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Question
Describe the mechanism of urine formation in human excretory system. Draw a labelled diagram to illustrate your answer.
Solution
Kidneys are the main excretory organ of the human body. There are about millions of nephron in each kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, enclosed by a capsule called Bowman's capsule. The blood containing wastes (like urea) enters the glomerulus. The glomerulus filters the blood. During filtration, the filtrate (containing substances like glucose, amino acids, salts, water and urea) present in the blood travels through the renal tubule where materials needed by the body are reabsorbed, while the wastes like urea are collected and excreted in the urine. The nephron carries the urine into the collecting tubule of the kidney from where it is carried to the ureter. From the ureter, the urine passes into the urinary bladder. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.
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