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Excretory Products and their Elimination — BIOLOGY STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceBIOLOGYExcretory Products and their Elimination3 Marks
Question
Explain the mechanism of urine formation.
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Answer

  1. Glomerular Filtration:
  • A protein-free fluid is filtered from the blood of glomerular capillaries into the lumen of Bowman's capsule.
  • About 1200 ml of blood is filtered by the kidneys, per minute.
  • The glomerular filtration rate is about 125 ml/ minute or 180 litres/ day in a healthy human individual.
  1. Reabsorption:
  • Nearly 99% of the filtrate is reabsorbed in the renal tubule by the brush-bordered epithelial cells lining the renal tubule.
  • Certain substances like glucose, amino acids, Na+ ions, Ca+ ions and K+ ions are reabsorbed actively; nitrogenous wastes are reabsorbed passively and water by osmosis.
  1. Tubular Secretion:
  • - It is the process in which certain substances/ ions like K+, H+, and ammonia are directly secreted into the lumen of the nephron.

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