EXCRETORY SYSTEM -BIOLOGY- TNPSC,TET,RRB,SSC SCIENCE (GK) STUDY MATERIAL

EXCRETORY SYSTEM

  • Nitrogenous substances carbondioxide, pigments, excess water, etc.
  • The nitrogenous waste can be excreted in the following forms:
  • Ammonia, Urea, Uric acid- conservation of water is needed. 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 uriniferoustubules.
    Urethra
    Act of passing urine is called Micturition.
    EXCRETORY PRODUCTS
    AmmonotelicAnimals
    * These animal excrete nitrogen in the form of ammonia, e.g., aquatic invertebrates Amoeba, Hydra, Prawn, Pila, and freshwater fishes Bony Fish, Frog’s tadpole. Ureotelic Animals
    *They excrete nitrogen in the form of urea, e.g., mammal (man), frogs, toads, other amphibians and cartilaginous fishes like sharks.
    Uricotelic Animals
    * They excrete the nitrogenous wastes in the form of uric acid e.g., reptiles, snakes, lizards, crocodiles and birds.
    NEPHRON
    Functional unit of kidney. It is a long tube differentiated into 4 regions.
  • Bowman’s Capsule
    The Bowman’s capsule and the glomerulus together
    form a globular body called Malpighian body.
    * The yellow colourof urine is caused by the
    pigment urochrome, which is a breakdown
    product of haemoglobinfrom worn out RBCs
    * The urine on standing gives a pungent smell.
    It is due to conversion of urea into ammonia
    by bacteria
    * pH of urine is between 5-8. Average pH is
    6.0 (slightly acidic)
    * kidney stones: Calcium Oxalate.
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