The Muscular System

Lesson Plan - Get It!

Audio:

You use muscles all the time!

• Did you just use your finger to scroll down this page with your mouse?

That was controlled by muscles in your hands.

Before you move another muscle, if you missed or need a refresher on any The Human Body lessons, find them in the right-hand sidebar under Related Lessons.

Your body has a complex muscle system that functions to help you grow and move. There are more than 600 muscles in your body, each with a specific job! Some muscles are involuntary, meaning that they operate without instructions from the brain, while others are voluntary, and must be instructed to move.

• Can you think of a muscle that moves without any instruction from the brain?

The heart is a great example of an involuntary muscle!

The heart is made up of cardiac muscle, one of the types of muscles we have in our bodies. There are three types of muscles: smooth, cardiac, and skeletal muscles.

Smooth muscles have a smooth appearance because they are made of sheets or layers. Smooth muscle is involuntary, meaning that you cannot control it. Examples of smooth muscle include the esophagus, which passes food from the mouth to the stomach. It contracts to move food down without direction from the brain.

Watch Through the Esophagus The Function of Peristalsis and discover exactly how the esophagus works:

The muscles along your digestive tract contract and release to move the food through the intestines, where nutrients are taken in by the body. Smooth muscles are found throughout your body, helping you function daily.

Cardiac muscle is only found in the heart and is also involuntary. It is a very special type of muscle that helps the heart pump blood to the entire body. It is similar to skeletal muscle, but has a structure that allows the cells to contract in a wave-like pattern so the muscle acts as a pump for blood.

Watch a short video to see how the cardiac muscle in the heart pumps blood with Heart in 3D Animation: How the Heart Works from Elara Systems:

The last type of muscle is skeletal muscle, or striated muscle. This type of muscle is voluntary, and it helps us move. These are the muscles we use to run, jump, and kick a soccer ball.

Skeletal muscles work with your skeletal system to allow growth and movement. They are attached to bones by tendons. Tendons are dense, tough tissue that provide an attachment between bones and muscles.

All of these muscles work together to help you breathe, digest food, and enjoy time outdoors. Without involuntary muscles, you would have to control life processes like pumping blood and swallowing food. Voluntary muscles help us walk, lift toys, and swim. Both types are needed in order for you to grow and develop.

Discuss what you have learned about muscle types with a parent or teacher before moving on to the Got It? section, where you will explore more about muscle groups in the body.