EXCRETION :

 

EXCRETION IN HUMAN BEINGS: Excretion is a process of removing the harmful metabolic waste from the body. Human body has number of organs which throws out the excretory wastes from the body like- Skin throws out sweat, Lungs throws out carbon dioxide, Kidneys throws out nitrogenous wastes like urea and uric acid and so on. But when we define excretory system we speak about number of organs involved there.

Excretory system in human beings consists of one pair of kidney, one pair of ureter, one urinary bladder and one urethra.

Kidney filters the waste products from the blood. Nitrogenous wastes like urea and uric acid are removed from the blood in the kidneys.

Kidneys are bean shaped structure, reddish brown and are placed in the lower abdominal cavity.

Functional unit of kidney is the Nephron just like the alveoli which is the functional unit of lungs. Each kidney has nearly one million Nephron. A nephron is a complex tubular structure, it is divided into following parts- Bowman’s capsule, Proximal convoluted tubule, loop of Henle’s , Distal convoluted tubule and finally collecting tubule.

The main function of the nephron is to filter the blood. In this process nephron returns to the body essential food materials but throws out the waste from the body.

Essential materials that are returned by the nephron and absorbed by the body are – Glucose, Vitamins, Minerals, Salts, Amino acids, etc. and the non  essential materials that are thrown out from the body are nitrogenous wastes like – urea , uric acid etc. along with water.

As we find in case of Lungs –alveoli which are surrounded by blood capillaries, same way kidney-nephrons  are also surrounded  by blood capillaries and help in the process of filtration.

A pair of ureter which is present in the excretory system connects kidneys with that of Urinary bladder. It is a tube like structure.

Urinary bladder is a muscular sac like structure, where urine gets accumulated  and moment it is filled up then by the process of micturition the urine is thrown out from the body (urinary bladder)through  Urethra.

EXCRETION IN PLANTS: In case of plants oxygen can also be considered as the excretory products.

Plants get rid of excess of water by the process of transpiration. 

In case of plants excretory products are stored as resins and gums. In most cases wastes are stored in leaves that fall off.

                                                         

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