test_3_updated notes - VESSELS CHAP 21 Blood vessels form a...

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VESSELS CHAP 21 Blood vessels form a network of tubes that carry blood away from the heart, delivering O2 to the tissues through the capillaries and then returning it , deoxygenated , to the heart. OVERVIEW: Heart arteries arterioles metarteriole capillaries venules veins heart ARTERIES: a. vessels carrying blood away from the heart b. usually, this blood is oxygenated c. large diameter d. 3 layers ( tunicas ) of tissue make up the artery wall. 1. TUNICA INTIMA (INTERNA): deepest tunica consisting of ENDOTHELIUM = single layer of epithelial cells lining the heart and vessels, and an INTERNAL ELASTIC MEMBRANE 2. TUNICA MEDIA: usually thickest layer consisting of SMOOTH MUSCLE and in some vessels, an EXTERNAL ELASTIC MEMBRANE 3. TUNICA EXTERNA (ADVENTICIA): elastic and collagen fibers Due to this anatomy and the presence of elastic fibers, arteries will expand during ventricular systole and recoil during ventricular diastole and a PULSE can be detected (The alternate expansion and recoiling of elastic arteries after each ventricular systole of the left ventricle creating a pressure wave that travels through the arteries). A pulse can be detected in a superficial artery that lies over a bone or other firm tissue. Common pulse locations= ARTERIOLES and METARTERIOLES a. small arteries b. connect arteries with capillaries c. Important in the regulation of flow of blood through the capillaries CAPILLARIES: (exist thoughout the body EXCEPT lens, cornea, epithelium, cartilage) a. Composed of single layer of endothelium b. Lumen size large enough to allow one RBC to flow per unit time - allows for diffusion of gases in and out of RBC (decreased velocity) c. exist in capillary beds ( capillary networks) - when tissue needs are low, blood will flow only through a small portion of the network. When needs increase, the entire capillary bed is full of blood. Regulated by _________________________________.
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There is gas exchange occurring at the tissue level and there is BULK FLOW of large amounts of ions, proteins, other nutrients and water. The bulk flow OUT of the capillary occurs at the arteriole end. At the venule end, the fluid moves INTO the capillary from the tissue spaces. In health, approximately 85% of the fluid at the arteriole ends of the capillaries is reabsorbed at the venule end. Some of the escaped fluid and proteins will be returned to the blood via the lymphatic system Approximately 20 liters of fluid filters out of the capillaries each day, 17 liters will be reabsorbed by the capillary and 3 liters enter the lymphatics. Occasionally, the balance between this filtration and reabsorption of the interstitial fluid is interrupted, and less than normal fluid is reabsorbed. This abnormal increase in interstitial fluid is termed EDEMA. POSSIBLE CAUSES OF EDEMA
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This note was uploaded on 03/18/2012 for the course PHYSICS 222654 taught by Professor Virginiahall during the Fall '10 term at University of Texas at Austin.

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test_3_updated notes - VESSELS CHAP 21 Blood vessels form a...

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