18 osmoregulation 118

18 osmoregulation 118 - Biology 118 15. OSMOREGULATION...

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Biology 118 15. OSMOREGULATION OSMOTIC BALANCE: the body’s cells and tissues must maintain a precise concentration of electrolytes (ions). Too much water, or too little, will throw the balance and make trouble for cells, tissues and whole animals. WATER LOSS : can occur in various ways. Through the permeability of the skin. (Sweat) Through respiration. (Breathing) Through waste disposal. (Wastes eliminated from digestive tract and through the kidneys can take water with along it.) THE KIDNEY : this organ is specialized to filter the blood, removing wastes like urea, but returning water, ions and nutrients to the blood. The main strategy : to remove everything from the blood (except for blood cells and other large items), then selectively take back certain materials (like nutrients and ions and water). What’s left behind is the waste, (or any excess water or ions) which is eliminated as urine. The steps to achieve this are: Filtration reabsorption secretion excretion The nephron : this is the functional unit of the kidney (each kidney has about a million of them). Each nephron is a thin, hollow tube closely associated with capillaries. The tube is the transport epithelium – a sheet of cells that faces the environment. Renal corpuscle
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18 osmoregulation 118 - Biology 118 15. OSMOREGULATION...

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