Osmoregulation in man especially the loss of water is also carried out through sweating by skin and expiration or exhalation by the lungs.
[2] Excretion:- The kidney is also involved in the removal of metabolic waste product from the body in form of urine. The process involved in the formation of urine occurs in these phases which are [1] ultra- filtration [2] selective reabsorbtion and [3] hormonal secretion.
Blood is brought to the kidney by renal artery. As it circulate through the capillaries or glomerulus of each bowmans capsule, water, urea, nitrogenous compoubd, minerals salt, sugar, glucose and plasma solute are filtered into the capsule . This process of filtering materials from the glomerus into the bowman capsule is called ultra fitration.
The fluid in the capsule or glumerular filtrate now flows down the tubule. At the proximal convoluted tubule and henle loop some water, sugar, amino acids and salt which are useful to the body are reabsorbed into the blood capillaries against concentration gradient by active transport. This process of reabsorbing useful materials back into the blood is called selective reabsorbtion.
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The fluid in the tubule become more concentrated as it flows through the distal tubule where more water is reabsorb by the action of Anti-diuretic hormone [ADH] and urine is finally formed.
The urine gradually trickles into the renal pelvis and is propelled by peristalsis through the ureter into the urinary bladder. When the bladder is full, it contract, discharging the urine out of the body through the urethra.