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Define the term artery and vein. Be able to compare and contrast these vessels
- Artery any blood vessel that conduct blood away from the heart.
- Vein Any blood vessel that carries blood toward either atrium fo the heart.
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Distinguish between: A portal system and an arteriorvenous anastomosis?
Portal system blood flows through two consecutive capillary networks before returning to the heart. Portal systems occur in the kidneys. 2 capillary beds
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Ateriorvenous anastomosis (shunt), blood flows from an artery directly into a vein and bypasses the capillaries. Shunts found in fingers palms toes and ears where they reduce heat loss in cold weather by allowing warm blood to bypass these exposed surfaces No capillary beds
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Distinguish between the characteristics of the tunics in arteries and veins:
- Artery: Tunica intima (interna) scalloped, simple squamous endothelium.Conducting arteries are the biggest.examples are aorta, common carotid and subclavian, pulmonary trunk, common iliac.
- Thin layer elastic fibers called internal elastic lamina found between intima /media but sparse.
- Tunica Media: middle layer usually the thickest. consists of smooth muscle, collagen and some elastic tissue.Basic function are to strenghen the vessels and prevent the blood pressure from rupturing them and provide vasomotion (changes in diameter of blood vessels. Consists of 40 to 70 layers of elastic sheets.
- Tunica externa (tunica adventitia) outermost layer. Loose muscle CT that merges with blood vessels nerves and other organs. Anchors vessels and provides passage for small nerves, lymphatic vessels, and smaller blood vessels called vasa vasorum -supply blood to at least the outer half of the wall of the larger vessel. Tunica externa is relatively thick and well supplied with vasa vasorum.
- Veins: Tunica interna simple squamous White blood cells leave to transit out. Not very scalloped.medium veins exhibit infoldings forming venous valves directed towards heart.
- Tunica media smooth muscle no elastic. Thin 2/3 layers of muscle not under alot of pressure.
- Tunica externa (adventitia) relatively thick, fat too. veins collapse when empty and are flattened because walls are thin not under lot of pressure.
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