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Lecture 23


Blood Vessels 3 layers-endothelium, vascular smooth muscles,connective tissue. Capillaries only have endothelium.
Types of Blood Vessels Arteries,arterioles, capillaries,veins.Each has a diff func. Lymph vessels carry excess filtered fluid.
Physical Factors Some factors constant, such as vessel length. Some factors variable. flow=pressure/resistance
Vessel Radius Most important variable factor. Resistance ~ 1/radius. Small constriction causes large inc. in resistance raises flow. Short blockages can compensate w/ inc velocity until ~ 80% closed.
Viscosity Thickness of blood. Controlled by hemotocrit. (% RBC's in blood, 45 males, 42 females)-need large change to influence blood flow. Above 48% RBC interaction w/ arteriole walls greatly inc. resistance.
Arterial Conductance High pressure blood enters aorta at ~ 93 mmHg. Large arteries expand to hold blood, little change in BP, 2-4 mm wide. Momentum of moving blood carries blood forward to tissues.
Arterial Pressure Systolic P is 120 mmHg, diastolic P is 80 mmHg. Pulse pressure is sys-dias: 120-80=40 mmHg. Mean arterial pressure = dia + 1/3 pp=80+13=93mmHg
Coronary Circulation Heart rate dependent lowers diastole at high HR. lowers filling time and lowers coronary flow. Coronary flow only occurs during diastole HR>180. dec. cardiac output, potential heart failure.
Atherosclerosis Multiple stages: 1:LDL, low density lipoprotein, lays down fatty streak. 2:WBC's and fibroblasts overgrow fatty streaks. 3:calcium infiltration hardens overgrowth hardening of the arteries.
Alcohol Effect Modest alcohol intake can solubilize fatty streak, can reverse atherosclerosis. Stage 1: Biophysical effect, not receptor effect. No alcohol effect on other stages.
Arteriolar Flow Arterioles branch off arteries-30 microns wide, 93 mmHg at artery end. Carries blood to capillaries:37 mmHg at capillary end. Arteriole radius can go in either direction
Tone Partial activation w/ no stimulus. Can relax (vasodilate) or contract (vasoconstrict)
Perfusion Control Symp neurons, metabolites. Paracrines control arteriole smooth muscle. NE, adenosine, NO
Created by: danamarie9323