Excretory System - Notes, Biology, IAS UPSC Notes | EduRev

General Science(Prelims) by IRS Divey Sethi

UPSC : Excretory System - Notes, Biology, IAS UPSC Notes | EduRev

The document Excretory System - Notes, Biology, IAS UPSC Notes | EduRev is a part of the UPSC Course General Science(Prelims) by IRS Divey Sethi.
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Excretory System

 

Removal of waste from the body

Biology,IAS,UPSC,Exam Preparation

 

  • Waste materials excreted in animals are of many kinds :
  • Nitrogenous Substances, Carbon-Dioxide, Pigments, Excess Water, etc.

The Nitrogenous Waste can be excreted in the following forms :

  • Ammonia : Highly Toxic, Soluble in Water and has to be immediately excreted.
  • Urea : Far less toxic than ammonia. Less water required than ammonia. In Mammals, Alligators, Turtles (called Ureotelic).
  • Uric Acid : In animals where conservation of water is needed. In Birds, Insects, Land Reptiles (called Uricotelic).

Excretory System of Mammals

Kidneys

  • Left kidney is higher than the right kidney.
  • A kidney is composed of 1.2 million microscopic structural and functional units called nephrons or uriniferous tubules.

Ureters

  • Open into Urinary Bladder

Biology,IAS,UPSC,Exam Preparation

Urinary Bladder

  • Size depends upon the amount of urine in it (up to 700 – 800 ml).
  • The lower part is guarded by 2 Sphinctors : inner involuntary and outer voluntary.

Urethra

  • Leads to the exterior.
  • In females, it carries only urine. Opens by urinary aperture in the vulva in front of vaginal aperture.
  • In males it carries urine as well as spermatic fluid.

Nephron

Biology,IAS,UPSC,Exam Preparation

Functional unit of kidney.

  • It is a long tube differentiated into 4 regions.
  • 1. Bowman’s Capsule
  • 2. Proximal Convoluted Tubule (PCT)
  • 3. Loop of Henle
  • 4. Distal Convoluted Tubule (DCT)

Biology,IAS,UPSC,Exam Preparation

 

1. Bowman’s Capsule

  • Contains a globular bunch of capillaries, the glomerulus.
  • The Bowman’s capsule and the glomerulus together form a globular body called Malpighian body.
  • In glomerular filtrate : water (99%), inorganic salts, amino acids, fatty acids, glucose, urea, uric acid, hippuric acid, hormones, vitamins are present.

2. Proximal Convoluted Tubule (PCT)

  • Starts from the neck of Bowman’s capsule and is highly twisted.
  • Almost whole of the glucose and vitamins, about 75% of amino acids, about 70% of Na and K, a large amount of Ca and Mg and 75% water is absorbed.

3. Loop of Henle

  • U – shaped.
  • Consist of 2 straight limbs : descending and ascending.
  • No water is absorbed in ascending limb.

4. Distal Convoluted Tubule (DCT)

  • Greatly twisted.
  • Reabsorbs some Na and Cl.
  • Leads to Collecting Tubules which lead to ureters

 

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