Osmoregulation and Excretion Water Balance and Waste Disposal Excretory Systems

Water Balance Osmoconformers-isoosmotic with their environment, most marine invertebrates Osmoregulators-regulate internal osmolarity by releasing or taking in water, many marine animals, all freshwater animals, terrestrials animals, and humans

Marine vs Freshwater Fish Marine fish remove salt through specialized glands and the kidneys, also drink large amounts of seawater Freshwater fish excrete large amounts of very dilute urine, use gills to take in Na+ and Cl- ions

Excretory Systems Functional similarities of all excretory systems Filtration of body fluids modification of that filtrate by: selective secretion of solutes and selective reabsorption of some of those solutes

Functional Unit of the Excretory System of Mammals-Nephron Kidney made of nephrons nephron-single long tubule and associated capillaries three processes occur: filtration, secretion, and reabsorption

Filtration Blood pressure within the glomerulus forces filtrate contains a mixture of glucose, salts, vitamins, nitrogenous wastes, and other small molecules

Secretion Plasma solutes are added to the filtrate highly selective, involves passive and active transport example: H+ ions helps maintain pH of body fluids

Reabsorption Selective transport of filtrate substances back into the interstitial fluid reclaims small essential molecules nearly all sugar, vitamins, organic nutrients reabsorbed, also some water

Regulation of Kidney Function ADH-antidiuretic hormone, enhances fluid retention by increasing the water permeability of the tubules, produced by hypothalamus, but released from the posterior pituitary RAAS-renin-angioltensin-aldoserone system cooperates with ADH and is opposed by ANF

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Excretory Products Ammonia is a byproduct of amino acid respiration it must be removed or converted to a less toxic form Ammonia is excreted through the gills and body surfaces of most marine and freshwater animals. Uric Acid- insoluble non toxic form produced by birds, reptiles, and other terrestrial forms Urea-ammonia is combined with CO 2 and diluted in water to form urine, produced by some terrestrial animals