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Describe the process of urine formation in the mammalian kidneys

Describe the process of urine formation in the mammalian kidneys

Answers

Kavungya
The afferent arteriole which is a branch of the renal artery supplies blood to the glomerulus;
the afferent arteriole has a wider lumen/diameter than the efferent arteriole; which takes away
blood from the glomerulus;the differences in the diameter of the afferent and the afferent
vessels causes high pressure; leading to ultrafiltration of blood; the walls of the blood
capillaries are one-cell thick; hence glucose, amino acids,vitamins, hormones, salts, creatine,
urea and water filter into the Bowmans capsule; to form glomerular filtrate;

White blood cells, red blood cells, plasma proteins such as globulin and platelets are too large
to pass through the capillary wall; hence remain in the blood capillaries; useful substances in
the human body are selectively reabsorbed; back into the blood stream at the proximal
convoluted tubule; the tubule is highly coiled; to increase the surface area for reabsorption of
the substances; the useful substances include amino acids,glucose, vitamins, hormones, sodium
chloride and water;

Many mitochondria found at the proximal convoluted tubule; provide energy for reabsorption
of these substances against a concentration gradient; the glomerular filtrate flows into the
descending and the ascending limb of the loop of Henle; blood in the capillaries and the
glomerular filtrate in the loop of Henle move in opposite directions/counter-current flow; this
provides a steep concentration gradient that leads to maximum absorption of water through
osmosis;

Sodium chloride is actively absorbed from the ascending limb into the blood capillaries; under
the influence of aldosterone hormone; the glomerular filtrate flows into the collecting tubule
from where, more water is reabsorbed into the blood stream; antidiuretic hormone influences
the amount of water to be reabsorbed depending on the osmotic pressure of the blood; the
glomerular filtrate from several collecting tubules now referred to as urine; is emptied into the
collecting duct;

The urine passes through pyramid, pelvis and ureter into the bladder; where it is stored for
some time. The sphincter on the urethra relaxes to allow urine to be released from the body;
Kavungya answered the question on May 13, 2021 at 13:12

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