Overview of Upper Limb - LO 3

3. Understand details (attachments, actions, innervation, blood supply, etc.) regarding the anterior and posterior compartments of the arm and forearm, as well as the deltoid m.

Click here for a downloadable PDF version of the individual muscle charts.

Click here for a downloadable PDF of a comprehensive muscle chart. 

*Students are only responsible for muscles discussed in the main text of the learning objectives and/or list of structures

Deltoid m. 

• Intrinsic shoulder muscle

• Joints crossed

  • Glenohumeral joint

• Innervation

  • Axillary n. (C5, C6)

• Blood supply

  • Axillary a. branches

• Actions

  • Dependent on part of muscle contracting 

  • All actions associated with glenohumeral joint, except adduction

    • Strong abductor of arm

Anterior compartment of arm

• Muscles (follow links for specifics of each muscle)

  • Coracobrachialis m.

  • Biceps brachii m.

  • Brachialis m.

• Joints crossed

  • Either glenohumeral, elbow, proximal radio-ulnar joints or all 3 joints

• Innervation

  • Musculocutaneous n. (C5-C7)

• Blood supply

  • Axillary or brachial aa.

• Actions

  • Flexion of either glenohumeral, elbow, or both joints

  • Adduction of glenohumeral joint

  • Supination of proximal & distal radio-ulnar joints

Posterior compartment of arm

• Muscles (follow links for specifics of each muscle)

  • Triceps brachii m.

  • Anconeus (seen in posterior forearm)

• Joints crossed

  • Glenohumeral (long head) and elbow joints

• Innervation

  • Radial n. (C6-C8)

• Blood supply

  • Deep brachial a.

• Actions

  • Extension at elbow joint

  • Long head has weak role in extension & adduction at glenohumeral joint

Anterior (flexor/pronator) compartment of forearm

This compartment is organized into three layers, largely with superficial muscles acting upon proximal joints, and intermediate and deep levels action upon progressively more distal joints.

These muscles are mostly innervated by the median n., with some contributions from the ulnar n.

Superficial Layer Muscles:

• Pronator teres

• Flexor carpi radialis m.

• Palmaris longus m.

• Flexor carpi ulnaris m.

Deep Layer Muscles:

• Flexor digitorum profundus m.

• Flexor pollicis longus m.

• Pronator quadratus m.

Posterior (extensor/supinator) compartment of forearm

The posterior compartment of the forearm is conceptualized in 2 layers: superficial and deep, largely with superficial muscles acting upon proximal joints, and deep levels action upon progressively more distal joints. These muscles are innervated by the radial n. and its branches.

Superficial Layer Muscles:

• Brachioradialis m.

• Extensor carpi radialis longus m.

• Extensor carpi radialis brevis m.

• Extensor digitorum m.

• Extensor digiti minimi m.

• Extensor carpi ulnaris m.