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Excretory System. For Unicellular Organisms. It’s easy! Every cell is in direct contact with the external environment – so wastes are released directly from the cell. For multicellular Organisms. More complicated Not every cell is in direct contact with the external environment
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For Unicellular Organisms... • It’s easy! • Every cell is in direct contact with the external environment – so wastes are released directly from the cell
For multicellular Organisms... • More complicated • Not every cell is in direct contact with the external environment • Wastes must be collected and stored because not every cell is designed to remove them!
For multicellular Organisms... • produce more wastes • Have specialized cells that allow for more efficient waste removal
Excretion • The process of separating wastes from body fluids • Eliminating wastes from the body • Involves many body systems
What type of wastes? • CO2 produced during CR (and water vapour) The RESPIRATORY SYSTEM
What type of wastes? • Water, salts, and some urea in perspiration The INTEGUMENTARY SYSTEM (Your Skin!)
What type of wastes? • Water, salts, lipids, and a variety of cellular chemicals The DIGESTIVE SYSTEM
What type of wastes? • NOTE: Elimination of food residue (i.e. In feces) is NOT considered to be excretion Why?
AKA the Urinary System The Excretory System
Functions Excretion of Metabolic Wastes • performed by the kidneys • includes nitrogen-containing wastes (ammonia, urea, uric acid)
Functions Maintenance of Water-Salt Balance • performed by the kidneys • keeps appropriate balance of water and salt in the blood (involved in regulating blood pressure)
Functions Maintenance of Acid-Base Balance • performed by the kidneys • regulate acid-base balance in blood by excreting H+ and reabsorbing HCO3- (as needed)
Functions Secretion of Hormones • performed by the kidneys • kidneys secrete calcitriol, erythropoietin, renin What do these hormones do? Read pg 445