Muscles In The Human Body - How do muscles work?

The human body has 639 muscles.

Not all are joined to your bones.
For example, muscles line your blood vessels to keep blood flowing.
Your lungs work because of regular muscle movement.
Some muscles move only when you decide to stand up, sit down, or move in other ways.

These are the voluntary muscles that are joined to your bones. 

There are other muscles that work without your thinking about them.

These involuntary muscles are made of smooth muscle fibers. They mash the food material in your stomach and then act to move it along through your intestines.

Your heart is made of another special kind of muscle called cardiac muscle. It moves in a regular rhythm as it pumps blood to all parts of your body.

Muscles In The Human Body

How do muscles work?

Muscles are made of tough, elastic tissue. They are built so that they can contract, which means that they become shorter.
When the muscles whose ends are joined to bones contract, they pull at the bones and make them move.
Muscles are made up of long, thin cells that join together to make muscle fibers.
When the muscle becomes shorter, all the fibers move closer together, making the muscle bulge. You can see your muscles bulging and relaxing when you move your arms and legs.
If you bend your elbow and clench your fist, the muscles called biceps in your upper arm will bulge.

Muscles can only pull—they can’t push. 

Muscles whose ends are joined to bones work in pairs. One muscle contracts and pulls the bone one way, and the other contracts to pull the bone back again.

Interesting Facts About Muscles

• Human muscle cells produce enough heat every day to boil almost 2 pints of water for an hour.
• The tongue is the strongest muscle in the human body. 
• Muscles make around 40% of human body weight.
• We utilize more than 200 muscles just to make one step.
• The foot is responsible for one quarter of all the human body’s muscles
• Fingers do not have muscles in them, since they are moved by tendons and attached to muscles in the forearm. 
• When we shiver, our muscles contract involuntarily and this releases energy that keeps the body warm.
• The heart beats more than 4500 times each hour since the cardiac muscle never gets tired.  While sleeping, playing sport, resting even when going into the toilet, the hearth beats on average 80 beats per minute. 
• While smiling, we are using about 30 muscles, which control the eyelids, nostrils and brow, working together to show emotions.