The New Childrens Encyclopedia

MIGHTY MUSCLES

277

The sternocleidomastoid bends

your head forward. If just one

side contracts, it makes the head

turn or tilt.

O

Your largest and strongest muscles

are in your back, helping you to stand.

O

The word muscle comes from the

ancient Romans, who thought that

muscle movements looked like

mice running under the skin.

The ancient Roman word for

mouse was musculus.

O

Surprisingly, you use more

muscles to smile than you use

to frown! It takes 12 muscles to

smile and 11 to frown.

O

The first drawings of human

muscles were published in 1543

by Belgian scholar Andreas

Vesalius in his book On the

Structure of the Human Body.

O

Your tongue is made up of

muscles.

Tendons These are what

link muscles to bones,

working with muscles to pull

bones into position. They are

like cords and are incredibly

strong. Some tendons in your

hands stretch up to muscles

near the elbow, providing

huge flexibility and control.

TAKE A LOOK: MUSCLE FIBERS

Muscles are made up of

bundles of long cells,

organized into tissues called

muscle fibers. Each fiber is

incredibly thin—much

thinner than a human hair.

This is a magnified image of

skeletal muscle fibers.

 INSIDE EACH

MUSCLE FIBER are long

threads of protein. This image

has been magnified almost

400 times.

FAST FACTS

The chest muscle

(pectoralis major) pulls

your arms in toward your

body and is also used to

rotate the upper arms.

The forehead muscles

contract to make

frown lines.

THE HUMAN BODY