L26+water+nutrition+preview+5+apr+2010.ppt

In most animals, one or more transport epithelia spend energy to regulate solute and water movements to affect osmotic and ionic regulation and the often related function of metabolic waste removal fish gills vertebrate kidney Lungs or gills Homeostasis of water and electrolytes and excretion of nitrogenous waste involves passive exchange processes water barrier adaptations at body/environment interfaces - such as the integument, exoskeleton. behavioral adaptations energy-costing mechanisms of selective retention and removal of molecules across transport epithelia Osmoregulatory "cost" Osmoregulatory cost is dictated by the magnitude of the osmotic gradient? which reflects the amount of work required to pump solutes across membranes to achieve osmotic homeostasis In many animals, epithelial cells that transport sodium and chloride ions the involve the same combination of membrane proteins (pumps, cotransporters, channels) salt-excreting nasal glands of many marine birds and reptiles chloride cells on gills of marine bony fishes, and probably freshwater bony fishes renal tubules of the mammalian kidney In many animals, epithelial cells that transport sodium and chloride ions the involve the same combination of membrane proteins (pumps, cotransporters, channels) salt-excreting nasal glands of many marine birds and reptiles chloride cells on gills of marine bony fishes, and probably freshwater bony fishes renal tubules of the mammalian kidney shark rectal gland Shark Rectal Gland Rectal gland Rectal gland secretes NaCl Some water and electrolytes lost in urine Gain some water in food Lumen of rectal gland (higher Na+, Cl?) Gain some electrolytes in food Gill Gain metabolic water Rectal gland epithelium (lower Na+, Cl?) Seawater (higher Na+, Cl?) Gill epithelium (lower Na+, Cl?) Gain Na+, Cl? by diffusion Cartilaginous fish produce nontoxic TMAO from urea, retain it, making their body fluids isotonic to seawater ? and so do not lose water to the enironment by osmosis -- but they must still eliminate Na+ and Cl- Freshwater Fish Saltwater Fish Terrestrial Animals Kangaroo Rat Camel (Skin, respiratory epithelia) Kidney function Excretion is the process of eliminating metabolic waste Excretory systems also typically function in ionic and osmotic regulation Vertebrate Kidney Metanephros Functional kidney of adult reptiles, birds and mammals Mesonephros Functional kidney of adult lampreys, fishes, amphibians Vertebrate Kidney Abdominal cavity Colon Kidney Peritoneum Kidney, Homo sapiens The kidney has two distinct regions; an outer renal cortex and an inner renal medulla. Both regions are densely packed with microscopic excretory tubules and their associated blood vessels - nephrons The Vertebrate Kidney The basic functional unit of the vertebrate kidney is the nephron; The vertebrate nephron consists of a renal tubule closely associated with two capillary beds, the glomerulus and the peritubular capillaries The structure and function of nephrons in kidney tissue allows for significant water conservation; production of highly concentrated urine that is hypersomotic to the blood fluid it processes The Vertebrate Kidney The basic functional unit of the vertebrate kidney is the nephron; The vertebrate nephron consists of a renal tubule closely associated with two capillary beds, the glomerulus and the peritubular capillaries The structure and function of nephrons in kidney tissue allows for significant water conservation; production of highly concentrated urine that is hypersomotic to the blood fluid it processes Countercurrent exchangers Countercurrent exchangers transfer heat or compounds between opposing inflow and outflow using only passive processes. Counter Current Multipliers Counter Current Multipliers are like exchangers, but involve active transport mechanisms.