Cardiovascular System: Blood Vessels PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Cardiovascular System: Blood Vessels Part A...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Cardiovascular System: Blood Vessels Part A 19 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Blood Vessels ▪ Blood is carried in a closed system of vessels that begins and ends at the heart ▪ The three major types of vessels are arteries, capillaries, and veins ▪ Arteries carry blood away from the heart, veins carry blood toward the heart ▪ Capillaries contact tissue cells and directly serve cellular needs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Generalized Structure of Blood Vessels ▪ Arteries and veins are composed of three tunics – tunica interna, tunica media, and tunica externa ▪ Lumen – central blood-containing space surrounded by tunics ▪ Capillaries are composed of endothelium with sparse basal lamina Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Generalized Structure of Blood Vessels Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.1b  Tunics ▪ Tunica interna (tunica intima) ▪ Endothelial layer that lines the lumen of all vessels ▪ In vessels larger than 1 mm, a subendothelial connective tissue basement membrane is present ▪ Tunica media ▪ Smooth muscle and elastic fiber layer, regulated by sympathetic nervous system ▪ Controls vasoconstriction/vasodilation of vessels Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Tunics ▪ Tunica externa (tunica adventitia) ▪ Collagen fibers that protect and reinforce vessels Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Elastic (Conducting) Arteries ▪ Thick-walled arteries near the heart; the aorta and its major branches ▪ Large lumen allow low-resistance conduction of blood ▪ Contain elastin in all three tunics ▪ Withstand and smooth out large blood pressure fluctuations ▪ Allow blood to flow fairly continuously through the body Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Muscular (Distributing) Arteries and Arterioles ▪ Muscular arteries – distal to elastic arteries; deliver blood to body organs ▪ Have thick tunica media with more smooth muscle and less elastic tissue ▪ Active in vasoconstriction ▪ Arterioles – smallest arteries; lead to capillary beds ▪ Control flow into capillary beds via vasodilation and constriction Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillaries ▪ Capillaries are the smallest blood vessels ▪ Walls consisting of a thin tunica interna, one cell thick ▪ Allow only a single RBC to pass at a time There are three structural types of capillaries: continuous, fenestrated, and sinusoids Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Continuous Capillaries Figure 19.3a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Fenestrated Capillaries Figure 19.3b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Sinusoids Figure 19.3c Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillary Beds Figure 19.4a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Capillary Beds Figure 19.4b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Blood Flow Through Capillary Beds ▪ Precapillary sphincter ▪ Cuff of smooth muscle that surrounds each true capillary ▪ Regulates blood flow into the capillary Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Venous System: Venules ▪ Are formed when capillary beds unite ▪ Allow fluids and WBCs to pass from the bloodstream to tissues ▪ Venules have one or two layers of smooth muscle (tunica media) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Venous System: Veins ▪ Veins are: ▪ Formed when venules converge ▪ Composed of three tunics, with a thin tunica media and a thick tunica externa consisting of collagen fibers and elastic networks Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Venous System: Veins ▪ Veins have much lower blood pressure and thinner walls than arteries ▪ To return blood to the heart, veins have special adaptations ▪ Large-diameter lumens, which offer little resistance to flow ▪ Valves (resembling semilunar heart valves), which prevent backflow of blood ▪ Venous sinuses – specialized, flattened veins with extremely thin walls (e.g., coronary sinus of the heart and dural sinuses of the brain) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Systemic Blood Pressure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.5  Factors Aiding Venous Return Figure 19.6 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings