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The Cardiovascular System: Blood Vessels and Circulation © 2013 Pearson Education, Inc

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The Cardiovascular System: Blood Vessels and Circulation © 2013 Pearson Education, Inc PowerPoint® Lecture Slides prepared by Meg Flemming Austin Community College C H A P T E R 13 The Cardiovascular System: Blood Vessels and Circulation © 2013 Pearson Education, Inc. Chapter 13 Learning Outcomes • 13-1 • Distinguish among the types of blood vessels based on their structure and function. • 13-2 • Explain the mechanisms that regulate blood flow through blood vessels, and discuss the mechanisms that regulate movement of fluids between capillaries and interstitial spaces. • 13-3 • Describe the control mechanisms that interact to regulate blood flow and pressure in tissues, and explain how the activities of the cardiac, vasomotor, and respiratory centers are coordinated to control blood flow through tissues. © 2013 Pearson Education, Inc. Chapter 13 Learning Outcomes • 13-4 • Explain the cardiovascular system's homeostatic response to exercising and hemorrhaging. • 13-5 • Describe the three general functional patterns in the pulmonary and systemic circuits. • 13-6 • Identify the major arteries and veins of the pulmonary circuit. • 13-7 • Identify the major arteries and veins of the systemic circuit. © 2013 Pearson Education, Inc. Chapter 13 Learning Outcomes • 13-8 • Identify the differences between fetal and adult circulation patterns, and describe the changes in the patterns of blood flow that occur at birth. • 13-9 • Discuss the effects of aging on the cardiovascular system. • 13-10 • Give examples of interactions between the cardiovascular system and the other organ systems. © 2013 Pearson Education, Inc. Vascular Pathway of Blood Flow (13-1) • Arteries leave the heart and branch into: • Arterioles feed parts of organs and branch into: • Capillaries, where chemical and gaseous exchange occurs, and which drain into: • Venules, the smallest vessels of the venous system, which drain into: • Veins, which return blood to the atria of the heart © 2013 Pearson Education, Inc. Three Layers of Vessel Walls (13-1) 1. Tunica intima (or tunica interna) • Has endothelial lining and elastic connective tissue 2. Tunica media • Has smooth muscle with collagen and elastic fibers • Controls diameter of vessel 3. Tunica externa (or tunica adventitia) • Sheath of connective tissue may anchor to other tissues © 2013 Pearson Education, Inc. Figure 13-1 A Comparison of a Typical Artery and a Typical Vein. Tunica externa Tunica externa Tunica media Tunica media Tunica intima Tunica intima Smooth muscle Lumen of vein Smooth Muscle Lumen of artery Endothelium Endothelium Elastic fiber ARTERY Artery and vein LM x 60 VEIN © 2013 Pearson Education, Inc. Elastic Arteries (13-1) • First type of arteries leaving the heart • Examples are pulmonary trunk, aorta, and major branches • Have more elastic fibers than smooth muscle • Absorb pressure changes readily • Stretched during systole, relaxed during diastole • Prevent very high pressure during systole • Prevent very low pressure during diastole © 2013 Pearson Education, Inc. Muscular Arteries and Arterioles (13-1) • Muscular arteries • Examples are external carotid arteries • Tunica media contains high proportion of smooth muscle, little elastic fiber • Arterioles • Tunica media has only 1–2 layers of smooth muscle • Ability to change diameter controls BP and flow © 2013 Pearson Education, Inc. Capillaries (13-1) • Tunica interna only • Endothelial cells with basement membrane • Ideal for diffusion between plasma and IF • Thin walls provide short diffusion distance • Small diameter slows flow to increase diffusion rate • Enormous number of capillaries provide huge surface area for increased diffusion © 2013 Pearson Education, Inc. Figure 13-2 The Structure of the Various Types of Blood Vessels. Large Vein Elastic Artery Internal elastic layer Tunica Tunica externa Endothelium intima Tunica media Tunica media Endothelium Tunica intima Tunica externa Medium-Sized Vein Muscular Artery Tunica externa Tunica externa Tunica media Tunica media Endothelium Endothelium Tunica intima Tunica intima Venule Arteriole Smooth muscle cells (Tunica media) Tunica externa Endothelium Endothelium Basement membrane Capillary Endothelial cells Basement membrane © 2013 Pearson Education, Inc. Capillary Beds (13-1) • An interconnected network of capillaries • Entrance to bed is regulated by precapillary sphincter, a band of smooth muscle • Relaxation of sphincter allows for increased flow • Constriction of sphincter decreases flow • This occurs cyclically, referred to as vasomotion • Control is local through autoregulation © 2013 Pearson Education, Inc. Figure 13-4 The Organization of a Capillary Bed. Vein Collateral Smooth arteries muscle cells Venule Small artery Arteriole Capillaries Arteriole Section of a precapillary sphincter Small venule Capillary Capillary bed LM x 125 beds This micrograph shows a number of capillary beds. Precapillary sphincters KEY Consistent blood flow Arteriovenous anastomosis Variable blood flow Features of a typical capillary bed. Solid arrows indicate consistent blood flow; dashed arrows indicate variable or pulsating blood flow. © 2013 Pearson Education, Inc. Alternate Routes for Blood Flow (13-1) • Formed by anastomosis, a joining of blood vessels • Arteriovenous anastomosis bypasses capillary bed, connecting arteriole to venule • Arterial anastomosis occurs where arteries fuse before branching into arterioles • Ensures delivery of blood to key areas, brain, and heart © 2013 Pearson Education, Inc. Veins (13-1) • Collect blood from tissues and organs and return it to the heart • Venules are the smallest and some lack tunica media • Medium-sized veins • Tunica media has several smooth muscle layers • In limbs, contain valves • Prevent backflow of blood toward the distal ends • Increase venous return © 2013 Pearson Education, Inc. Veins (13-1) • Large veins • Thin tunica media and thick collagenous tunica externa • Thinner walls than arteries because of low pressure © 2013 Pearson Education, Inc. Figure 13-5 The Function of Valves in the Venous System. Valve closed Valve opens above contracting muscle Valve closed Valve closes below contracting muscle © 2013 Pearson Education, Inc. Checkpoint (13-1) 1. List the five general classes of blood vessels. 2. A cross section of tissue shows several small, thin-walled vessels with very little smooth muscle tissue in the tunica media. Which type of vessels are these? 3. What effect would relaxation of precapillary sphincters have on blood flow through a tissue? 4. Why are valves found in veins, but not in arteries? © 2013 Pearson Education, Inc. Maintaining Adequate Blood Flow (13-2) • Flow maintains adequate perfusion of tissues • Normally, blood flow equals cardiac output (CO) • Increased CO leads to increased flow through capillaries • Decreased CO leads to reduced flow • Capillary flow influenced by pressure and resistance • Increased pressure increases flow • Increased resistance decreases flow © 2013 Pearson Education, Inc. Pressure (13-2) • Liquids exert hydrostatic pressure in all directions • A pressure gradient exists between high and low pressures at different points • Circulatory pressure, high in aorta vs. low in venae cavae • Arterial pressure is blood pressure • Capillary pressure • Venous pressure • Flow is proportional to pressure gradients © 2013 Pearson Education, Inc. Resistance (13-2) • Any force that opposes movement • Circulatory pressure must be high enough to overcome total peripheral resistance • Highest pressure gradient exists in arterioles due to high peripheral resistance • Vascular resistance • Viscosity • Turbulence © 2013 Pearson Education, Inc. Vascular Resistance (13-2) • Largest component of peripheral resistance • Caused mostly by friction between blood and vessel walls • Amount of friction due to length and diameter of vessel • Length doesn't normally change • The longer the vessel, the higher the resistance • Arteriolar diameter is primary source of vascular resistance • The smaller the diameter, the greater the resistance © 2013 Pearson Education, Inc. Viscosity (13-2) • Due to interactions between molecules and suspended materials in a liquid • Low-viscosity fluids flow at low pressures • High-viscosity fluids flow only under high pressures • Blood viscosity is normally stable • Changes in plasma proteins or hematocrit can alter viscosity and, therefore, flow © 2013 Pearson Education, Inc. Turbulence (13-2) • Eddies and swirls in fluid flow • In smooth-walled vessels turbulence is low • Slow flow near the walls, faster flow in center • Injured or diseased vessels or heart valves show increase in turbulence and decrease in flow • Turbulent blood flow across valves produces the sound of heart murmurs © 2013 Pearson Education, Inc. Interplay of Pressure and Resistance (13-2) • Blood pressure is maintained by hormonal and neural mechanisms • Adjusting diameter of arterioles to specific organs: • Regulates peripheral resistance • Regulates flow • Allows for matching flow and perfusion to tissue needs © 2013 Pearson Education, Inc. Blood Pressure (13-2) • Arterial pressures fluctuate • Systolic pressure (SP) is peak and occurs during ventricular contraction • Diastolic pressure (DP) is the minimum and occurs at the end of ventricular relaxation • Recorded as systolic over diastolic (e.g., 120/80 mm Hg) • Pulse is alternating changes in pressures © 2013 Pearson Education, Inc. Pulse Pressure (13-2) • The difference between systolic and diastolic pressures • Pulse pressure = SP – DP • Diminishes over distance, eliminated at the capillary level • Arterial recoil or elastic rebound occurs during diastole
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