Muscles in the Human Body
Did you know you have more than 650 muscles in your body? These muscles help you move, but they also keep you alive – a lot of the time, you don’t even have to think about them! But what is a muscle, other than some fleshy stuff here and there around your body? Muscles are made up of a material that is sort of like an elastic band. It’s composed of tiny fibres that can shorten and lengthen when given a signal from your brain, a process called muscle contraction and relaxation.
There are a few different kinds of muscles in your body: skeletal, smooth and cardiac. You can read a little more about each kind below:
When you think of a muscle, you usually think about this kind, these muscles give your body strength and support. Skeletal muscles are controlled by you, so they can help you do things like carry your bag of Hallowe’en candy or rake leaves in your backyard. In order to move your limbs, skeletal muscles are attached to the ends of your bones by things called tendons. Tendons are made of very tough material so they can withstand all the moving your bones and muscles do every day!
Skeletal muscles come in lots of shapes and sizes – did you know the largest muscle in your body is called the gluteus maximus? You might know it as the fleshy pillow you sit on, aka your bum! You can find other large and strong muscles in your legs, like in your thighs. These muscles, also known as quadriceps, are important for keeping you upright and can get very strong with lots of running, biking, skiing and other athletic activities. But let’s not forget about your calves, the muscles on the lower part of your legs that give you that spring in your step – these are called soleus muscles.
There are of course many muscles in your upper body too! When you lift your big heavy pumpkin out of the pumpkin patch, a bunch of your arm, chest and back muscles are working together to help you carry it. The biceps at the front of your upper arm and triceps at the back of your upper arm help you hold onto the pumpkin, while the pectoralis major muscles in your chest and the deltoid muscles in your shoulders help you stand up straight and carry it all the way home.
Smooth muscles are mostly found inside your organs and they are what’s known as involuntary muscles. This means you can’t control them, no matter how hard you try. Smooth muscles are shaped like sheets and have lots of layers all attached together. In your digestive system, each organ has a few layers of smooth muscles which help your organs push all those candy apples you’ve eaten along so you can digest them.
You can also find smooth muscles in your eyes. Have you ever looked in the mirror in the dark, then turned on the light? If you have, you probably noticed your pupils (the dark black circles in the middle of your eyes) get smaller. This happens when smooth muscles in your eyes relax when there’s bright light and allow your pupils to close.
Cardiac muscles are a special set of muscles found in your heart that help you pump blood around your body. You also can’t control these – they work as an independent team to contract and relax so your heart beats on time. Cardiac muscles are also extremely thick and strong. They have to be able to pump blood from your heart to the tips of your toes in a fraction of a second!
Now that you’ve learned about the different kinds of muscles in your body, let’s go to the next post to learn how they work together with the skeletal system and the brain to let you move around.