Micturition (Urination)
Micturition is emptying urinary bladder.
Expulsion of urine from urinary bladder.
About 150 -180 liter of water filters though glomeruli each day, but only 1.5 liter is excreted in urine, about 99% is reabsorbed.
Micturition is initiated by following events-
Urinary bladder act as reservoir of urine.
When 300-400ml of urine has accumulated in bladder.
The autonomic nerve fibers which are present in wall of bladder are stimulated.
When these impulse or nerve fibers are stimulated, these fibers will send message or impulse to the brain through spinal cord.
After this, with the help of these nerve fiber contraction of the muscles starts in bladder.
Due to this contraction the internal Urethral sphincter relax, which will lead to passage of urine or micturition.
When urination is complete, internal Urethral sphincter contract.
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