Upper Limb - Human Anatomy - Musculoskeletal System - Shoulder Girdle

Shoulder Girdle

The shoulder girdle or pectoral girdle, composed of the clavicle and the scapula, connects the upper limb to the axial skeleton through the sternoclavicular joint (the only joint in the upper limb that directly articulates with the trunk), a ball and socket joint supported by the subclavius muscle which acts as a dynamic ligament. While this muscle prevents dislocation in the joint, strong forces tend to break the clavicle instead. The acromioclavicular joint, the joint between the acromion process on the scapula and the clavicle, is similarly strengthened by strong ligaments, especially the coracoclavicular ligament which prevents excessive lateral and medial movements. Between them these two joints allow a wide range of movements for the shoulder girdle, much because of the lack of a bone-to-bone contact between the scapula and the thoracic cage. The pelvic girdle is, in contrast, firmly fixed to the axial skeleton, which increases stability and load-bearing capabilities.

The mobility of the shoulder girdle is supported by a large number of muscles. The most important of these are muscular sheets rather than fusiform or strap-shaped muscles and they thus never act in isolation but with some fibres acting in coordination with fibres in other muscles.

Muscles

of shoulder girdle excluding the glenohumeral joint

Migrated from head

Trapezius, sternocleidomastoideus, omohyoideus

Posterior

Rhomboideus major, rhomboideus minor, levator scapulae

Anterior

Subclavius, pectoralis minor, serratus anterior