This muscle (D) flattens the cheek (as in whistling or blowing a trumpet).

This muscle (F) pulls the corners of the mouth inferiorly, producing a downward sag of the mouth (the "sad clown" face).

This muscle (H) lies over the temporal bone and helps the masseter close the jaw.

This muscle (I) covers the posterior aspect of the skull and pulls the scalp posteriorly.

This chewing muscle (J) closes the jaw by elevating the mandible.

This muscle (K) flexes your neck. Some people call this the "prayer" muscle. It can also rotate the head toward the shoulder and tilt the head to the side.

This triangle-shaped muscle (A) forms the rounded shape of your shoulders, abducts the arm, and is a favorite injection site.

This large fan-shaped muscle (B) covers the upper part of the chest. It adducts and flexes the arm.

This two-headed muscle (C) bulges when the elbow is flexed.

This muscle (D) flexes the elbow and lifts the ulna.

This fairly weak muscle (E) resides mainly in the forearm.

These paired straplike muscles (A) are the most superficial muscles of the abdomen. They flex the vertebral column and compress the abdomen during defecation, childbirth, and forced breathing.

The deepest muscles (B) of the abdomen run horizontally across the abdomen.

These muscles (C) flex the vertebral column, rotate the trunk and bend it laterally.

These muscles (D) flex the vertebral column, rotate the trunk and bend it laterally.

These diamond-shaped muscles (A) extend the head, elevate, depress, adduct, and stabilize the scapula.

These muscles (C) on the posterior humerus extend the elbow. Called the "boxer's" muscle because it can deliver a straight-arm knockout punch.

The two large, flat muscles (D) that cover the lower back, extend and adduct the humerus.