Vessels and Pressure

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Vessels and Pressure

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 27 Current Lecture  Blood Vessels o o Tension in wall of vessels proportional to radius and pressure insideconclusion: aorta gives a lot of wall tension where as a capillary is not very much tension in the walls. Aneurisms only occur in arteries o 3 have smooth muscle: arteries and arterioles and veins  vascular smooth muscle is capable of contracting and not contracting (vaso constriction and dilation)  vasoconstriction of arteries and arterioles increases resistance to blood flow make it possible to redirect blood flow in systemic system. Regional vasoconstriction will redirect blood flow one way or the other (after a meal vasodilation in intestine is coming from other areas that are inducing vasoconstriction o 2 do not: capillaries and venules  Microcirculation o o Dow from the top and across from the right and up is the flow o The artery is heavily reinforced by strong fibrous connective tissue o Arterioles don’t have this protective sheath o Smooth muscle cells can generate force for long periods of time can maintain contraction all night and day long o Always contracted to some extent 24 hours a day o The amount of contraction is called MUSCLE TONE o Capillaries have no smooth muscle besides the pre-capillary sphincters that regulate the amount of blood flowing through the capillaries o In most tissues, most cells are no further than a couple cells away from a capillary o In order to get from the arteries to the veins it gets though either arteriovenous bypasses or thoroughfare channels o Inner diameter of the capillaries is about the size of a red blood cell o Some white blood cells are actually bigger so they must go through these other channels instead of capillary beds

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