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Circulation in Animals

Circulation in Animals. All organisms exchange materials and energy with their environment Materials move across the cell membrane to cytoplasm and wastes move out of cell. Most animals have specialized organ systems to exchange materials with the environment.

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Circulation in Animals

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  1. Circulation in Animals • All organisms exchange materials and energy with their environment • Materials move across the cell membrane to cytoplasm and wastes move out of cell. • Most animals have specialized organ systems to exchange materials with the environment.

  2. Cnidarian Body PlanA gastrovascular cavity instead of a circulatory system

  3. Circulation in Animals • Hydra and other cnidarians do not have a circulatory system. • Their body wall only two cells thick • Have a central gastrovascular cavity used for digestion and diffusion of substances throughout body.

  4. Circulation in Animals • Animals with many cell layers diffusion is insufficient • Internal distances are too great. • Glucose diffuses 1 cm in three hours in a human • In more complex animals, two types of circulatory systems have evolved: • open circulatory systems • closed circulatory systems • Both have a circulatory fluid, a set of tubes, and a muscular pump (the heart). Heart circulates blood by applying pressure

  5. Open circulatory system - circulatory fluid not always in a vessel. Blood and fluid around cells (interstitial fluid) mix and called hemolymph • Found in arthropods and most mollusks • One or more hearts pump hemolymph into spaces around organs for exchange between hemolymph and body cells. • heart contracts hemolymph pumped out into body • heart relaxes, draws hemolymph into vessels

  6. Open Circulatory System

  7. Closed Circulatory System • In a closed circulatory system, blood is confined to vessels • Found in some invertebrates (earthworm, squid, octopus) and vertebrates

  8. Blood Vessels In a Closed System • Same: • layer of elastic connective tissue • smooth muscle • endothelium lining • Different: • Capillaries lack connective tissue and smooth muscle • Arteries have thicker smooth muscle layer • Veins have valves and skeletal muscle aids in blood circulation in veins

  9. Metabolic Rate and Evolution of Cardiovascular Systems. • In general, animals with high metabolic rates have more complex and powerful circulatory systems than animals with low metabolic rates. • From low to high metabolic rate compare closed circulatory systems of: • Fish • Amphibian • Crocodilians, Birds, and Mammals

  10. Fish Circulatory System • Blood pumped from ventricle to gills (picks upO2 and disposes of CO2) • The gill capillaries lead to a vessel that carriesoxygenated blood to body and then back to heart

  11. Fish Circulatory System • In fish, blood passes through two capillary beds, the gill capillaries and systemic capillaries. • When blood flows through a capillary bed, blood pressure (the force pushing circulation) decreases • Oxygen-rich blood leaving gills flows to systemic circulation slowly

  12. Amphibian Circulatory System • Three-chambered heart with two atria and one ventricle. • Has double circulation pulmocutaneous and systemic circulation.

  13. Amphibian Circulatory System • Advantage is vigorous blood flow to brain, muscles, and organs because blood pumped a second time after has lost pressure in capillaries • BUT some O2 poor blood mixes with O2 rich blood in ventricle

  14. Bird, Crocodilian and Mammal Circulatory System • Four chambered heart. • The left side receives and pumps O2 rich blood, while right side handles O2 poor blood. • Double circulation restores pressure to systemic circuit and prevents mixing of O2 rich and O2 poor blood.

  15. Comparative Anatomy of 3 Closed Circulatory Systems

  16. Human Heart

  17. Cardiac Cycle

  18. Control of the heart beat

  19. Blood Flow Velocity and Pressure • Blood velocity fastest in arteries, slows down in capillaries and speeds up a little in veins • Caused by large total cross sectional area of capillaries • Blood pressure (pressure blood exerts on vascular tissue) is highest in arteries

  20. Capillary Exchange • Exchange of substances between blood and interstitial fluid occurs in capillary bed • Exocytosis across endothelial cells • Diffusion across endothelial cells • Pressure differences force some materials out of clefts between adjoining endothelial cells

  21. Pressure Differences between Capillaries and Interstitial Fluid • At arteriole end of capillary net movement out because blood pressure is greater than osmotic pressure, and venule end of capillary net movement in because osmotic pressure is greater than blood pressure

  22. Lymphatic System • Not all fluid returned to blood at vein end of capillary bed • Net loss of 4 L of fluid a day • Fluid enters lymph capillaries that are embedded around blood capillaries • Fluid called lymph and similar to interstitial fluid • Lymph Vessels have valves, contract rhythmically to move fluid but also rely on voluntary muscle contractions

  23. Lymphatic System • Lymph nodes filter lymph and fight infection • Lymph returned to blood by a duct between the vena cava and right atrium

  24. Blood

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