Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 19 The Cardiovascular System: Blood Vessels P A R T A

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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  Arteries and veins are composed of three tunics 1. tunica intima – internal most layer 2. 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 Figure 19.1b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vascular Components Figure 19.2a, b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 Figure 19.3b

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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  If  P increases, blood flow speeds up; if  P decreases, blood flow declines  Blood flow is inversely proportional to resistance (R)  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. Blood flow – the volume of blood flowing through a vessel 2. Pressure – force per unit area exerted against a vessel containing blood (mm Hg.) 3. 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 Figure 19.5

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 Figure 19.6

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 Figure 19.11

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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