The Excretory System

Function

The excretory system is the mechanism used by the body to remove any waste products of metabolism. The system helps maintain homeostasis for the healthy functioning the various organs. Organs such as the kidney, skin, lungs and large intestine contribute to remove our waste.

Kidneys

• The kidneys receive blood from the renal arteries and filter the wastes materials. The waste is then sent to the urinary bladder via the ureter. Regulating acid-base balance, electrolyte levels and blood pressure. The kidneys are also important for the process of reabsorption of water, amino acids and glucose.

Urinary bladderThe bladder is a hollow, elastic organ that stores urine. Urine enters the bladder from the kidney by the ureters and is expelled through the urethra. The average bladder holds 300-350ml of urine and expulsion is controlled by an automatic internal sphincter and a voluntary external sphincter.

Lungs

The lung’s job in the excretory system is getting rid of carbon dioxide and water. They achieve this by extracting carbon dioxide from the red blood cells in the alveoli. The carbon dioxide, along with water vapor from the alveolar surfaces is expelled from our bodies when we exhale.

SkinThe skin is used to cool our body temperature by excreting sweat. Sweat glands fall under two different categories; eccrine and apocrine. The eccrine glands are the smaller, main sweat glands found all over the body and secrete sweat through pores. The apocrine glands are larger, found mainly at the armpits and excrete more odorous sweat through tiny canals of the hair follicles.

Liver The liver is thought to be responsible for up

to 500 separate functions, usually in combination with other systems and organs. The process that the liver goes through is the elimination of waste and toxins that enter the body. The role that the liver has in the excretory system is removing different poisons in the blood and by doing this the liver must break down nutrients, changing into more basic elements called bile.

Random Facts

• Average humans urinate around 3000 times a year• An average person sheds 30000 to 40000 skin cells every

minute• You will excrete 138 kilograms of feces every year• You breathe about 14-20 times a minute (start counting)• The liver feels like rubber