Chapter 42 Circulation and Gas Exchange Concept 42 1 Circulatory systems link exchange surfaces with cells throughout the body Transport systems functionally connect the organs of exchange with the body cells Gastrovascular Cavities Simple animals like cnidarians have a body wall only 2 cell layers thick between external environment and gastrovascular cavity Gastrovascular cavity functions both in digestion and circulation Figure 42 2 More complex animals have two types of circulatory systems Open circulatory system blood bathes the organs directly o Example arthropods and most molluscs Closed circulatory system blood is confined to vessels and is distinct from the interstitial fluid Figure 42 3 o Example some invertebrates and all vertebrate Both of these types of systems open and closed have three basic Vertebrate Circulatory Systems Figure 42 4 and 42 5 Circulatory System Parts components o A circulatory fluid blood o A set of tubes blood vessels o A muscular pump a heart mix with each other Clicker Q An open circulatory system allows blood to and interstitial fluid to Concept 42 2 Coordinated cycles of heart contraction drive double circulation in mammals Figure 42 6 Figure 42 7 The Cardiac Cycle o The mammalian cardiovascular system o The mammalian heart Cardiac cycle rhythmic contraction and relaxation of the heart Systole contraction or pumping phase Diastole relaxation or filling phase Figure 42 8 Cardiac Cycle Controls Electrical impulses coordinate the cardiac cycle Pacemaker cells o Heart cells that regularly produce spontaneous electrical impulses o Impulses spread throughout heart muscle cells and stimulates them to contract Control of Heart Rhythm atrial cells Sinoatrial SA Node primary pacemaker Gap junctions between cardiac muscle cells allow impulses to travel along Atrioventricular AV Node second pacemaker cell cluster Clicker Q Blood retuning to the mammalian heart in a pulmonary vein drains Figure 42 9 first into the left atrium Clicker Q If a molecule of CO2 released into the blood in your big toe travels out of your nose it must pass through all of the following structures except o Right atrium o Pulmonary vein o Alveolus o Right ventricle Concept 42 3 Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels Arteries thick walled vessels with smooth muscle and connective tissue to Arterioles branch off of arteries smaller in diameter help control the Blood Flow Away from the Heart withstand high pressure distribution of blood flow Figure 42 10 Blood Flow Toward the Heart Capillaries merge to form large venules Venules merge to form veins Veins Figure 42 10 o Contain smooth muscle and connective tissue o Thinner walled than arteries o Contain one way valves to prevent backflow o Skeletal muscle contractions compress veins and drive blood movement towards heart Figure 42 13 Clicker Q In the human systemic circuit blood will pass through all but which of the following Lungs pulmonary circuit goes to the lungs Capillaries Function o Two mechanisms regulate the distribution of blood to the capillaries The contraction of smooth muscle layer in the arterioles Precapillary sphincters regulate flow Capillary exchange of the capillaries o Exchange between blood and interstitial fluid takes place across walls o Blood pressure and osmotic pressure drives fluids out of capillaries at arteriole end and into capillaries at the venule end o Understand how this process works sequence of events o Figure 42 15 Blood Flow Velocity The velocity of blood flow varies in the circulatory system Slowest in the capillary beds because of large total cross sectional area o In sections with smaller cross sectional area aorta for ex the velocity of the blood is greater o Called continuity principle velocity of fluid changes based on cross sectional area Figure 42 11 Clicker Q Fluid moves back into the capillaries at the venous end of a capillary bed as a result of an osmotic pressure that is higher than the blood pressure Clicker Q T F The primary reason for the decrease in blood flow velocity in capillaries is increased resistance ie friction o False it s the continuity principle change in cross sectional area Concept 42 4 Blood Components Function in Exchange Transport and Defense Two Major Blood Components Plasma 55 o Fluid portion of blood o 55 60 of blood volume o About 90 water o Other components Hormones Nutrients Gases Salts Waste products ammonia urea Water soluble proteins Cellular components 45 o Erythrocytes red blood cells Contains hemoglobin Binds to O2 in lungs releases O2 in tissues o Leukocytes white blood cells Lymphocytes T Cells and B cells Phagocytes Monocytes and neutrophils o Platelets Derived from pieces of megakaryocytes Stem Cells and the Replacement of Cellular Elements Erythrocytes leukocytes and platelets all develop from a common source stem cells Multipotent stem cells in the red bone marrow Blood Clotting repair mechanism Damage to the endothelium of a blood vessel initiates the clotting mechanism Blood clot is formed from sticky fibrin protein threads platelets and other cells forming a patch over the wound site Understand this process know sequence of events Clicker Q When they are mature and circulating in the blood which of the following cellular elements of human blood have no nuclei Platelets and erythrocytes Concept 42 5 Gas Exchange Occurs Across Specialized Respiratory Surfaces Process supplies oxygen for cellular respiration and disposes of carbon dioxide Process o Take in oxygen through respiratory system o Oxygen gets transported to circulatory system o Circulatory system transports oxygen to cells o Oxygen is used in cellular respiration to make ATP o The CO2 produced is transported by the circulatory system back to the respiratory system where it is eliminated Common Features of Animal Respiratory Systems Respiratory surfaces must be moist so gases can diffuse across cell Cells lining respiratory surface are thin to optimize gas diffusion The respiratory surface area must be larger to allow for adequate gas membranes exchange Gills in Aquatic Animals Pros of living in water have to get oxygen from the water o Cells of respiratory surface are kept moist Cons of living in water o O2 concentrations are low in water o The warmer and saltier the water the less O2 Fish Gills Gas exchange is increased by ventilation and countercurrent exchange o Ventilation increase flow of medium over respiratory surface o
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