Due to various metabolic activities various nitrogenous waste are produced in our body.

It is necessary to remove this wastes from our body in order to keep ourselves healthy.

Elimination of this nitrogenous wastes is known as Excretion.


Salts,water vapour,urea,uric acid, ammonia,urine etc.



Liver,Lungs(Co2 and water),Kidneys,Ureters,Urinary bladder,and Urethra.


Kidneys are brown,bean shaped.With a notch(hilus) coming out through which the waste is tranfered to the ureter.Each kidney has nephrons which are the structural and functional unit and each kidney consist of 10 lakhs of nephrons so in a body there are approxiametly 20 lakhs nephrons.

* Kidneys are called main excretory organ because large amount of waste is released by kidneys.


This are 20 to 25 cm in size.Through which the urine is transported to the urinary bladder.Ureters are thin walled.


The bladder stores the urine temporalily and then sends to the urethra.


This is the organ through which the urine eliminates from the body. Urethra is longer in males than females because it serves as a passage for semen.In males it is 20 cm and in females it is 4 cm approximetly.


The outer surface of kidney is called the cortex and the inner surface is termed as medulla.In medulla there are 7 to 8 triangular structures known as pyramids in which the nephrons are present.These structures include the vasa rectae (both spuria and vera), the venulae rectae, the medullary capillary plexus, the loop of Henle, and the collecting tubule.The renal medulla is hypertonic to the filtrate in the nephron and aids in the reabsorption of water.

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