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class notes 4.12 - Biology 1006 Blood passes through the...

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Biology 1006: 4/12/2010 Blood passes through the heart twice: o First pass is to the lungs to be oxygenated o Second time pumped much more forcefully to be called to all parts of the body Layer of fat on the outside of the heart is normal Vessels: o Connective tissue- elastic and made up of collagen fibers o Smooth muscle- can change the diameter of the blood vessel, for expansion (dialation) and contraction o Edothelium- single layer of cells, a lining of cells Arteries: o Have much more elastic tissue and thicker smooth muscle, carries blood under pressure Veins: o Under low pressure o deoxygenated blood o larger blood vessels than arteries o less connective tissue because don’t need to be as elastic o thinner smooth muscle layer Capillaries: where blood is exchanged o Composed only of endothelium o Allows for the exchange of gases o Passage of small muscles
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Veins have such a thin layer of connective tissue and smooth muscle layers that you can sometimes see through them As you move, it keeps pumping blood back into the heart, muscle contraction causes blood to move When you don’t move, blood pools and can cause people to pass out Varicose vein: A lot of pressure because of standing still for long periods of time or for
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