Muscles are made of a special kind of body tissue that is very flexible. They are located between your bones and your skin. Some muscles are inside of your organs, like your heart and stomach. Muscles are able to contract, or pull, to help your body move. Muscles grow with you as you grow. Once you are fully grown, they can also grow stronger from exercise, such as lifting weights. Check out this website to see magnified pictures of muscle tissue.
Muscles turn energy into motion - they are like the engines or motors of your body. They are what allow you to move. Even though you have an amazing skeleton system (your bones), without muscles, you wouldn't be able to move your bones an inch! There are a total of about 630 muscles in your body and each one serves a special purpose. Lots of muscles work together to help you move or even just stay balanced. When you are standing still, your body needs 300 different muscles just to keep you from falling over! That's nearly half of the muscles in your whole body. Eating, running, jumping, kicking, catching, playing talking, and lots of other activities that we do every day require muscles.
There are three types of muscle in the human body: skeletal, cardiac, and smooth. All of the muscles in your body together are called the muscular system.
Skeletal muscles attach to bones, and are voluntary--you can control them with your brain, which sends signals through nerves telling the muscles to move. Most of the muscles in your body are skeletal muscles - they are the ones that allow you move your arms and legs, make funny faces, and wiggle your toes. Many skeletal muscles are connected to your bones through tendons. Being connected to bones is what makes it easy for your body to move when your muscles are working. Skeletal muscles usually come in pairs. When one muscles works, or contracts, it moves a part of your body in one direction. To move it back, the opposite muscle has to contract! For example, if you stretch your arm out in front of you and bend it at the elbow, your bicep muscle contracts. To straighten your arm back out, your triceps muscle contracts and the bicep relaxes back to normal!
Did you know that your heart is made mostly of muscle? The type of muscle in your heart is called cardiac (say: kar-dee-ak) muscle, and the heart is the only place in your body where it is found. This muscle is very durable and strong, but it is also a little bit flexible. This allows the heart to pump blood all through your body. The cardiac muscles move in and out, pumping blood through your veins, and allowing blood to move back into your heart, so it can keep circulating. Your heart beats about 100,000 times every day! In one day, the blood in your body travels a total of 12,000 miles - that's like traveling across the US from coast to coast four times! The muscles in your heart move in and out, so that your heart pumps without you even having to think about it. Muscles that move this way are called involuntary.
Smooth muscles cause movement inside your body in places you don't often notice. They help you digest food by pushing it down your esophagus and into your stomach and then on into your intestines. Your eyes also have smooth muscles that help you focus on things. Even your blood vessels have smooth muscles to help move blood through your body. These muscles can stretch a lot. They can also maintain the stretch for a long time without tearing. They are usually in layers. Smooth muscles are involuntary, too--they work automatically, whether you ever think about them or not!
Teach kids about major muscles like biceps and quadriceps, where they are located, and actions they are used for with the labeled diagram on this worksheet. The bottom part provides space to draw pictures of activities that use the muscles shown. It also works well in conjunction with the Muscles in Motion science project.