CRR Histology Lab 3
I. Connective Tissue (and blood vessels)
CRR Week 3
Today we look at ordinary connective tissue (this page) and also blood vessels (on reverse side of this page).
You are encouraged to use a reference (i.e., histology atlas) for basic orientation to conspicuous features of each slide.
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Slide 2, scalp
Slide 3, skin
(EASY) Find adipocytes. Question--Where should you
look? (Fat cells are not typically found in dermis.)
(REVIEW) In dermis, distinguish cells from extracellular
material. Question--How much of the dermis consists of
extracellular material (connective tissue matrix)?
(REVIEW) Distinguish epidermal derivatives (hair
follicles, sebaceous glands, sweat glands) from dermal
connective tissue. Question--What kind of tissue are
these epidermal derivatives?
(HARD, maybe impossible) Identify a particular
connective tissue cell. Question--What types of
connective tissue cells may occur in skin, or in connective
tissue generally? Which ones are typically more
common? Question--Can you identify any of these cell
types? (Small, dark nuclei among collagen fibers may be
fibroblasts; cells bigger than a typical fibroblast, with
noticable cytoplasm, may be macrophages; round nuclei
without evident cytoplasm, especially if there are several
such nuclei close together, are probably lymphocytes.)
(REVIEW) Find collagen. Question--How does collagen
stain on H&E histological specimens? Question--Where
is ground substance?
(EASY) Note how the texture of collagen changes across
the thickness of the dermis. Distinguish between
papillary and reticular layers of the dermis. Note
connective tissue "papillae" which project upward into
corresponding hollows in the base of the epidermis
(HARDER) Find an arrector pili. (This inconspicuous bit
of smooth muscle is eosinophilic but should look
distinctly different from collagen.)
(EASY) Find an artery and a vein. Hint: Look deep.
Look for "tubes" with blood cells inside. (But note that
vessels are often empty, with blood washed away during
sample preparation. Also, blood may sometimes appear
outside vessels, due to tissue damage during sample
preparation.)
(HARDER) Find some capillaries. Hint: There should
be lots, especially in the papillary layer of the dermis, but
they may be extremely inconspicuous. Often a single
RBC is the best clue to the presence of a capillary.
(HARD) Find a nerve. Hint: Look deep. Individual
nerve fibers innervating the epidermis are typically too
thin to notice. Nerves are larger bundles of many fibers
(axons), all surrounded by a fibrous connective tissue
sheath. Question--Do the axons in this nerve belong to
sensory or motor nerve cells? Explain why.
At your discretion, you may notify an instructor
for a brief oral evaluation on this material.
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Slide 25, cornea (front surface of eyeball)
Slide 29, tongue
Slide 61, trachea (also slide 62)
Slide 43, colon
Slide 63, pelvis of kidney
If smooth or skeletal muscle occurs on the slide, can you
distinguish the muscle from collagen? (Use your text or
atlas to learn where to look.)
On each of these speciments, find connective tissue
immediately beneath the epithelium. Also find connective
tissue elsewhere on the slide. Question -- How do these
connective tissues differ from one another? (Note the
varying proportions of cells, collagen, and ground
substance.)
Look for white and brown fat in the renal pelvis.
Can you find / recognize cartilage in the wall of the
trachea? (Use your text or atlas to learn where to look.)
At your discretion, you may notify an instructor
for a brief oral evaluation on this material.
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ELECTRON MICROGRAPHS
Use Rhodin's Atlas of Histology (from the Learning Resources Center) or other any other collection of electron micrographs.
Rhodin's Atlas is also available online, at < http://projects.galter.northwestern.edu/rhodin/ >
Find several examples of connective tissue. In each
example, identify cells and matrix. Within the matrix,
distinguish collagen and ground substance.
At your discretion, you may notify an instructor
for a brief oral evaluation on this material.
Find examples of connective tissue in which you can locate
one or more of the following: fibroblast, adipocyte, mast
cell, macrophage, and lymphocyte.
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For blood vessel exercises, see part II. on reverse side of this page.
CRR Histology Lab 3
II. Blood vessels (and connective tissue)
CRR Week 3
Today we look at blood vessels (this page) and also ordinary connective tissue (on reverse side of this page).
You are encouraged to use a reference (i.e., histology atlas) for basic orientation to conspicuous features of each slide.
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Many capillaries should be present in most connective tissues (the cornea is an exception). Unfortunately, capillaries are
commonly inconspicuous in most histological specimens. Question--Why are capillaries inconspicuous? (What structures
would you need to see to recognize a capillary?)
Look for larger blood vessels, both arteries and veins, deeper in the body, more than a millimeter from surface epithelium.
For each vessel you find, try to see the three layers -- intima, media, and adventitia. In any artery/vein pair, the vessel
with the thicker media, containing more smooth muscle, should be the artery. Arteries should also have an internal elastic
lamina, which may (or may not) be clearly visible. Blood cells may or may not be present within vessels. Also note the
differing appearances of endothelium, visible as cell nuclei lying at the margin between intima and lumen.
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Especially large and easily identified vessels should be
present in most of the specimens listed below.
Because arteries and veins tend to travel in parallel, look
for paired vessels of similar size and orientation.
Slide 20, Cerebral cortex. Look in the sulcus, in the
connective tissue between the two "lobes" (gyri) of the
specimen. Blood cells may appear black on this slide.
Slide 29, Tongue. Search for larger vessels deep within the
skeletal muscle that comprises the body of the tongue.
Slide 34, Esophagus. Look in the submucosa, the loose
connective tissue between the mucosa (the layer which
includes the epithelial surface) and the muscularis externa
(the thick smooth muscle layer).
Slide 39, Jejunum. Look in the submucosa, the loose
connective tissue between the mucosa (the layer which
includes the epithelial surface) and the muscularis externa
(the thick smooth muscle layer).
Slide 42, Pancreas. Look in the bands of connective tissue
which separate lobes of glandular epithelium. Here ducts
should be distinguished from blood vessels. Ducts are lined
by cuboidal or columnar epithelium, in contrast to the
simple squamous endothelium that lines blood vessels.
Slide 43, Large intestine. Look in the submucosa, the
loose connective tissue between the mucosa (the layer
which includes the epithelial surface) and the muscularis
externa (the thick smooth muscle layer).
Slide 54, Aorta. This specimen is a piece of the wall of the
aorta, stained to reveal elastic tissue. Contraction of elastin
often bends sections so the intima is on the convex surface.
Slide 55, Artery, vein, nerve. This specimen is our "ideal"
example for examining blood vessel structure. The tissue
has been stained to show elastin (so vessels on this slide
appear different from those on standard H&E slides.)
Slide 56, Atherosclerosis. This is a pathological specimen,
an artery in which the intima is abnormally thickened (and
the lumen correspondingly narrowed). To appreciate
intimal thickening, identify smooth muscle of the
muscularis. Everything between the muscularis and the
lumen is intima.
Slide 60, Lung. Recall that pulmonary circulation is
distinct from systemic circulation. Because blood pressure
is lower in pulmonary than in systemic vessels, the walls of
pulmonary vessels are correspondingly thinner. Pulmonary
arteries look like systemic veins, and pulmonary veins are
more delicate still.
Slide 62, Trachea. In the loose connective tissue beneath
the tracheal epithelium there may be a venous plexus,
several relatively large venous vessels not paired with
arteries.
Slide 63, Kidney pelvis. For this lab, ignore the kidney
proper and look for blood vessels in the adipose connective
tissue that fills the hilus.
Slide 91, Adrenal gland. In this specimen, look for
arteries in the connective tissue outside of the gland and
veins in the central medulla. (These arteries and veins are
connected by narrow sinusoids between cords of adrenal
epithelial cells.) Curiously, the veins in the adrenal medulla
have a unique structure, with smooth muscle forming
several distinct longitudinal bands.
The circulatory system serves the entire body, so blood
vessels may also be found on nearly any other slide.
At your discretion, you may notify an instructor
for a brief oral evaluation on this material.
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ELECTRON MICROGRAPHS
Find examples of capillaries or other small vessels. Note appearance of endothelium and red blood cells.
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For connective tissue exercises, see part I. on reverse side of this page.