Explain briefly,micturition and disorders of the excretory system.

(N/A) Micturition: The process of release of urine is called micturition. The urinary bladder stores urine until a voluntary signal is given by the $CNS$ (Central Nervous System). As the bladder fills,stretch receptors on its walls send signals to the $CNS$. The $CNS$ then sends motor messages to initiate the contraction of the smooth muscles of the bladder and the simultaneous relaxation of the urethral sphincter,causing the release of urine.
Disorders of the Excretory System:
$1$. Uremia: Presence of excessive urea in the blood,often caused by kidney malfunction or infection in the uriniferous tubules.
$2$. Renal Failure: Malfunctioning of the kidneys leading to the inability to excrete waste properly. It can be treated by hemodialysis,where an artificial kidney (haemodialyzer) filters the blood using a cellophane membrane and a dialyzing fluid.
$3$. Kidney Stones: Insoluble masses of crystallized salts (like oxalates) formed within the kidney,which can obstruct the urinary tract and cause acute pain.
$4$. Nephritis: Inflammation of the renal pelvis,interstitial tissues,and calyces,typically caused by bacterial infection. Symptoms include a burning sensation during urination,back pain,and increased frequency of urination.