Muscles of upper limb (overview)

The muscles of the upper limb are organized to provide mobility, stability, and fine motor control. They can be divided into two main categories: muscles of the shoulder (scapulohumeral) muscles, which control the shoulder joint, and muscles of the free upper limb, responsible for movements of the arm, forearm, and hand. Each region is further organized into smaller compartments or muscle groups that work together to provide coordination and precise movements.

Shoulder (scapulohumeral) muscles

The shoulder (scapulohumeral) muscles connect the scapula and clavicle to the humerus and are primarily responsible for movements of the shoulder (glenohumeral) joint. They allow a wide range of motions, including flexion, extension, abduction, adduction, rotation, and circumduction. This group includes the deltoid, rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis), and teres major.

Muscles of the free upper limb

The muscles of the free upper limb are responsible for movements of the elbow, wrist, and hand. They are further subdivided into the following three groups:

• Arm muscles - located between the shoulder and elbow, these muscles are grouped into anterior and posterior compartments.
  • Anterior (flexor) compartment - includes biceps brachii, brachialis, and coracobrachialis; this group is primarily responsible for flexion at the elbow and shoulder.
  • Posterior (extensor) compartment - includes triceps brachii, which extends the elbow and assists in shoulder movements.
• Forearm muscles - situated between the elbow and wrist; these muscles are classified into anterior and posterior compartments, which are both separated by the interosseous membrane.
  • Anterior (flexor) compartment - divided further into superficial and deep parts; mainly involved in wrist and finger flexion and forearm pronation.
  • Posterior (extensor) compartment - subdivided into superficial and deep parts; primarily responsible for wrist and finger extension and forearm supination.
• Hand muscles - the intrinsic muscles of the hand that are organized into three groups based on their location and function:
  • Lateral or thenar group - controls thumb movements;
  • Middle or intermediate group - includes lumbricals, palmar interossei, and dorsal interossei, which facilitate fine motor movements like finger abduction, adduction, flexion, and extension at the metacarpophalangeal and interphalangeal joints;
  • Medial or hypothenar group - controls movements of the little finger.