Deep Fascia
The deep fascia divides the upper limb into anterior and posterior compartments. Muscles are organized into these compartments and have common attachments, innervations, and actions.
A. Cross-section of the arm and forearm showing the anterior compartments (flexors) and the posterior compartments (extensors). B. Upper limb divided into compartments.
Lies deep to the superficial fascia; the deep fascia primarily contains muscles, nerves, vessels, and lymphatics. The deep fascia of the upper limb is a continuation of the deep fascia covering the deltoid and pectoralis major muscles. It extends distally and gives off intermuscular septae, which extend to the bones, dividing the arm and forearm into anterior and posterior compartments. Each compartment contains muscles that perform similar movements and have a common innervation.
The muscles of the upper limb can be organized into the following groups.
- Scapular muscles. The muscles of the shoulder are primarily responsible for stability and movement of the scapulothoracic and glenohumeral joints. Muscular stability of the scapula is important because of the lack of bony stability. These muscles consist of the trapezius, deltoid, rhomboid major, rhomboid minor, serratus anterior, levator scapulae, pectoralis minor, and subclavius.
- Rotator cuff muscles. These muscles are considered a cuff because the inserting tendons blend with the glenohumeral joint capsule and provide stability and movement to the joint. These muscles consist of the supraspinatus, infraspinatus, teres minor, and subscapularis.
- Intertubercular groove muscles. The muscles of the intertubercular sulcus attach proximally to the scapula (pectoralis major and teres major) or the thorax (latissimus dorsi) and cross the anterior glenohumeral joint to attach to the humerus, medial to the intertubercular sulcus.
- Arm muscles. The deep fascia divides the arm into anterior and posterior compartments, with common actions and innervation.
- Muscles of the anterior compartment of the arm. Include the coracobrachialis, biceps brachii, and brachialis muscles. The muscles of the anterior compartment of the arm share common actions (flexion of the glenohumeral joint and/or elbow) and innervation (musculocutaneous nerve).
- Muscles of the posterior compartment of the arm. Consist of the triceps brachii muscle. The triceps brachii is a three-headed muscle that extends from the glenohumeral joint to the elbow and receives motor innervation via the radial nerve.
- Forearm muscles. The deep fascia divides the forearm into anterior and posterior compartments with common attachments, actions, and innervation.
- Muscles of the anterior compartment of the forearm. Many of these muscles share a common origin (medial epicondyle of the humerus), common actions (flexion of elbow, wrist, and digits), and common innervation (median and ulnar nerves).
- Muscles of the posterior compartment of the forearm. Many of these muscles share a common origin (lateral epicondyle of the humerus), common actions (extension of the elbow, wrist, and digits), and common innervation (radial nerve).
- Hand muscles. The intrinsic muscles of the hand consist of those that act on the thumb (thenar muscles), the little finger (hypothenar muscles), and lumbricals, dorsal interossei, and palmar interossei muscles.