The muscles of the upper limb can be divided into 6 different regions: pectoral, shoulder, upper arm, anterior forearm, posterior forearm, and the hand.
There are 4 muscles of the pectoral region: pectoralis major, pectoralis minor, serratus anterior and subclavius. Collectively, these muscles are involved in movement and stabilisation of the scapula, as well as movements of the upper limb.
The muscles of the shoulder joint can be divided into an intrinsic and extrinsic group; The extrinsic group originate from the torso and attach to the bones of the shoulder, whereas the intrinsic ones originate from the bones of the shoulder and attach the humerus. They collectively act to move the upper arm and stabilise the shoulder joint.
The upper arm, located between the shoulder and elbow joint, has an anterior and posterior compartment. The muscles located in the anterior compartment are involved in flexion at the elbow and shoulder joint whereas muscle in the posterior compartment, triceps brachii, extends the arm at the elbow joint.
The muscles of the forearm are subdivided into an anterior and posterior compartment. The muscles of the anterior compartment are further divided into a superficial, intermediate and deep layer; Innervated by both the ulnar and median nerve, they collectively act to pronate the forearm and to flex the wrist and the digits.
The muscles of the posterior compartment are separated into a superficial and deep layer. These muscles are innervated by the radial nerve and are known as the extensor muscles due to their general action of extending the wrist and the digits.
The muscles of the hand can be divided into an extrinsic and intrinsic group. The extrinsic group originate from the forearm and attach to the bones of the hand, they are associated with forceful or non-precise movements. On the other hand, the intrinsic group originate and attach within the hand itself and are more involved with fine-tuned and delicate movements. Both groups are innervated by the ulnar and median nerve.
In this section, learn more about the anatomy of the muscles of the upper limb…
