BIOL 212 Circulation and Gas Exchange-1.pptx

Circulation and Gas Exchange 1  Circulation and Gas Exchange I. Circulatory Systems II. Vertebrate Circulation III. Circulatory Fluids IV. Respiratory Adaptations V. Breathing 2  Learning Objectives 1. List the compon...

Circulation and Gas Exchange 1  Circulation and Gas Exchange I. Circulatory Systems II. Vertebrate Circulation III. Circulatory Fluids IV. Respiratory Adaptations V. Breathing 2  Learning Objectives 1. List the components of a circulatory system 2. Describe the multi-purpose nature of a gastrovascular cavity 3. Compare the components and effectiveness of open and closed circulatory systems 4. Identify the main animal clades showing open circulation and those with closed circulation 5. Compare the circulatory systems of vertebrates 3  Learning Objectives 6. Compare the composition of hemolymph and blood 7. Explain the meaning of respiratory medium 8. Describe the respiratory surfaces of animals 9. Evaluate the roles of the respiratory pigments of animals 10. Describe the breathing mechanisms in amphibians, birds 4  I. Circulatory Systems A. Circulation in Animals Diffusion time is proportional to the distance squared Diffusion is only efficient over small distances In small and/or thin animals, cells can exchange materials directly with the surrounding medium In most animals, cells exchange materials with the environment via a fluid-filled circulatory system 5 B. Properties of circulatory systems 1. A circulatory system minimizes the diffusion distance in animals with many cell layers 2. A true circulatory system has a) A circulatory fluid b) A set of interconnecting vessels c) A muscular pump, the heart 3. The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes 4. Circulatory systems can be open or closed, and vary in the number of circuits in the body 6 C. Gastrovascular Cavities 1. Some animals lack a circulatory system 2. Some cnidarians, such as jellies, have elaborate gastrovascular cavities 3. A gastrovascular cavity functions in both digestion and distribution of substances throughout the body 4. The body wall that encloses the gastrovascular cavity is only two cells thick 5. Flatworms have a gastrovascular cavity and a large surface area to volume ratio 7 D. Open Circulation 1. In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system 2. In an open circulatory system, there is no distinction between blood and interstitial fluid, and this general body fluid is called hemolymph 8 E. Closed Circulation a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid Closed systems are more efficient at transporting circulatory fluids to tissues and cells Annelids, cephalopods, and vertebrates have closed circulatory systems 9 F. Cardiovascular System In humans and other vertebrates Arteries branch into arterioles and carry blood away from the heart to capillaries Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid Venules converge into veins and return blood from capillaries to the heart Arteries and veins are distinguished by the direction of blood flow, not by O2 content Vertebrate hearts contain two or 10  II. Vertebrate Circulation A. Single Circulation Bony fishes, rays, and sharks have single circulation with a two-chambered heart In single circulation, blood leaving the heart passes through two capillary beds before returning 11 B. Double Circulation Amphibian, reptiles, and mammals have double circulation Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart 12 C. Amphibian Circulation 1. Frogs and other amphibians have a three-chambered heart: two atria and one ventricle 2. The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit 3. When underwater, blood flow to the lungs is nearly shut off 13 D. Reptilian Circulation Turtles, snakes, and lizards have a four-chambered heart: two atria and two ventricles with an incomplete septum In alligators, caimans, and other crocodilians the septum is complete Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit 14 E. Mammalian and Avian Circulation 1. Mammals and birds have a four-chambered heart with two atria and two ventricles 2. An interventricular septum divides the two atria 3. The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood 4. Mammals and birds are endotherms and require more O2 than ectotherms 15 F. Mammalian Circulation 1. Blood begins its flow with the right ventricle pumping blood to the lungs 2. In the lungs, the blood loads O2 and unloads CO2 3. Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped through the aorta to the body tissues by the left ventricle 4. The aorta provides blood to the heart through the coronary arteries 5. Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs) 6. The superior vena cava and inferior vena cava flow into the right atrium 16  III. Circulatory Fluids A. Body fluids can be categorized as 1. Intracellular: The cell’s cytosol (70- 90% water) 2. Extracellular: Blood, plasma, and interstitial fluid. 17 B. Plasma and Interstitial Fluid Composition. 1. About 90% water 2. There is more protein in plasma than in interstitial fluid 3. Interstitial fluid returns to the circulatory system as lymph 4. Both deliver water, ions and nutrients to body cells. 18 C. Blood composition. 1. Plasma (55%), and cellular elements (45%) 2. Erythrocytes: transport oxygen 3. Leukocytes: Defense and immunity 4. Platelets: Blood clotting 19 D. Hemolymph (the same as interstitial fluid). 1. Circulates in the body of molluscs and arthropods (open circulation). 2. Composed of water, ions (mostly Na+, Cl-, K+, Mg+, and Ca+), proteins, carbohydrates and lipids. 3. Amoeboid cells (hemocytes) aid with immune defense. 20 E. Hemostasis: preventing blood loss. 1. Platelets concentrate around breakage 2. Clotting factors change prothrombin to thrombin. 3. Thrombin turns fibrinogen to fibrin. 4. A blood clot of interwoven platelets, blood cells and fibrin forms. 21  IV. Respiratory Adaptations A. Breathing 1. The exchange of gasses between the animal and its surrounding environment. 2. Animals take up oxygen and release carbon dioxide. 3. This requires the collaboration of circulatory and respiratory systems. 22 B. The respiratory medium is the source of oxygen for the animal: 1. Air (21% oxygen) 2. Water (Dissolved oxygen, less than 0.015%) C. The respiratory surface is the animal structure that exchanges gasses with the respiratory medium (gills, trachea, lungs, skin ). D. Respiratory pigments transport oxygen throughout the animal’s body: 1. Hemocyanin in mollusks and arthropods 2. Hemoglobin in vertebrates and annelids 3. Myoglobin in mammalian muscle cells stores additional oxygen 23 E. Cutaneous breathing 1. Also known as integumentary exchange. 2. Common in animals that live in water or moist environments. 3. Gas difuses through the skin into body fluids or capillary networks. 4. Seen in cnidarians, worms, and some vertebrates such as fish and amphibians. 24 F. Gills. 1. The respiratory surface used by aquatic animals. 2. Gas exchange is optimized by - Increased surface area - Ventilation (increasing water flow over gills) - Countercurrent exchange (blood flows opposite to water flow) 25 26 G. Trachea. 1. Used by insects. 2. Trachea are larger tubes that open to the outside. 3. Tracheoles are smaller tubules that move air from trachea to organs and tissues 27 H. Lungs. 1. Typical of vertebrates 2. Requires air flow by ventilation 3. Air passes through trachea, bronchi, and bronchioles 4. Gas is exchanged in the alveoli 5. Surfactant liquid keeps alveoli lining moist 28  V. Vertebrate Breathing The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air A. An amphibian such as a frog ventilates its lungs by positive pressure 29 B. Bird Breathing Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs Air passes through the lungs in one direction only Every exhalation completely renews the air in the lungs 30 C. Mammalian Breathing 1. Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs 2. Lung volume increases as the rib muscles and diaphragm contract 3. The tidal volume is the volume of air inhaled with each breath 4. The maximum tidal volume is the vital capacity 5. After exhalation, a residual volume of air remains in the lungs 31