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Circulation and Gas Exchange

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  1. Circulation and Gas Exchange Circulation in Animals Gas Exchange in Animals

  2. 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

  3. 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

  4. Gill capillaries Lung and skin capillaries Lung capillaries Lung capillaries AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS FISHES Right systemicaorta Pulmonarycircuit Artery Pulmocutaneouscircuit Pulmonarycircuit Gillcirculation Heart:ventricle (V) Left Systemicaorta A A A A A A Atrium (A) V V V V V Left Right Left Left Right Right Systemiccirculation Systemic circuit Systemic circuit Vein Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries

  5. 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

  6. 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

  7. Plasma Water-90% Electrolytes-inorganic salts Proteins-immunoglobulins, 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 Blood: Plasma and Cells

  8. 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

  9. 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

  10. 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%) Oxygen and Carbon Dioxide Transport