VascularPhysiology

VascularPhysiology - Vascular Physiology Overview Humans...

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Vascular Physiology
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Overview Humans have a closed circulatory system. Vessels form a continuous space bounded  by plasma membranes and basement  membranes. Arteries carry blood away from the heart. Veins carry blood to the heart. Capillaries lie between the arteries and  veins and are the site of material  exchange.
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Structure The structures of the walls of arteries and  veins are similar to each other. The walls have three layers, or tunics,  from the lumen out: Tunica intima Tunica media Tunica externa The composition of these three tunics  differs between arteries and veins.
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Structure The tunica intima is composed of: Endothelium – simple squamous epithelium Subendothelial layer – basement membrane and  loose connective tissue The tunica media is composed of circularly  arranged smooth muscle cells. The tunica externa is composed of loose  connective tissue infiltrated with nerves,  blood vessels (vasa vasorum), and lymphatic  vessels.
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Structure
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Differences The walls of arteries and veins differ in  that: Arteries have in internal and external elastic  lamina on either face of the tunica media. The tunica media of arteries is much thicker  than that of veins. The tunica intima of veins has folds that  extend into the lumen and form valves. The walls of arteries tend to hold their shape,  while the valls of veins tend to collapse.
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Arteries There are several types of arteries: Elastic (conducting) arteries are thick walled  arteries nearest the heart.  They have thick  elastic lamina, and are low resistance.  They  tend not to vasoconstrict. Muscular (distributing) arteries have thinner  elastic lamina and make up the bulk of the  larger arteries of the body Arterioles are the smallest arteries that feed  directly into capillaries.
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Veins There are several types of veins: Venules are the veins just beyond the  capillaries.  They have thin walls and allow  the passage of leukocytes into the  surrounding tissue. Veins have thicker walls and conduct blood  back to the heart.  Veins have valves to  prevent the backflow of blood.
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Capillaries Capillaries are the smallest vessels and  consist of only the tunica intima. The outer wall of a capillary is stabilized by  smooth muscle-like cells called pericytes. There are three types of capillaries: Continuous capillaries Fenestrated capillaries Sinusoidal capillaries
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Continuous Capillaries Continuous capillaries are the most common  in the body.  They have: Tight junctions between the endothelial cells that  prevent the movement of cell sized bodies out of 
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This note was uploaded on 04/15/2011 for the course BIOL 2301 taught by Professor Kasparian during the Spring '10 term at North Texas.

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VascularPhysiology - Vascular Physiology Overview Humans...

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