Sara Lawler, age 16, of Marion, Ohio, for her question:

HOW MANY BONES ARE IN THE WRIST?

The wrist is the joint that connects the hand and the forearm. This small area, which can move the hand up, down and sideways, is made up of eight small bones called "carpals."

Carpal bones extend across the hand in two rows of four bones each. Strong tissues called ligaments bind the carpals in place, but they also permit easy movement.

Three carpals of the upper row join the radius, one of the two bones of the forearm, to form the wrist joint. The ulna, the other bone of the forearm, does not connect with the carpals. It forms a joint with the radius just above the wrist. This joint permits the wrist to rotate and thus helps turn the palm of the hand up and down.

Cordlike tissues called tendons extend through the carpal area and connect the finger bones with muscles in the arm. When these arm muscles contract, they pull the tendons and make the fingers move. The tendons on the palm side of the carpals bend the fingers. Those on the back of the hand straighten the fingers.