Lessons 17 & 18

How does the body get rid of wastes?

Can you imagine a city without sewers?

Or no garbage removal?

Waste materials pile up and before long………

How could we survive?

Your body must get rid of wastes, too. You can not live without getting rid of waste products.

Your body makes several kinds of waste materials.

There are two main groupings of waste in your body:Undigested solid wastes

Wastes made by the cells

You have learned that undigested solid wastes leave the body through the large intestine.

This is called elimination.

The cells make different wastes. These wastes include:water heat carbon

dioxidesalts urea

Urea is a nitrogen based compound.

The removal of waste products from the body is called excretion.

In excretion, blood picks up the wastes from the cells. The wastes are sent to special organs that pass them out of the body.

In many animals, carbon dioxide, heat, and water leaves the body through the lungs.

The liquid waste urine is made in the kidneys. Urine is water, urea, salts and heat.

Heat and water, as well as salt, are excreted by the body through the skin as perspiration.

The skin excretes most of the body’s waste heat. In addition, the skin removes some water, salts, and a very small amount of urea.

Perspiration, or sweating, also helps your body keep cool.

When sweat evaporates from your skin, it cools the body. As sweat evaporates, it removes heat from your body.