Bones and Muscles for Kids: How Your Skeleton Holds You Up (Grade 4 and Grade 5 Science)

Hi, I'm Luna from DoodleBeez. Today we are exploring your skeleton, the strong frame of bones inside your body. Without it, you would flop like a jellyfish! Let's find out how bones and muscles help you stand and move.

An adult skeleton has two hundred and six bones. Babies are born with more, but some join together as they grow. The longest bone is your thigh bone, called the femur. The tiniest bone is deep inside your ear.

Your bones have three big jobs. They support your body and give it shape. They protect soft parts, like your skull guarding your brain and your ribs guarding your heart and lungs. And they help you move.

Bones cannot move on their own. Muscles do the work. Muscles are joined to bones by strong cords called tendons. When a muscle contracts, it gets shorter and pulls on the bone. Muscles can only pull, never push.

That is why muscles work in pairs. Bend your arm, and the biceps on the front pulls it up. Straighten it, and the triceps on the back pulls it down. One muscle pulls while the other relaxes.

Places where bones meet are called joints. Your elbow and knee are hinge joints. They bend one way, like a door. Your shoulder and hip are ball and socket joints, so they can swing around in a circle.

Now it's your turn. Your knee bends forward and back, but not side to side. Is it a hinge joint or a ball and socket joint? Pause and try. It is a hinge joint, because it bends one way, like a door.

Great job! Two hundred and six bones support, protect and move you. Muscles pull on bones using tendons and work in pairs, and joints let you bend and turn. Practice bones and muscles in the Science Lab at doodlebeez.com. See you next time!