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Chapter 13 Blood Vessels & Circulation

Chapter 13 Blood Vessels & Circulation. Blood vessel anatomy. Three layers Tunica Interna : innermost layer Tunica Media : smooth muscle Tunica Externa : connective tissue; stabilization within tissues Vasoconstriction : arterial contraction; diameter decreases

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Chapter 13 Blood Vessels & Circulation

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  1. Chapter 13 Blood Vessels & Circulation

  2. Blood vessel anatomy • Three layers • Tunica Interna: innermost layer • Tunica Media: smooth muscle • Tunica Externa: connective tissue; stabilization within tissues • Vasoconstriction: arterial contraction; diameter decreases • Vasodilation: arterial relaxation; diameter increases

  3. arteries • Elastic arteries: elastic fibers for stretching (high systolic pressures, i.e. aorta, pulmonary trunk) • Muscular arteries: supply blood to muscles and organs (i.e. carotid) • Arterioles: have thin tunica media

  4. capillaries • Vital functions at the capillary level: chemical and gaseous exchange between the blood and interstitial fluid takes place across capillary walls • Diameter: 8 µm (~1 RBC) • Thin walls: slows blood flow for exchange; one layer of cells (no media/externa) • Capillary beds: network of capillaries; autoregulated by precapillary sphincters

  5. veins • Return blood to the heart • Venules: smallest veins; <50µm lack tunica media • Medium-sized veins: 2-9mm; has tunica media and thick tunica externa • Large veins: 2 venae cavae& 3 tributaries; thin media, thick externa • Low pressure; valves in medium veins prevent back flow and increase venous return • Damaged valves: varicose veins & hemorrhoids

  6. Clinical note: arteriosclerosis • Focal Calcification: aging causes calcification of tunica media • Atherosclerosis: increased level of lipids in blood circulation can lead to formation of plaques • Treatment options: medication, surgery (angioplasty, stent, bypass), LIFESTYLE CHANGE http://www.youtube.com/watch?v=S9AqBd4RExk http://www.youtube.com/watch?NR=1&v=MGzyhuCs43o&feature=fvwp

  7. Factors affecting blood flow • Resistance: oppositional force; inverse correlation; inc. resistance  dec. blood flow • Vascular: friction of walls • Viscosity: fluidity of blood • Turbulence: disruption in smooth blood flow • Pressure: force against vessel walls; direct correlation; inc.pressure  inc. blood flow • Arterial (blood pressure) • Capillary • Venous

  8. Cardiovascular pressures • Capillary: (Fig. 13-7) • Arterial end (high P) • Venous end (low P) • Diffusion, filtration, and osmosis drive exchange • Venous: • Low pressure compared to arterial flow • Must overcome gravity • Muscle compressions and respiratory increase venous return • Arterial: • Normal BP: 120/80 • Systolic: ventricular systole (120 mmHg) • Diastolic: end of ventricular diastole (80 mmHg) • Pressure decrease from aorta to arterioles (120  30)

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