[MUSIC] Joan Cartan-Hansen, Host: A joint is where two bones connect.

You have fixed joints like those in the skull.

They don't move.

You have joints that move just a little, like the joints in the vertebrae in your spine.

And you have six kinds of moveable joints.

In a ball and socket joint, one bone has a rounded head and the other has a cup-like feature.

Your shoulder and hip have a ball and socket joint.

A hinge joint works like a door, opening and closing.

Your elbow has a hinge joint.

A pivot joint swivels like the joint that rotates your forearm.

A condyloid joint moves but doesn't rotate, like the finger joints.

A gliding joint has a smooth surfaces that slips over one another.

Your wrist has a gliding joint.

And finally, a saddle joint.

It allows movement back and forth and side to side, like the joint at the base of your thumb.

Without all of these different kinds of joints, you couldn't move.

And that's why they are an important part of the skeletal system.

For more information about skeletons and the skeletal system, check out the science trek website.

You'll find it at science trek dot org