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Lecture 7-9 Blood Vessels.docx - Blood Vessels Lecture 7...

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Blood VesselsLecture 7Types of blood vessels (3 main types of blood vessels)Arteries: 3 main types.Following types of arteries go from biggest to smallest-Elastic: largest of arteries. They leave the heart (aorta, pulmonary trunk, and slightlyoff the branches of those)oMore stretching ability than other arteries-Muscular: majority of our arteries. Contain thick smooth muscle walls which are ableto vasodilate or vasoconstrict to change the direction the blood flows in body-Arterioles: these are the arteries before they reach capillaries. Smallest arteriesCapillaries: form network/beds where gas, nutrient, & waste exchange occurs. Onlypoint in system where things leave/enter the blood.Veins:these go from smallest to largest-Venules: smallest of veins. On other side of capillaries-Small veins:-Medium or large veinsNOTE: Great vein entering the heart is known as thesuperior vena cavaBlood vessel structureHas 3 layers:1.Tunica interna (or tunica intima)-Innermost layer. Closest to the blood (or luma/tube of the blood vessel)-Largest feature is a layer of simple squamous epithelial cells which line thelumen (or inside of our blood vessels) calledendothelial cells2.Tunica media-Surrounds the tunica interna. This is the middle layer-We have smooth muscle and elastic fibers-This layer changes dramatically when we go from arteries to veins (thethickness and # of elastic fibers change)this layer disappears in capillaries3.Tunica externa-Outermost layer. It contains CT which attaches blood vessels onto otherstructures-CT varies as we go through the 3 different types of vessels-Nerve supply to our vessels are here-Comparing blood vessel structureTunica interna:Endothelial cells line everything! (artery, veins and capillaries)-The layer is similar in all vessels exceptveins
-In veins we have extensions of the endothelial layer which moves into lumenoThe extensions make flaps which create a valve system, why? in veins wehave low pressure, so it stops blood going in wrong directionBasement membrane: attaches all the epithelial cells together. It’s a network of collagenfibers-If we have damaged endothelial cells, the basement membrane of collagen fibers getexposed causing platelets to stick on to it to start forming a clot-This causes plaque to build up inside the blood vesselsleading to heart strokeIn arteries only, the next layer is theinternal elastic lamina: elastic fibers which surroundthe tunica interna-it contains holes to allow NT to reach the smooth muscle in tunica media to activateitNOTE:capillaries are only made of endothelial cells and basement membrane, why? it’s keptthin to allow efficient gas exchangeTunica media:Smooth muscle: runs in a circle around the lumen so when they contract they make thediameter of the blood vessel smaller-In arteries: smooth muscle can be very thick (40 layers of cells thick)-In veins: smooth muscle is only 1-2 layers thick, why? they don’t vasodilate orvasocontrictExternal elastic lamina:only present in arteries.

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Term
Winter
Professor
Dr. Howard
Tags
Common carotid artery, Blood vessel

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