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Osmoregulation And Excretion In Animals

Osmoregulation And Excretion In Animals

 

 

 

General Points on Kidney:

 

Elasmobranchs can retain 2.5% of urea in their body fluids to make them hyperosmatic to counter the highly concentrated sea water. For this, these have urea absorbing segments in their nephrons.

 

  • Bidder’s canal : Inside the kidney of male frog and carries the sperms only.
  • Contractile vacuole is absent in marine and parasitic protozoans as these are found in isotonic media.
  • All the flat worms e.g. planarians, flukes and tape worms have protonephridia (Flame cells or solenocytes) for excretion and osmoregulation. Each flame cell has a bundle of cilia whose beating gives the appearance of flickering of a candle flame.
  • Fresh-water fishes have large glomeruli to expel excess water so urine is highly hypotonic, while marine bony fishes are either aglomerular or have small glomeruli and expel small amount of isotonic urine.
  • Marine bony fishes have salt secreting cells in their nasal chambers and gills.
  • Gout : Excess of uric acid is deposited in the joints (especially those of great toes) and causes painful movements and arthritis.
  • Ornithinic acid : Nitrogenous excretory waste of certain birds.
  • In human urine, uric acid is mainly formed from the purines of nucleic acids.
  • Rennet cell : Excretory cell of Ascaris.
  • Septal nephridia and Pharyngeal nephridia of earthworm are enteronephric as they release wastes in gut.
  • Neural gland : Excretory structure of Urochordates e.g. Herdmania.
  • Guanin is the nitrogenous waste of many spiders, so called guanotelic.
  • Study of structure, working and disorders of kidneys is called nephrology while study of female urinary tract and male urinogenital tract is called urology.
  • Urography : Radio x-ray photograph of urinary tract.
  • Urinometer : Instrument used to measure specific gravity of urine.
  • Hepatic vein is with maximum amount of urea, while renal vein is with minimum amount of urea.
  • Incomplete loop of Henle is found in birds while complete loop of Henle is found in mammals. There is no loop of Henle in nephrons of fishes, amphibians and reptiles.
  • Urinary bladder is absent in cyclostomes, cartilage fishes, snakes, alligators, crocodiles and birds.
  • Sweating is mainly meant for cooling of body and not for excretion.
  • Urate cells : Excretory cells of fat body of insects. These store the nitrogenous wastes permanently called excretion by storage.
  • In lower animals, ammonia is formed in all the cells.
  • Desert mammals have long loop of Henle for more conservation of water.

 

 

 

Sub Topics of Osmoregulation And Excretion In Animals

 


 

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