Kidney(male)

=The Kidney=

The kidneys are specialised paired organs for excreting unwanted substances from the body. There is a left and right kidney on either side of the abdominal cavity. The right kidney sits beneath the liver and the left kidney sites beneath the spleen.

Kidneys include a series of arterioles or tubules called glomeruli. High blood pressure allows the diffusion of water out of the blood and into the glomeruli, with cell membranes restricting the movement of some salts and macromolecules and allowing the diffusion of others. Substances that are diffused out of the blood are then drained to the bladder where they are stored for later excretion from the body.

Early vertebrates had a primitive precursor to the kidney known as a pronephros (literally front kidney). More specialised vertebrates have a more advanced kidney known as the mesonephros. In the human fetus both pronephros and mesonephros form but they are not functional, with the placenta carrying out the role of filtering and excreting unwanted substances. The definitive kidney or metanephros forms last of all and is the functional kidney in adult humans. Parts of the mesonephros, particularly the duct, is incorporated into the male reproductive system.

Source:

Cartmill, Matt, William L. Hylander and James Shafland 1987. Human Structure. Harvard University Press, Cambridge, Massachusetts.