The New Childrens Encyclopedia

YOUR BODY

273

TAKE A LOOK: CELLS

Every living thing begins life as a single cell. Your body is made up of millions of cells so small that, on their own, they can only be seen under a microscope. Cells group together to form tissues, which in turn make up our organs.

The cardiovascular or circulatory system

pumps blood around your body. Blood transports oxygen and other vital substances to your organs and tissues and then removes waste products.

The muscular system

is

made up of muscles attached to bones by tendons, smooth muscles in your organs, and heart muscle. Muscles need a regular blood supply to bring them the oxygen and energy they require to work efficiently.

The skeletal system

is the

moveable skeleton that provides a frame for your body and that protects your internal organs. An adult has 206 bones.

The digestive system

processes

the food you eat, taking out the nutrients your tissues need and getting rid of the waste. It is basically a long tube.

O

Epithelial cells form a protective

outer layer to the human body.O

Fat cells are blob shaped.

They get larger as the body stores more fat.O

Nerve cells transfer electrical

signals around the body to and from the brain.O

Smooth muscle cells are found in

the intestine. O

Photo receptor cells are found in

the eyes.

Skin covers your body. It contains hair follicles, nerve endings, sweat glands, and tiny blood vessels called capillaries.

There are about 10 body systems, but it’s difficult to state an exact figure, since the muscular system and skeletal system are sometimes combined and referred to as one system.

Each of the body’s systems has its own job to do. If all are functioning properly, they will work together to ensure the body’s overall health.

The heart is at the center of the circulatory system.

THE HUMAN BODY

Nucleus

Cell

Fats and sugars are

broken down

here.

Cell membrane



Skin cells