Chapter 52

Summary		Questions		Media Resources
52.1 The circulatory systems of animals may be open or closed.
• Vertebrates have a closed circulation, where the blood stays within vessels as it travels away from and back to the heart. • The circulatory system serves a variety of functions, including transport, regulation, and protection.		1.  What is the difference between a closed circulatory system and an open circulatory system? In what types of animals would you find each?		• Heart Transplant
52.2 A network of vessels transports blood through the body.
• Plasma is the liquid portion of the blood. A variety of plasma proteins, ions, metabolites, wastes, and hormones are dissolved in the plasma. • Erythrocytes, or red blood cells, contain hemoglobin and function to transport oxygen; the leukocytes, or white blood cells, function in immunological defenses. • The heart pumps blood into arteries, which branch into smaller arterioles. • Blood from the arterial system empties into capillaries with thin walls; all exchanges between the blood and tissues pass across the walls of capillaries. • Blood returns to the heart in veins, which have one-way valves to ensure that blood travels toward the heart only. • Lymphatic vessels return interstitial fluid to the venous system.		2.  What are the major components of blood plasma? 3.  Describe the structure of arteries and veins, explaining their similarities and differences. Why do arteries differ in structure from veins? 4.  What is the relationship between vessel diameter and the resistance to blood flow? How do the arterial trees adjust their resistance to flow? 5.  What drives the flow of fluid within the lymphatic system, and in what direction does the fluid flow?		•Blood Vessels A •Blood Vessels B •Capillary Bed Anatomy A •Capillary Bed Anatomy B •Lymphatic System •Lymphoid Organs •Lymphatic System •Erythrocytes •Leukocytes •Arteries and Arterioles •Capillaries •Blood •Lymph System • Artificial Blood
52.3 The vertebrate heart has undergone progressive evolutionary change.
• The fish heart consists of four chambers in a row; the beat originates in the sinus venosus and spreads through the atrium, ventricle, and conus arteriosus. • In the circulation of fishes, blood from the heart goes to the gills and then to the rest of the body before returning to the heart; in terrestrial vertebrates, blood returns from the lungs to the heart before it is pumped to the body.		6.  Describe the pattern of circulation through a fish and an amphibian, and compare the structure of their hearts. What new circulatory pattern accompanies the evolution of lungs?		•Exploration: Evolution of the Heart •External Heart Anatomy A •External Heart Anatomy B •External Heart Anatomy C •Internal View of Heart A •Internal View of Heart B •Internal View of Heart C •Internal View of Heart D •Types of Systems •Human Heart •Heart •Mammal and Bird Circulation
52.4 The cardiac cycle drives the cardiovascular system.
• Electrical excitation of the heart is initiated by the SA (sinoatrial) node, spreads through gap junctions between myocardial cells in the atria, and then is conducted into the ventricles by specialized conducting tissue. • The cardiac output is regulated by nerves that influence the cardiac rate and by factors that influence the stroke volume.		7.  How does the baroreceptor reflex help to maintain blood pressure? How do ADH and aldosterone maintain blood volume and pressure? What causes their secretion?		•Human Circulatory System •Plaque •Cardiac Cycle Blood Flow (normal speed) •Cardiac Cycle Blood Flow (slow motion) •Blood Flow •Cardiac Cycle •Heart-Electrical Pathway

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