Term
| What are the 3 layers that compose blood vessels? |
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Definition
1) Tunica intima- innermost containing endothelium and underlying connective tissue called "subendothelium," oriented longitudinally
2) Tunica media- smooth muscle cells that secrete collagen and elastin, oriented circumferentially around lumen
3) Tunica adventitia- longitudinal, loosely organized lay er consisting of smooth muscle, fibroblasts and connective tissue (vasculature and innervation penetrates this layer). |
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Term
What are the major differences b/w
1) Elastic Arteries
2) Muscular Arteries
3) Arterioles |
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Definition
1) Conducting Vessels (Aorta and Major branches)
-Receive blood from heart under high pressure (thick media)
-Relaxation/contraction spreads out force of beat and permits steady flow
-Aortic Aneurism results from abnormal stretching
2) Distributing Vessels
- Shifts blood among organs with little elastin in the thick tunica media.
- Can be identified by internal elastic lamina and a minimum of 4 smooth muscle layers
- Arteriosclerosis occurs when intima thickens and elastin, collagen and smooth muscle components are lost- can be predicted by hypercholesteremia
3) Resistance Vessels
- Major determinents of systemic blood pressure
- Regulate blood access to capillary beds
- Thinner tunica media (1-4 layers) with no subendothelial tissue and only whips of adventia.
- Stimulated by NE via alpha-1 adrenergic receptors
- Local regulation of blood flow to capillary beds by myogenic response (increased wall pressure leads to contraction and vice versa). |
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Term
| What factors determine arteriole contraction/dilation? |
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Definition
This is the "intrinsic myogenic response"
-Increased wall pressure causes endothelial cells to release endothelin for vasoconstrction.
- Decreased wall pressures causes endothelial cells to release NO and prostacyclin for valodilation. |
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Term
| Which type of artery is most critical for determining systemic blood pressure? |
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Definition
Arterioles!
-Brain perfusion maintained by NE signaling through a1-adrenergic receptors.
- contraction/relaxation regulated by intrinsic myogenic response |
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Term
| What physiological changes occur when blood leaves arterioles and enters capillary beds? |
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Definition
1) Total volume is greater
2) BP drops to 20 mm Hg
3) Gas/Nutrient exchange
** A notable amount of blood bypasses capillary beds via "metarteriole thoroughfare channels." Sometimes, anastamosis have the same effect, like in the case of the skin and thermoregulation. ** |
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Term
| How might you distinguish Continuous Capillaries from other capillary cells? |
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Definition
1) No breaks in walls with continuous basal lamina
2) Numerous caveolin-coated vesicles (caveolae)
3) Found in brain, muscles, bones, lung, testes and thymus. |
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Term
| How might you distinguish Fenestrated Capillaries from other capillary cells? |
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Definition
1) 10-100nm diameter fenestrae with protein diaphragms that span them.
2) Continuous basal lamina
3) Found in organs with high fluid and macromolecule flow across endothelium such as intestinal villi, chorid process and synovial membrane. Also characteristic of endocrine glands that secrete hormones.
*Glomeruli of kidney is special case!* |
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Term
| How might you distinguish Discontinuous Capillaries from other capillary cells? |
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Definition
1) Holes through both endothelial cell and basal lamina
2) Found in LIVER for traffic of lipoprotein particles b/w hepatocytes and blood and
in SPLEEN for movement of RBCs out of splenic pulp back to sinusoids. |
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Term
| WHy are valves and endothelial folds critical in venous circulation but not in arterial circulation? |
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Definition
| - Veins are very distensible and therefore have lower pressure circulation. These features prevent backflow! |
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Term
| What occurs to post-capillary blood as it enters Venules? |
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Definition
| - Post-capillary blood is taken up by these cells, where it slows, allowing for the extravasation of white blood cells out of the blood stream, b/w lateral border of endothelial cells and into connective tissues. |
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Term
| How might you distinguish Muscular, Capacitance Veins from Large, Elastic Veins? How can you distinguish both from arteries? |
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Definition
- Muscular veins have very thick adventia, while the elastic veins contain elastic tissue in the media and adventitia (all 3 layers thinner than arterial counterparts, however).
- Remember, 2 layers of smooth muscle in the media make it a vein and not an artery
- Frequently collapsed in tissues |
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Term
| What is Edema and how does it arise? |
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Definition
Drainage issue! Excess fluid accumulation in interstitial spaces between cells.
- High BP can force more fluid into capillary wall
- Starvation (protein especially) can result in Kwashiorker, where edema is due to decreased plasma proteins.Without adequate osmotic forces from these proteins, water leaks out of capillaries.
- In Burn victims, extensive capillary damage permits fluid and protein to leak out. The proteins generate an osmotic force which draws more fluid in |
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Term
How do you identify Lymphatic vessels?
How does the Lymph system work (generally)? |
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Definition
1)
- Only tunica intima with wisp of adventitia
- Lumens filed with pale, homogenous, eosinophillic material
- Never see RBCs
- Rely on valves (like veins)
2)
- 1-way system designed to collect excess interstitial fluid.
- Lymph vessels converge at thoracic duct, which empties into the right atria. |
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