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Urine formation is the process that takes place in the kidney. The kidney receives blood from the renal artery. The renal artery branches into afferent arteriole that enters the glomerus. At the glomerulus, ultrafiltration occurs. In this process, the fluid part of blood (dissolved nutrients, some blood proteins,water,amino acids, urea) is forced out into the Bowman's capsule. The molecules which are large in size are not forced out; these include blood cells and blood proteins. The ultrafiltration is achieved due to pressure exerted at the glomerulus due to the afferent being wider than efferent.
The fluid that is forced out becomes glomerulus filtrate which flows down the nephron as reabsorption of useful nutrients occurs at different parts of the kidney.
At the Proximal convoluted tubule, glucose, some amount of water, amino acids and some vitamins are reabsorbed to the bloodstream.
At the Loop of Henle, mineral salts and ions usually sodium ions are reabsorbed by the help of Aldosterone hormone.The amount of sodium ions absorbed depends on the current need of the body. At the distal convoluted tubule,some amount of water is reabsorbed depending on the current need of the body. Of the osmotic pressure of blood is high (less water in the blood), more Antiduretic hormone is secreted by the pituitary gland. Antiduretic hormone increases permeability of the kidney tubules hence more water is reabsorbed leading to less concentrated urine. When blood osmotic pressure is low, less antiduretic hormone is secreted,permeability of kidney tubules decreases hence more amount and less concentrated urine is secreted.
After distal convoluted tubule, the excess water,some amount of salts and Urea from other nephrons collects at the collecting tubule, and then moved to the urinary bladder for temporary storage through the Ureter.
Biokenya answered the question on December 5, 2017 at 18:50
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