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PowerPoint® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College CHAPTER Elaine N. Marieb Katja Hoehn 19 PART A Human Anatomy & Physiology SEVENTH EDITION Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Cardiovascular System: Blood Vessels Blood Vessels Circulatory System is considered a closed system Major vessels are arteries, capillaries, and veins Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Generalized Structure of Blood Vessels 1. 2. Arteries and veins are composed of three tunics tunica intima – internal most layer tunica media – middle layer Vasoconstriction – reduce lumen size Vasodilation – increase lumen size 3. tunica externa Lumen – central blood-containing space surrounded by tunics Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Generalized Structure of Blood Vessels Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.1b Vascular Components Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.2a, b Continuous Capillaries Continuous capillaries are abundant in the skin and muscles Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Continuous Capillaries Continuous capillaries of the brain: Constitute the blood-brain barrier Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fenestrated Capillaries Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.3b Venous System: Venules Venules are formed when capillary beds unite Allow fluids and WBCs to pass from the bloodstream to tissues Postcapillary venules – smallest venules, composed of endothelium and a few pericytes Large venules have one or two layers of smooth muscle (tunica media) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Venous System: Veins Lower blood pressure Large-diameter lumen Valves Venous sinuses – specialized, flattened veins with extremely thin walls (e.g., coronary sinus of the heart and dural sinuses of the brain) 65% of body blood supply is found in the veins – capacitance vessels Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Anastomoses Alternate pathways to body area if a branch is blocked Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Blood Flow, Blood Pressure, and Resistance Blood flow (F) is directly proportional to the difference in blood pressure (P) between two points in the circulation Blood flow is inversely proportional to resistance (R) If P increases, blood flow speeds up; if P decreases, blood flow declines If R increases, blood flow decreases R is more important than P in influencing local blood pressure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Flow, Pressure and Resistance 1. 2. 3. Blood flow – the volume of blood flowing through a vessel Pressure – force per unit area exerted against a vessel containing blood (mm Hg.) Resistance – opposition to flow as the blood passes through the vessels (viscosity, length and diameter) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Systemic Blood Pressure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.5 Arterial Blood Pressure Systolic pressure – pressure exerted on arterial walls during ventricular contraction Diastolic pressure – lowest level of arterial pressure during a ventricular cycle Pulse pressure – the difference between systolic and diastolic pressure Mean arterial pressure (MAP) – pressure that propels the blood to the tissues MAP = diastolic pressure + 1/3 pulse pressure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Factors Aiding Venous Return Venous BP alone is too low to promote adequate blood return and is aided by the: Respiratory “pump” Muscular “pump” Valves prevent backflow during venous return PLAY InterActive Physiology ®: Anatomy Review: Blood Vessel Structure and Function, pages 3–27 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Factors Aiding Venous Return Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.6 Short-Term Mechanisms Vasomotor center – medulla detects changes in the size of lumen Cardiovascular - alters cardiac output and blood vessel diameter Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Short-Term Mechanisms: Chemical Controls Oxygen and carbon dioxide Aortic and carotid areas Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Kidney Action and Blood Pressure Kidneys act directly and indirectly to maintain long-term blood pressure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Palpated Pulse Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.11 Measuring Blood Pressure Systemic arterial BP is measured indirectly with the auscultatory method A sphygmomanometer is placed on the arm superior to the elbow Pressure is increased in the cuff until it is greater than systolic pressure in the brachial artery Pressure is released slowly and the examiner listens with a stethoscope Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Measuring Blood Pressure The first sound heard is recorded as the systolic pressure The pressure when sound disappears is recorded as the diastolic pressure PLAY InterActive Physiology ®: Measuring Blood Pressure, pages 3–12 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Alterations in Blood Pressure Hypotension – low BP in which systolic pressure is below 100 mm Hg Hypertension – condition of sustained elevated arterial pressure of 140/90 or higher Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings