Kidney Function

Kidney Function

Introduction and definition of terms:

The kidneys are the main organs in the urinary system. They filter

waste products out of blood from the renal artery. These are then

excreted. Useful solutes are reabsorbed into the blood. They also have

a major homeostatic role in the body, and help to control the water

content (osmoregulation) and pH of the blood.

Homeostasis is the maintenance of a constant internal environment

within a living organism.

Excretion is the removal from the body of waste products made in the

cells during metabolism.

Osmoregulation is the homeostatic control of body water. Water intake

needs to balance with water loss.

Urea is instantly converted from ammonia, as it is a less soluble and

less toxic compound. It is the main nitrogenous excretory product of

humans.

Each kidney receives its blood supply from the renal artery. The

kidney consists of millions of filtering units called nephrons. Blood

comes to the kidney under high pressure to make filtration efficient.

The filtered blood leaves the kidney along the renal veins.

The filtered waste products are excreted by the kidney as urine. A

narrow tube called the ureter carries urine from the kidney to the

bladder. From there the urine is excreted through a single tube,

called the urethra.

Kidney structure:

If you cut a section through the kidney, three areas can be seen:

§ The dark, outer region is called the cortex. It is here that

filtration is carried out by the nephrons. It is a dense capillary

network which receives blood from the renal artery.

§ The lighter, inner region is called the medulla. Each ...

... middle of paper ...

...pituitary to release antidiuretic hormone (ADH). The

release of ADH into the bloodstream brings about the following:

§ ADH make the distil convoluted tubule and the collecting duct more

permeable to water.

§ This allows more water to be reabsorbed from the distal convoluted

tubule and the collecting duct into the region of high solute

concentration in the medulla.

§ This produces a smaller volume of more concentrated urine.

If the blood has a high water potential (less concentrated), it is

detected and less ADH is secreted by the pituitary. This decrease in

the amount of ADH in the bloodstream result in the following:

§ The distil convoluted tubule and the collecting duct becomes less

permeable to water.

§ Less water is reabsorbed into the medulla.

§ Larger quantities of dilute urine are produced.