Upper Extremity Muscles

Directions

Print this PDF worksheet for a hardcopy guide as you work through this lesson.
Within the lesson click the red linked headings to bring up the desired starting point within the cadaver for your work.
Use the provided images on the worksheet to annotate and identify specific anatomical structures.

Brachium Muscles

As you have already seen, several back muscles are responsible for moving the humerus. The following muscles also contribute to motions of the arm and forearm:

biceps brachii - Locating this muscle in your specimen will be easy, however, you'll need to search a bit for the long and short heads of the muscle (and their tendons). This muscle spans both the shoulder and elbow joints. It flexes the the forearm at the elbow, supinates the forearm at the radioulnar joint, and flexes the arm at the shoulder.
coracobrachialis - Dissect away the biceps brachii (both heads and associated tendons) to gain an unobstructed view of the coracobrachialis. With its origin on the coracoid process of the scapula and insertion in the middle medial humerus shaft, this muscle flexes and adducts the arm at the shoulder joint.
brachioradialis - This muscle flexes the forearm at the elbow joint particularly when a quick movement is required or when a weight is lifted slowly during forearm flexion.
brachialis - Dissect away the brachioradialis to gain an unobstructed view of the brachialis. The "workhorse" of the elbow flexors is the brachialis. It is the most powerful flexor of the forearm at the elbow joint. This muscle wraps from anterior to posterior so rotate your specimen to view all of it.
triceps brachii - Rotate your specimen to a posterior perspective. The triceps brachii is the more powerful of the forearm extensors at the elbow joint. As its name implies, it has three heads of origin, one from the scapula (long head) and two from the humerus (lateral and medial heads). You will need to do some dissecting and rotating to locate the medial and lateral heads. Remember, you can always click the "Brachium Muscles" link to return to your starting perspective.

Posterior (Extensor) Compartment of the Forearm

Realize that your specimen isn't in anatomical position. The arms are folded inward across the pelvis. This means our anterior/posterior views of the forearm and hand are actually reversed. The "back" of the forearm is viewed from an anterior perspective. Rotate your specimen 45° to the anatomical right (Angle: 315°) to really get a good view of the posterior position of these muscles enabling them to perform their extensor function.

Nine muscles compose the posterior forearm extensor compartment (5 superficial and 4 deep). Collectively, these muscles extend the wrist, hand, thumb, and fingers. You are NOT responsible for identification of each individual muscle of this group. Learn them as one "posterior forearm extensor" group.

Anterior (Flexor) Compartment of the Forearm

Your specimen is now rotated to the posterior view so you are looking at the anatomical anterior (front) of the forearm. Remember, when your hands are in your lap the front of your forearm is oriented backward. Use the slider on the right below the dissection area to fade in the external anatomy to clarify and reinforce this orientation.

Six muscles compose the anterior forearm extensor compartment (6 superficial and 2 deep). Collectively, these muscles flex the wrist, hand, thumb, and fingers. Once again, you are NOT responsible for identification of each individual muscle of this group. Learn them as one "anterior forearm flexor" group. Rotate your specimen to the 45° orientation to gain the best perspective of these flexor muscles in the anterior (front) forearm position.

Intrinsic Hand Muscles

These muscles draw their name from the fact that they are located entirely within the hand. Located in the palm, they produce less powerful but more intricate and precise movements of the fingers and thumb.

As with the forearm flexors and extensors, learn these muscles as one group of "intrinsic hand muscles". You do NOT need to learn each individual muscle. :-)

Self-test Labeling Exercises