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Human Excretory System - Biology Notes for SSC EXAM


Dear Readers,
Excretory system is one of the important topics of Biology for General Awareness Section of SSC CGL & CPO Exams. Every year 1-2 questions are expected from this section. Thus, the post is very helpful for the upcoming SSC Exams 2017. 

Excretory System: An  Inrtroduction

Excretion system: excretory system is the process by which an organism gets rid of waste products of its metabolism. The three terms excretion, secretion and egestion all describe the passing out of substances from organisms or cells. Removal of nitrogenous substances like urea, ammonia, uric acid etc. formed during metabolism from the body of human is called excretion.

Various animals and their excretory organs
Animals  Excretory organs
Unicellular animas Diffusion/Osmosis
Coelenterates Direct by cells
Plathyhelminthes Flame cells
Ascehehelminthes Renette cells
Annelida Nephridia
Porifera Canal system
Earth worm Chloragogan cell


The main excretory organs of human are as follows –

(i) Kidneys: kidneys are most vital and prominent organ in excretory system. Excretory process is mostly done by kidneys.
  • In human being there exist a pair of kidney which are dark-red, bean shaped.
  • Its weight is 140 grams.
  • There are two parts of it. Outer part is called cortex and the inner part is called medulla.
  • A kidney has about ten lakh structural and functional units, calleds as nephrons.
  • Bowman's capsule is a cup like structure in every nephron called.
  • Glomerulus of thin blood vessels are  found in the Bowman's capsule which is made up of two types of arterioles.
(a) Afferent arteriole: An afferent arteriole connects the renal artery to the glomerular capillary network in  kidney's nephron, Which carries the blood to the glomerulus, starting the filtering process.
(b) Efferent arteriole: it has less diameter than afferent arteriole and takes blood out of the glomerulus.

Functions of kidney:

  • It maintains PH of blood.
  • Ultra filtration – it is the process of filtration of liquids into the cavity of Bowman's capsule.
  • It maintains salt contents of body.
  • It eliminates toxic substances of body.
  • Homeostasis – kidney removes various unwanted materials from the blood, it helps in keeping the internal environment of the body constant.
  • Kidney secrets an enzyme Renin which change the plasma protein, the angiotensinogen.
(ii) Skin: Oil gland and sweat glands secrete sebum and sweat respectively. Along with sebum and sweat some other excretory substance to enhance excretory process.
(iii) Liver: the cells of the liver transform the excessive amino acids and ammonia of the blood into the urea which is the main excretory substance. And spleen split the damaged blood cells and separate them from the blood flow.
(iv) Lungs: in general Lungs are associated with respiratory system but it also plays an important role in excretory system. Lungs does the excretion of gaseous substance. CO2 and water vapours and some substances like garlic, onion and some species are also excreted by lungs.

Different excretory Products

List of various excretory products are as follow-
  • Nitrogenous waste material
  • Mineral salts
  • Co2
  • Water
  • Pigments
  • Creatine and creatinine
  • Vitamins and Harmones

All the Best!
Team AIMSUCCES
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