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

Videos and Websites

http://www.biologymad.com/resources/kidney.swf

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 CO2 and diluted in water to form urine, produced by some terrestrial animals