16 Cv Peripheral circulation

16 Cv Peripheral circulation - PERIPHERAL CIRCULATION page...

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PERIPHERAL CIRCULATION AC Brown page 1 A7b INTRODUCTION A. Cardiovascular System Functions 1. Transport metabolic substrates from their source (e.g. alimentary tract, lungs, liver) to the tissues that utilize them (e.g. muscles, brain) 2. Transport metabolic end products (e.g. carbon dioxide, urea, heat) to the organs that dispose of them (e.g. lungs, kidneys, liver, skin) 3. Transport endocrines from the organs that secret them to their target tissues 4. Provide a short diffusion distance between the vascular system and the cells 5. Contribute to maintaining the consistency of the cells' internal environment (e.g. interstitial fluid) – Homeostasis B. General Schematic (note pressure drop from arteries to veins) C. Components 1. Heart : develop the pressure needed to move blood around the cardiovascular system (overcome blood viscosity); continuously refresh capillary blood 2. Arteries : distribute blood pumped by the heart to the microvascular bed 3. Arterioles and associated structures: sites of controlled resistance; control the flow to individual vascular beds 4. Capillaries : exchange material between blood and interstitial fluid 5. Venules and Veins : collect blood from vascular beds and return it to the heart 6. Lymphatics : collect fluid and other substances from tissue and return it to the circulation
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PERIPHERAL CIRCULATION AC Brown page 2 A7b INTRODUCTION (continued) D. Pressure, Flow, and Resistance 1. Pressure: Force/Area; measured in mmHg (= torr), cmH 2 O, kPa (kilopascals); represents potential energy which can be converted to kinetic energy (movement of blood) Systolic pressure: highest pressure in a cardiac chamber or blood vessel during a cardiac cycle Diastolic pressure: lowest pressure in a cardiac chamber or blood vessel during a cardiac cycle 2. Flow a. volume flow (Q): volume of blood passing a given location in the circulation per unit time b. Cardiac Output: Q of either ventricle (not both); same as Q at any level of the circulation (typically 5 liters/min for a young adult of average size at rest) c. velocity of individual cells in the circulation (v): depends cross sectional area (A); decreases as A increases
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PERIPHERAL CIRCULATION AC Brown page 3 A7b D. Pressure, Flow, and Resistance (continued) 3. Resistance (R): frictional resistance to blood flow; due to blood viscosity Pressure Î Flow Î Heat difference Δ P Q potential kinetic dissipation of energy energy energy (friction, viscosity) a. define: R = Δ P / Q, where Δ P = pressure difference
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16 Cv Peripheral circulation - PERIPHERAL CIRCULATION page...

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