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| Summary |
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| Excretion |
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| The removal of harmful and unwanted toxic waste products of metabolism is known as excretion. |
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| Osmoregulation |
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| The process by which the water content and the ion concentration is regulated and kept constant in the cell is known as osmoregulation. |
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| Excretory wastes |
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| This consists of respiratory wastes, nitrogenous wastes and bile pigments. |
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 Nitrogenous wastes consists of ammonia, urea, uric acid and amino acids. |
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Excretion and osmoregulation takes place in the amoeba through the contractile vacuole. |
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Excretion and osmoregulation takes place in the earthworm through the nephridia and skin. |
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Excretion and osmoregulation in man takes place through the kidneys. Excretion also takes place through the skin, lungs and liver. |
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The urinary system in man consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. |
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Each kidney has three distinct regions, cortex, medulla and pelvis. |
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The nephron is the structural and functional unit of the kidney. |
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Each nephron has a network of capillaries called glomerulus which fits into a cup called the Bowman's capsule and a long tubule consisting of proximal convoluted tubule, Henle's loop, distal convoluted tubule and connecting tubule. |
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| Urine is formed in three steps: |
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Glomerular filtration |
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Selective reabsorption and |
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Tubular secretion |
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| Kidney is excretory and also osmoregulatory in function. |
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