is the striated
(or brush) border and this appearance is due to a heavy layer of
microvilli. Note also the ovoid light
mucous (goblet) cells interspersed in this epithelium. The core of the villus contains the lamina
propria and some smooth muscle fibers. A
thick layer of intestinal glands (crypts of Lieberkühn) makes up much of the
mucosa. The cells making up these glands
have a less well-developed brush border than the surface epithelium. The muscularis mucosae are at the base of the
mucosa.
This lies adjacent to the submucosa which lies beside the muscularis
externa. The submucosa in the duodenum
is filled with mucus-secreting Brunner’s glands. The muscularis externa has a thick inner
circular layer and an outer longitudinal layer.
A serosa occurs around only a part of the cross section of the
duodenum. Most of the outer layer is
made up mostly of adipose (fat) tissue, and is the adventitia.
Note: these slides contain part of
the pancreas (dark glandular tissue) and the common bile duct is seen entering
the wall of the duodenum (obliquely, most likely in the preparation).
57 (Wards) & 58 (Carolina). Colon.
This looks like the rest of the intestine except for the following: no villi, lots of goblet cells; the
intestinal glands are mucous secreting, and often the outer longitudinal muscle
is thickened in some regions to produce the taenia coli in humans (haven’t seen
any yet in our slides). A serosa may or
may not be present depending upon the portion of the colon.
58. Liver. The unit of the liver is the lobule. To find the lobule, look for a hole that has
no distinct cellular lining, and into which many cells of channels seem to be
radiating. This is the center of the
lobule, the central vein, and sinusoids are the channels radiating into this
central vein. At the edge of the lobule
is a set of three vessels, the portal triad, consisting of branches of the
hepatic portal vein, the hepatic artery, and the bile duct. The bile duct has a simple cuboidal or short
columnar epithelial lining. The hepatic
portal vein is very thin walled, large and irregularly shaped, has a squamous
epithelial lining. The hepatic artery is
small, has the thickest wall of the three structures, and contains smooth
muscle, and again is lined by the squamous epithelium. This portal triad forms a corner between two
or three lobules. The lobule is made up
of cords or plates of hepatic cells (hepatocytes) separated from each other by
spaces or channels called sinusoids.
These all radiate into the central vein.
The sinusoids are lined by endothelial cells and contain blood and
phagocytic Kupffer cells. Note: while I refer to these as the central vein,
hepatic artery, hepatic portal vein, and bile duct, these are really small
branches of these vessels.
59. Pancreas. This gland has exocrine (with ducts) and
endocrine (w/o ducts) components. The
endocrine portion consists of pale pink aggregations of cells, each aggregate
being a pancreatic islet, or islet of Langerhans. This islet produces insulin, which is put
directly into the blood stream. The
remainder of the pancreas contains the exocrine portion, its ducts, and blood
vessels. The secretory product s make in
the acinus. The large ducts are lined
with either cuboidal or columnar epithelium.
The exocrine portion of the gland produces digestive enzymes.
3. Trachea. Also see the long section of trachea in the black slide box. The respiratory epithelium is pseudostratified ciliated columnar. The lamina propria consists of connective tissue with mucous glands. The hyaline cartilage is lined by perichondrium. The adventitia lies outside of the cartilage. A muscularis layer is present where cartilage is absent, and sometimes co-exists with it.
61. Human lung. Crappy slide – do your best. The lung consists mainly of spaces, called alveoli, where gaseous exchange occurs. Because of this, the alveolar walls are lined with capillaries. See if you can determine a pattern to the spaces in this slide. Bronchi have cartilage around within them. Bronchioles have no cartilage, and may retain the pseudostratified epithelium in the larger bronchioles. As they become smaller they become plain ciliated columnar or cuboidal epithelium. The respiratory bronchiole has alveoli (which exchange gases) coming off the wall. The respiratory bronchiole is cuboidal or squamous-lined, and opens into the alveolar duct and alveoli. They are lined mainly by squamous epithelium. Also, try to find pulmonary blood vessels. A pulmonary artery lies next to each part of the respiratory tube to the terminal bronchiole. Remember this carries deoxygenated blood to be oxygenated in the capillaries lining the alveoli. From here, the pulmonary vein leaves to go back to the heart. You may be able to find a pulmonary vein because it is a large blood vessel that is all by itself not associated with any specific part of the airway.
62, 63, 64. Kidney. Tough one. You may have to use all three slides to see the following features. Identify the cortex region versus the medulla. Medullary rays are extensions of the medulla that project into the cortex. They contain the collecting tubules and straight portions of the distal (called ascending thick limb) and proximal (descending thick limb) convoluted tubules. Identify the renal corpuscle and the convoluted tubules in the cortex. The renal corpuscle consists of coiled capillaries, the glomerulus, and a Bowman’s capsule, which is a squamous epithelium-lined sphere into which the glomerulus protrudes. The proximal convoluted tubules have cuboidal large, darkly-stained cells with a brush border, which projects into the lumen and therefore gives the lumenal border an indistinct appearance. The distal convoluted tubules have very few short microvilli on the lightly-stained low cuboidal epithelial cells, and therefore have a distinct straight lumen. As the DCT approaches the glomerulus from which it originated, it becomes modified into the macula densa, indicated by very closely packed cells and nuclei adjacent to the glomerulus. This region helps (I’ve learned just lately) regulate blood pressure and therefore urinary filtration rates. Also in the cortex are collecting tubules that have an arched cuboidal cell lining and the cells have distinct lateral borders. In the medulla, the collecting tubules are higher cuboidal or columnar, and still have distinct lateral borders. The medulla also contains the loops of Henle, which consists of a thick limb and a thin limb. The loop consists, in order, of a descending thick limb (similar in structure to the PCT), the thin limb of simple squamous epithelium, and an ascending thick limb with a structure like the DCT with which it is continuous. The simple squamous thin limb can be differentiated from capillaries by the rounded nuclei, distinct cytoplasm, and rounded profile of the tube in cross section.
65. Ureter. (Intentionally left blank - slides in the mail). There are two slides of ureter in the black box on the side table. Check them out and replace them when you are done. The innermost layer consists of transitional epithelium. Note the rounded surface of the lumenal epithelial cells and the apparent lining of the outermost layer of cells. Below the epithelium is the lamina propria of loose CT. The muscularis or muscular coat is made up of a thin inner longitudinal smooth muscle and a thicker outer circular layer. The outer adventitial consists mainly of adipose tissue and blood vessels.
8. Urinary Bladder. The bladder has a folded lumen (central space). This lumen is lined by transitional epithelium. Note the layers of epithelial cells. The outer layer of transitional epithelial cells (umbrella or dome cells) has an outer lining of dark material. This dark lining is formed by the invagination of the membranes to accommodate stretching of the cell when the lumen is expanded. In terms of layering, it is very similar to the ureter. Under the epithelium, there is a thick dense lamina propria, and a very thick muscular coat.
66 and 67. Testis. Look under low power. Some slides may have an entire cross section of a testis which might also include a ductus epididymis (see below). The testis is surrounded by a fibrous tunica albuginea, which encloses many profiles of seminiferous tubules in which sperm are made by mitosis and meiosis. Between seminiferous tubules are interstitial Leydig cells (which produce testosterone) and blood vessels. Use the next slide to examine the stages of sperm formation, but for now, look at a single tubule, and you do not have to identify the following stages. The basal region is lined with rounded spermatogonia which undergo mitosis to become primary spermatocytes (spotty nuclei), and then become the secondary spermatocytes by undergoing the first meiotic division. The secondary spermatocytes divide again (the second meiotic division) to become spermatids (with smaller, darker nuclei), which transform into mature spermatozoa. All these stages occur progressively toward the lumen. Mature spermatozoa have thin rod-like nuclei that are free in the lumen. Sertoli cells with large elongated nuclei lie 1/3 of the way up the tubule wall, and nourish the developing cells among many other things.
The next slide (67) will allow you to distinguish the different cell types. Note the thick tunica albuginea which invaginates as septa to form lobules. Between the many seminiferous tubules are blood vessels, fibroblasts, and Leydig cells, which have large round nuclei and may have light secretory granules (testosterone) in the cytoplasm. Since the tubules undergo waves of development of sperm, any profile may have different stages, so don’t expect to see all stages in each profile of the tubule. Identify the following: Spermatogonia: these occur along the outer edge. They have large round nuclei, with the nucleolus either central or along the nuclear membrane, and nucleoplasm either splotchy or dark.
Primary spermatocytes: These are large cells with thick chromosomes. The secondary spermatocytes occur in the short second meiotic division, so they are rarely seen.
Spermatids: have smaller nuclei which generally have two nucleoli. Nucleus gets smaller and denser until we have the mature spermatid, which has a very thin black nucleus and flagellum protruding into the lumen.
Sertoli cells: developing sperm cells attach to the cytoplasm of these cells for nourishment. The nuclei of Sertoli cells are large, ovoid or rectangular, along the middle of the tubule wall, and have a prominent large nucleolus
68. Epididymis. This consists of a single highly coiled tubule containing pseudostratified columnar epithelium and having sperm in the lumen. A basement membrane (may not be apparent) lines the outer surface of the epithelium, and a very thin layer of smoothe muscle cells lies outside the BM. This may not be present in the cranial end of the epididymis. The epithelial cells have long stereocilia (modified microvilli) projecting into the lumen.
69. Vas deferens (Ductus deferens). The lumen is line with pseudostratified columnar epithelium. Below the epithelium is a fibrous lamina propria enclosed by the very thin inner longitudinal, thick middle circular and thick outer longitudinal layers of smooth muscles.
70. Penis. Look under low magnification of this cross section to see the three bodies (corpora) making up most of the mass of the penis. These bodies are surrounded by a fibrous tunica albuginea. Two dorsal corpora cavernosa lie side by side, separated by a median septum. The ventral corpus spongiosum is easily recognizable because it contains the cavernous portion of the urethra, line by stratified columnar epithelium. The corpus spongiosum is filled with veins and little arteries. Locate the deep arteries in the medial portion of each corpus cavernosum, and the large superficial dorsal vein lying above the two corpora cavernosa. The epidermis lining the outside of the penis is stratified squamous epithelium, since it is skin, and the dermis of dense CT lies under it. The dorsal artery is seen in some preps.
71. Sperm smear. You have either bull, chicken or rat sperm. Identify the head and principal piece of the tail.
72. Ovary. Under low power, see different-sized spheres (ovarian follicle), each containing a large cell, the oocyte, and surrounded by one to several layers of follicle or granulose cells. The follicles lie in the stroma of the ovary. The largest follicle, the Graafian follicle, encloses a cavity (antrum) containing an albumen-like fluid. In this Graafian follicle, identify the cumulus oophorus, corona radiata, zona pellucida, and theca externa and interna. Id the small primordial follicle (single layer of squamous follicle cells around an oocyte); this is waiting to become activated to form a primary follicle. See also primary (one or more layers of granulosa [formerly follicle] cells) and secondary (with one to several cavities) follicles. Id a corpus luteum in your sections.
73. and 74. Uterus (Human early post-menstrual and resting stage). Compare the two stages. Note the innermost layer which is simple columnar epithelium. Just below is the lamina propria which contains profiles of uterine glands. The epithelium and lamina propria make up the endometrium. Below this is the myometrium, consisting of smooth muscle cells and blood vessels. The arteries are enlarged and tortuous, forming he coiled arteries.
2. Vagina. Find the mucosal folds and note the stratified squamous epithelium. Below the epithelium, you will find a thick lamina propria with blood vessels and possibly lymphoid tissue. Below the LP, you will find the interstitial, highly elastic CT imbedded with smooth longitudinal and then smooth circular (transverse) bundles of muscles. Adventitia is the outside layer.
75. Heart. When examining the heart, remember that the
plane of section will determine what you will see. Examine other slides to get an overview of
all the parts. Examine the slide under
low magnification or grossly and determine which is left vs. right ventricle
with the interventricular septum between.
Once you have determined this, follow the left ventricle up to it’s
opening. It will open into either the
atrium (directly above it) or the aorta (extending medially). Based on this, you may see either the
bicuspid (hanging down) or the semilunar valve (extending upward). If you have the right atrium, you may see the
vena cavae entering it. You may see
papillary muscles and chordae tendineae in the lumen of the ventricle. After identifying the parts of the left side,
examine the right side for the ventricle, atrium, tricuspid valves, pulmonary
trunk and its semilunar valves. The
layers of the heart are the epicardium, myocardium, and endocardium. The valves consist of endocardium only and
the thick myocardium is made up of cardiac muscle fibers.
76 & 77. Aorta (elastic and Mallory stains). The fat and loose CT that is in the
adventitia identifies the outer layer of the aorta. From the lumenal border
inward, there is a single layer of endothelial (squamous epithelial) cells and
fibrous CT. The elastic stain makes
elastic fibers black, but does not stain the nuclei so it is difficult to see
the endothelial cells. These two layers
make up the tunica intima. Outside of
this is the thicker tunica media, which is make up of smooth muscles in a
circular arrangement. The darker lines
and bundles are the elastic fibers, the innermost being an internal elastic
membrane that borders the tunica intima.
The tunica adventitia contains CT, nerves and blood vessels (vasa
vasorum, or, “vessels of the vessel”, and adipose cells.
78. Artery, Vein and Nerve.. Compare the relative thickness of the layers described
above between the artery and vein. Note
that the artery, but not the vein, has a thin internal elastic membrane located
within the tunica intima. The tunica
intima of the artery contains almost no CT.
The artery is usually small and round, with a thicker wall than the
vein. The vein is larger and irregular
in shape. The artery has a
well-developed layer of smooth muscle cells making up the tunica media. The vein may contain sporadic smooth muscle
within the media. Check other slides
in your box for arterioles, venules, and capillaries. Many times these can be found in
adventitia. Arterioles have a light pink
internal elastic lamina and 1-2 layers of smooth muscle cells around it. Capillaries have a lumen that is the size of
a nucleus, and only a ring of endothelial cells. The venules have smooth muscle cells that are
scattered in the wall. They do not form
a continuous layer. Capillaries consist
of only an endothelial cell, and the lumen is smaller than a red blood
cell. Larger arteries and veins may also
be seen. Notice the dark smooth muscle
cells. In veins, they are intermittent,
while arteries have a thick dark red layer of muslc fibers. Determine whether any valves occur in the
veins. In the submucosa of the gut, see
the thin walled lymphatic vessels with a lighter lumen that the artery or vein.
79 and slide 10. Rabbit and Monkey
tongue. Examine these slides for capillaries, arterioles and venules. Look for a longitudinal section of the
arteriole. What is the appearance of the
smooth muscle in this compared to the cross section?
80. Mammalian Blood Smear. Use the following to key out the cell types
in the blood:
1.
Pink, fairly small, round
à ERYTHROCYTE or RED BLOOD CELL.
2.
Tiny, dark, irregular in size and shape
à PLATELET or THROMBOCYTE
B.
Cell has a nucleus
à LEUKOCYTE or WHITE BLOOD CELL
1.
Nucleus makes up more than half of the cell volume
i.
Nucleus is not intensely dark; the cytoplasm is light blue with many fine
granules. The nucleus may be kidney
shaped or irregular; cells are very large
à MONOCYTE (3-8% of WBCs)
ii.
Nucleus is very dark, round or slightly indented; cell is slightly larger
than RBC
à LYMPHOCYTE
(30-35% of WBCs)
2.
Lots of cytoplasm, nucleus with lobes (GRANULOCYTES)
i.
Red granules in cytoplasm, nucleus with 2 lobes, pink cytoplasm
à EOSINOPHIL (2-5% of WBCs)
ii.
No granules of very pale granules; 2-7 lobes in nucleus; pink or pale
blue or gray cytoplasm
à NEUTROPHILS (60-70% of WBCs)
iii.
Large blue granules may hide nuclear shape
à BASOPHILS (0-1% of WBCs)
80 – 84. Survey of the blood of
vertebrates (fish blood is missing and will go into #84. Before you look at these slides think about
the RBC for a second. In mammals, the
nucleus is lost upon completion of development of the RBC. One hypothesis for
this is that because mammals are homeotherms, the energetic demands call for
higher carrying capacity of O2 in the blood.
Hence, mammals have lost their nucleus to take on more O2. Now, out of your other slides, which organism
would also be homeothermic (“warm blooded”) and which are heterotherms (“cool
blooded”)? What do you predict their
RBCs will look like? What do you
find? Can you explain this?
85. Bone marrow smear. Scan the slide under low magnification. Most of the cells are RBCs with no nucleus,
but a few are giant cells up to 20x larger than the RBCs – they also have a
multi-lobed nucleus. These usually occur
near the end of the smear and are the megakaryocytes (they get dragged along to
the last instant during preparation).
These cells release parts of their cytoplasm to provide the blood with
platelets.
Developmental stages. In development, the WBCs first are large with a
large ovoid nucleus, and this stage is called the myelocyte. It already has the adult type granules. The cells get smaller and the nuclei begin to
indent to form the metamyelocyte. In RBC
development, the cells get progressively smaller, and the nuclei get smaller
and more condense. A normoblast has a
pale bluish-pink cytoplasm and highly condensed nucleus. As hemoglobin develops in here, the
normoblast cytoplasm gets pinker and the nucleus smaller and darker. Finally, the nucleus gets extruded and the
pale blue-pink reticulocyte remains. It is slightly larger and slightly darker
than a normal RBC.
86. Coronary Artery. Observe this slide noting the above
information on arteries. This is the
artery that, interestingly, feeds oxygen to the heart.
Slide in black slide box. Observe the slide labeled “Arterial occlusion” in the black slide box. Compare this with the previous slide. The occlusion is a plaque build-up within the artery. If you want to view arteriosclerosis, let me know (I’ve got that slide too).
References:
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http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/histo_frames.htm
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