katyzzzKidney and working
August 29th 2006 21:52
kidney-nephron
kidneys are two bean-shaped organs, each about the size of your fist. They are located in the middle of your back, just below your rib cage, on either side of your spine. Your kidneys weigh about 0.5 percent of your total body weight. Although the kidneys are small organs by weight, they receive a huge amount -- 20 percent -- of the blood pumped by the heart. The large blood supply to your kidneys enables them to do the following tasks:
Regulate the composition of your blood
keep the concentrations of various ions and other important substances constant
keep the volume of water in your body constant
remove wastes from your body (urea, ammonia, drugs, toxic substances)
keep the acid/base concentration of your blood constant
Help regulate your blood pressure
Stimulate the making of red blood cells
Maintain your body's calcium levels
Your kidneys receive the blood from the renal artery, process it, return the processed blood to the body through the renal vein and remove the wastes and other unwanted substances in the urine. Urine flows from the kidneys through the ureters to the bladder. In the bladder, the urine is stored until it is excreted from the body through the urethra.
If you were to cut a kidney in half, you would see the following parts:
renal capsule - a thin, outer membrane that helps protect the kidney
medulla - a darker, reddish-brown, inner region
renal pelvis - a flat, funnel shaped cavity that collects the urine into the ureters.
Why You Urinate Soon After Drinking a Large Glass of Water :
When you drink a large glass of water, the water gets absorbed into the blood and the following happens:
The absorbed water increases the amount of water filtered in the glomerulus.
The absorbed water in the blood reduces the Na concentration a little.
The reduced Na concentration lowers the amount of Na filtered in the glomerulus.
The nephron reabsorbs all of the reduced Na load and some of the accompanying water, leaving excess water in the filtrate.
The reduced Na concentration is sensed by the osmoreceptors.
The osmoreceptors do not secrete as much ADH.
Because the collecting ducts do not see as much ADH, they do not allow much water to be reabsorbed in response to the Na concentration gradient set up by the loop of Henle.
The excess water gets excreted in the urine.
When the excess water is excreted, the Na concentration of the blood returns to normal.
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Comment by j-j-lynn
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