"But now hath God set the members every one of them in the body, as it hath pleased Him." 1 Cor. 12:18.
Most of us have two kidneys. They are reddish-brown and are shaped like huge kidney beans. Kidneys are the most important waste-disposal part of the body. Through them our blood is continuously filtered to remove wastes and to help keep the chemical content of the blood in balance.
The Creator wisely gave us two of these important organs so that if one is severely damaged the other can carry on. Surely "His ways [are] past finding out." Rom. 11:33. Life could go on even if the one remaining kidney were also partially damaged, especially if the person's diet were carefully watched. But the normal, healthy kidneys are wonderful safeguards to our health, helping, among other things, to control our weight and blood pressure. Also, if we unwisely take in too much salt or sugar, the kidneys will get rid of the excess. However, there is a limit to this, and a wise person will avoid eating too much of these items.
The function of the kidneys is very complicated. Each kidney acts separately, extracting waste products from the blood. The major blood vessel that leads to the kidney is the renal artery. It comes from the liver, and the blood that travels in it contains urea. This substance is derived from proteins in our food. Digestion breaks down the protein substances in food, and that which is not utilized by the body is carried by the blood stream to the liver where it is changed into urea.
Now that the urea has reached the kidneys a remarkable extraction process takes place in a coiled tube called a nephron. Each of us has about a million nephrons which if stretched end to end in a line would be about 70 miles long.
As the blood enters the kidney it goes into small blood vessels called capillaries where it is filtered. A portion of the plasma (fluid part of the blood) enters the nephrons. The nephrons are able to separate out the good things (salts, sugars, amino acids, water) and return them to the blood. This process goes on continuously, and the nephrons are kept active returning the good substances back into the blood and rejecting the waste substances. This waste material is called urine. This passes out of the nephrons into collecting tubes called ureters and then to the bladder and is discharged from time to time.
This complicated but amazingly efficient system could never have happened by chance, nor could the most brilliant scientist begin to duplicate it. God alone could create and take care of this and every other part of our body as well. How wondrous His ways are! When we think of the wisdom that designed such an intricate body we should want to exclaim like the Psalmist did, "I will praise Thee; for I am fearfully and wonderfully made: marvelous are Thy works; and that my soul knoweth right well." Psa. 139:14.