Quite simply, muscles are tissues that move parts of the body by contracting or getting shorter.
The word muscle comes from the Ancient Romans who thought muscle movement looked like little mice running around the body. Their word for mouse was musculus.
We have around 650 skeletel muscles layered over our skeleton and they make up about half our body weight. They are attached to bones by tendons.
There are three types of muscles and most muscle is skeletel muscle.
For example, if we went to grab something with our arm, our brain would tell our arm muscle to work, thus shortening and pulling the bones to reach for the item, they are controllable.
Then there are the cardiac muscles, and these keep your heart beating. Finally, smooth muscle. These are found inside hollow organs such as the digestive tract, these muscles are automatic and cannot be controlled.
Muscles need oxygen to make energy. If the muscle is starved of oxygen maybe during a burst of activity, it produces a waste product known as Lactic acid. If this builds up in the muscle cells it can cause painful muscle cramps.
Your longest and strongest muscles are in your back as these help you to stand.
It is also said that it takes 12 muscles to smile but only 11 to frown and your tongue is made up of muscle.
Lastly, the tendons, these are what links the muscles to your bones, working together with muscles to pull bones into the correct position.
So you see we all need muscles, it just depends on us how well defined we want them to look.