BISC306 Lecture Notes - Lecture 4: Perfusion, Pulse Pressure, Tunica Externa
25 Oct 2017
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Document Summary
Poiseuille"s law describes flow rate alone a length of tube. P=pressure n= viscosity: however, blood vessels are not simple tube. In smaller vessels like capillaries the relationship breaks down and the relative viscosity is less for a given hematocrit. Structure of blood vessels: epithelium that lines the vessels s called the endothelium. Arteries- pressure reservoirs: the arteries more elastic than other vessel types. This helps to maintain pressure and therefore blood flow during diastole. Arterioles- resistance vessels: arterioles are relatively muscular, local regulation of arteriolar smooth muscle tone determines perfusion rate to downstream capillaries, animals regulate the tone of arteriolar smooth to control blood pressure by adjusting peripheral resistance. Capillaries- exchange vessels: the diffusion distance between the capillary lumen and the interstitium is very short. Vein: veins are very compliant at physiological pressures, veins are far more compliant than arteries at low pressure.
