Answers to Review Questions - Chapter 42 1. What are the functions of red blood cells (erythrocytes)? Of white blood cells (leukocytes)? Of platelets (thrombocytes)? Red blood cells are involved in gas transport (oxygen, carbon dioxide). White blood cells play a role in the body's immune defenses. Platelets are involved in blood clotting. 2. What are the three types of granular leukocytes? Describe the characteristics and one significant function of each. Neutrophils have granules that appear neutral when stained. They are the principal phagocytic cells in the blood. Eosinophils have granules that stain bright red. They function in detoxifying foreign proteins and other substances - involved in allergic reactions and parasitic infections. (any one of those functions…) Basophils have deep blue granules when stained. They play a role in allergic reactions - release histamine in injured tissues and in allergic responses. Also can produce heparin to prevent blood from clotting. (any one of those functions…) 3. What are the two types of agranular leukocytes? Describe the characteristics and one significant function of each. Lymphocytes do not have granules - have round nuclei. Produce antibodies, destroy foreign cells. (any one of those functions…) Monocytes are the largest WBC - leaves the circulation to become a macrophage. Major function is phagocytosis of foreign cells/materials. 4. Describe the flow of blood through the heart, beginning with where the deoxygenated blood enters the heart and ending with where the newly oxygenated blood leaves the heart to be delivered to the body tissues. Right atrium → right ventricle → pulmonary trunk → lungs → pulmonary veins → left atrium → left ventricle → aorta 5. Describe the pathway of electrical activity through the conducting system of the heart. The sinoatrial node initiates the heartbeat, causing an action potential to spread through the atria to the atrioventricular node; this action potential causes the atria to contract. The action potential then spreads from the atrioventricular node through specialized muscle fibers (bundle branches, purkinje fibers) into the ventricles, and the ventricles contract. 6. What are the names of the four valves within the heart? Where is each located? Be specific for each of the four valves. Right atrioventricular valve (tricuspid) - located between the right atrium and right ventricle. Left atrioventricular valve (bicuspid or mitral) - located between the left atrium and left ventricle. Pulmonary semilunar valve - located between the right ventricle and the pulmonary trunk. Aortic semilunar valve - located between the left ventricle and the aorta. 7. What prevents backflow of blood through the atrioventricular valves? The leaflets of the valves are anchored to the floor of the ventricles via string-like structures called chordae tendineae. 8. What prevents backflow of blood through the semilunar valves? The cup-shaped cusps of the semilunar valves collect with blood as it begins to be pulled back toward the ventricle - this causes the cusps to snap tightly together.