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Circulation and Gas Exchange Circulation in Animals Gas Exchange in Animals Circulation in Animals Transport systems necessary to connect body parts with organs of exchange Critical component to maintaining homeostasis Gastrovascular cavity in flatworms and cnidarians Open vs. closed systems Cardiovascular systems accommodate gills and lungs Evolution of the Heart • Fish: two chambers, one atrium, one ventricle • Amphibians: larval stage-two chambers adult stage-three chambers, two atria, one ventricle • Reptiles: three chambers, most partially divided ventricle • Birds and Mammals: four chambers, two of each, complete separation of oxygenated and deoxygenated blood AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS Lung and skin capillaries Lung capillaries Lung capillaries FISHES Gill capillaries Artery Pulmocutaneous circuit Gill circulation Heart: ventricle (V) A Atrium (A) Systemic circulation Vein Systemic capillaries A V Left Right Systemic circuit Systemic capillaries Right systemic aorta Pulmonary circuit A V Right Pulmonary circuit Left Systemic aorta V Left A Systemic capillaries A V Right A V Left Systemic circuit Systemic capillaries Arteries, Veins, and Capillaries • Arteries-blood away from the heart, smooth muscles, diameter able to be regulated • Veins-blood back to the heart, little elasticity, contain valves • Capillaries-functional unit of the circulatory system, all exchanges occur within the capillaries, arterioles, and venules Blood Pressure • Hydostatic force that the blood exerts against vessel wall • Greatest in arteries • Responsible for movement of fluid (plasma) out of the capillaries (arterioles), returns in venules (osmosis and diffusion) • Lowest in veins Blood: Plasma and Cells Plasma • Water-90% • Electrolytes-inorganic salts • Proteinsimmunoglobulins, fibrinogens • Nutrients, metabolic wastes, respiratory gases, and hormones Cellular elements-produced by pluripotent stem cells • Erythrocytes-red blood cells (RBC), oxygen transport, lack nuclei, mitochondria, 3-4 months • Platelets-blood clotting, cell fragments • Leucocytes-white blood cells, immunity Gas Exchange in Animals • O2 and CO2 exchange between animal and environment • Air or dissolved in water is the source of O2 • Respiratory surface: large, moist, permeable, vascularized • Body surface, gills, lungs, tracheal systems • Countercurrent exchange Mammalian Lungs • Alveolus-functional unit • Exchange is through diffusion, dependent upon partial pressure of O2 and CO2 • POO2= 160 mm Hg • POCO2=0.23 mm Hg Oxygen and Carbon Dioxide Transport Oxygen Transport • Utilizes respiratory pigments: hemocyanin in some invertebrates, hemoglobin in most vertebrates • Hemoglobin exhibits cooperativity • Hb affinity for O2 altered by pH (Bohr Shift) CO2 Transport • Transported in three forms: 1. Dissolved in plasma (7%) 2. Bound to Hb (23%) 3. Bicarbonate ion in the plasma (70%)