Lab 7 Cardiovascular System: 1) Index 2) Introduction 3) Things to identify 4) Muscular Arteries ... 5) Arterioles 6) Elastic Arteries 7) Capillaries 8) Medium Sized Veins 9) Large Veins 10)Venules .. 11) Lymphatic Vessel 12) Heart 13) Practical

 

Capillaries

 

a. continuous capillaries in skeletal muscle or mesentery

# 95 - Tongue, human, fungiform papillae, 1.5um, h-e

# 41 - Skeletal muscle, human, c.s. and l.s., h-e

# 75 - Capillaries, omentum, mammal, c.s.. h-e

 

On slide 95 and 41, find an area in which the skeletal muscle fibers are cut in cross section. Examine the loose connective tissue between the muscle fibers, the endomysium, for the presence of capillaries. In muscle, these are continuous capillaries with no fenestrations. Note that the lumen of a capillary usually is only wide enough to admit one or at most two erythrocytes. The nuclei of the endothelial cells often bulge into the lumen. Vessels of larger diameter with no smooth muscle layers are likely to be venules.

Examine Slide 41 and note the capillaries and arterioles running between the skeletal muscle fibers. What are the differences among endothelial cells, pericytes, and smooth muscle cells? Can you distinguish among these cell types on your slides.

References: Gartner, p. 161, Fig. 3; p. 146 - 147; p. 146 - 147 Wheater, p. 145, Fig. 8.11 (mesenteric) p. 146, Fig, 8-12

 

b. fenestrated capillaries in the adrenal gland

# 146 - Adrenal, rabbit, 1.5um, h-e

If needed, # 221 - Adrenal gland, rabbit, 1.5um, h-e

 

With the aid of your atlas locate the connective tissue capsule and the cluster of cells just under the capsule in the region called the zona glomerulosa. This would be best done at low magnification. Just under the zona glomerulosa, the cells are arranged in columns as the zona fasciculata. In betweeen the cells in the zona fasciculata are long, fenestrated capillaries. Locate these structures. They can be identified by the presence of erythrocytes.

Reference: Gartner, p. 198, Fig. 1

 

This is a slide of the Adrenal Gland. The blue arrow is showing another example of a capillary. Notice the Red Blood Cells lining up .

Blue arrow - Capillary

Adrenal Gland (capillary)

 

. fenestrated capillaries in the thyroid gland

# 158 - Thyroid gland, human, 1.5um, h-e

If needed # 160 - Thyroid and parathyroid, cat, h-e

 

Use your atlas to identify follicles. They are enclosed by simple cuboidal epithelium. Find capillaries cut in longitudinal and cross section in the connective tissue between follicles. Find capillaries in the connective tissue which surrounds the organ. In endocrine glands capillaries are fenestrated to allow rapid interchange of substances.

Reference: Gartner, p. 211, Fig. 2

 

Here is a slide of a tissue catching a cross section of a capillary. The blue arrows are pointing to the endothelial cell nuclei, that are lining the small vessel. What is the logic behind classifying this as a capillary? We can call it a capillary by using our "Red Blood Cell Ruler". There is only one RBC in the lumen of the vessel and it pretty much spans the whole width of the vessel. Therefore, this has to be a capillary because RBC pass through capillaries in single file to allow maximal exchange.

HINT: When ever you see just one RBC fitting across the width of the vessel, it is a capillary.

Blue arrows - endothelial cells lining capillary

 

 

Here is a slide from Cardiac muscle, used in a precious lab. In the image we can see a longitudinal section of a capillary, white arrows. Can you see the RBC lining up in single file? One RBC spans the entire width of the the vessel, so even at this low mag we can conclude that it is a capillary.

White arrows - Longitudinal Sect. Capillary

 

Capillary (single Red Blood Cell)

Cardiac Muscle (logitudinal sect. Capillary)