Term
Blood Vessels 3 layers:
and the exception |
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Definition
- Tunica intima
- Tunica media
- Tunica adeventitia
***capillaries are exception- only have tunica intima resting on basal lamina |
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Term
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Definition
Single layer of endothelial cells
Underlying subendothelial loose CT |
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Term
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Definition
Mostly smooth muscle cells- can regulate BP
-Elastic fibers, type III collagen, and proteoglycans |
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Term
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Definition
- Becomes continuous with CT surrounding vessels
- Fibroblasts
- Coll. type I fibers
- Longitudinally oriented elastic fibers
- Vasa vasorum
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Term
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Definition
-In tunica adventitia
-Supplies adventitia and media
-Necessary b/c larger vessel layers too thick to occur solely by diffusion
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Term
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Definition
1. Elastic (conducting)- aorta and branches
2. Muscular (distributing)- named arteires
3. Arterioles (and meta-arterioles)- regulatory into capillaries |
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Term
| Why elastic arteries need to be elastic |
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Definition
Systole- contraction, high pressure
Dystole- relaxation, low pressure
*Recoil- Windkessel effect- serves to maintain arterial pressure and flow of blood through tissues |
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Term
| What makes elastic arteries elastic? |
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Definition
Tunica media- layers of smooth muscle intercalated by elastic laminas
-Appears wrinkly- streaightens when strecthed |
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Term
| In tunica media of elastic and muscular BVs, the smooth muscle cells are connected via: |
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Definition
| Gap junctions- allows coordinated contraction (like heart) |
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Term
| What are absent in tunica media and intima of blood vessels? |
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Definition
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Term
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Definition
Weak spot in aortic wall causes false lumen
*Marfan syndrome- mutation in fibrillin gene--> bad elastic fibers |
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Term
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Definition
- Separates tunica intima from media
- Only found in arteries, not veins
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Term
| Muscular Arteries include: |
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Definition
| Major arteries, except those coming off aortic trunk and terminal bification of abdominal aorta |
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Term
| Identifying characteristic of muscular arteries |
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Definition
| Relatively thick tunica media composed of mostly smooth muscle cells |
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Term
| Arterioles- elastic lamina and smooth muscle description |
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Definition
- No external elastic lamina
- Eventually lose internal elastic lamina
- Branch into metarterioles- discontinuous layer of smooth muscle
- *If any muscle cells around vessel- it is metarteriole and NOT capillary
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Term
| Differences b/t vein and artery vessel walls and histologically |
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Definition
Veins have smaller tunica intima
***Veins have much smaller tunica media
*Veins have lots of smooth muscle in adventitia
Histologically, veins have:
Thinner walls
Larger lumen
Veins may have blood cells in cross section |
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Term
| Vein valves purpose and structure |
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Definition
Prevent backflow due to lower pressure
Valves- portion of intima jutting into lumen
-Reinforced with collagen and elastic fibers
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Term
| Why do you walk around during a long flight to prevent blood clots? |
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Definition
More valves in veins- fight gravity
-Contraction of skeletal muscle squeezes vein, increasing blood pressure in that section-->upstream (source) valve closes, downstream valve opens -->blood flow
Walking helps pump blood back to heart |
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Term
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Definition
Valves fail to close properly, blood pools in vein
Over time, pooling forces vein walls outward-->enlargement, bulging, rope like appeareance of veins
Factors:
Women>men due to skeletal muscle differences
Overweight- more pressure on SVC
Pregnant women should sleep on their side |
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Term
| Capillaries main function: |
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Definition
***Enable gas, water, nutrient, waste exchange b/t blood and surrounding tisse
Due to small size |
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Term
| Virtually all cells of the body are within 0.01mm of a capillary except |
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Definition
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Term
| 5 micron diameter of capillaries means RBCs |
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Definition
RBCs are 8 microns
Must fold to enter capillary- spectrin and ankrin |
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Term
| 2 examples of non-nutritional function of capillaries |
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Definition
1. Glomeruli of kidney- capillary flow forms glomerular filtrate
2. Skin- local body temperature- hand in hot water |
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Term
| Shunt to bypass true capillaries |
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Definition
Metarteriole-thoroughfare channel
Closed- wound
Open- heat |
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Term
| Regulation of blood flow into capillaries by: |
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Definition
Local and systemic signals:
Vasodilation- NO
Vasoconstriction- NE via ANS |
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Term
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Definition
-NOT muscle, just contractile unit
-Contain actin, myosin, tropomyosin
-Capillaries lack tunica media- pericytes instead
-Surrounded by basal lamina continous with basal lamina of endothelial cells |
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Term
| 3 types of capillaries (least to most leaky) |
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Definition
1. Continuous (least leaky)
2. Fenestrated
3. Sinusoidal (most leaky)-->bone marrow |
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Term
| Continuous (somatic) capillaries |
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Definition
-Least leaky, most common
-Location: muscle, brain, thymus, bone, lung
-Caveolae
-Transcytosis
-Continuous basal lamina |
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Term
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Definition
More permeable to water and small solutes than non-fenestrated capillaries
-Location: where rapid exchange occurs- kidney, endocrine gland, intestine
-*Always continuous basal lamina- faces BV lumen and basal lamina
-->Sleeving effect |
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Term
| Discontinuous (Sinusoidal) Capillary |
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Definition
a. No diaphragms
b. No pinocytotic vesicles- not necessary
c. Endothelial cells form discontinuous layer separated by wide spaces
d. ***Interchange b/t blood and tissues greatly facilllitated by structure of capillary wall
e. *Irregular blood pools or channels that conform to shape of structure in which they are located
f. ****Found mainly in liver, hematopoietic organs like BM and spleen
i. Megakaryocytes, new blood cells pass through holes
g. *Discontinuous basal lamina |
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Term
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Definition
anything larger than 500 daltons can’t go through
• Very extensive tight junctions
• ***Tight junctions resemble tight junctions of epithelial cells
• No diffusion through cleft or via vesicles
• Few pinocytotic vesicles
• *Astrocytes secrete factors that induce capillary endothelial cells to produce extensive tight junctions
o Several areas of brain not “behind” BBB- pineal gland→secretes melatonin into systemic circulation |
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