Pectoral Girdle
Pectoral girdle
- Connects the upper limb to the axial skeleton and provides muscle attachment sites for both the arm and back
- Comprises the clavicle (collarbone) and the scapula (shoulder blade)
Clavicle
Anatomy:
- Sternal end - flat medial end, articulates with manubrium of sternum
- Conoid tubercle - small bony projection where the conoid ligament attaches
- Acromion end – rounded lateral end, articulates with acromion of scapula
- Costal tuberosity (aka impression) - provides an attachment site for the costoclavicular ligament
- Superior surface - smooth
- Inferior surface - rough due to muscular attachments
- Cannot withstand heavy forces; fractures are common and can cause damage to the underlying brachial plexus and associated vessels.
- The clavicle is one of the first bones to begin ossification during fetal development, but is the last to complete ossification, during the mid-twenties.
- It is the only long bone that ossifies intramembraneously.
Scapula
Anatomy:
- Supraspinous fossa - superior to the spine
- Infraspinous fossa - inferior to the spine
- Body – triangular surface of scapula
- Superior angle – projects superomedially
- Inferior angle - projects inferiorly
- Lateral angle – projects laterally; includes the glenoid cavity
- Superior border - extends from the glenoid cavity to the superior angle
- Lateral (aka axillary) border - extends from the inferior angle to the lateral angle
- Medial (aka vertebral) border - extends from the superior angle to the inferior angle
- Subscapular fossa - anterior surface of the scapula; it is the attachment site for subscapularis
- Acromion - the most-superior extension of the scapula and arises from the scapula's posterior surface
- Coracoid process - extends from the superior aspect of the scapula and projects laterally
- Glenoid cavity (aka fossa) - laterally oriented cup-shaped depression where the humerus articulates with the pectoral girdle
- Glenoid labrum - rim of the glenoid cavity, composed of fibrocartilage and aids in humeral stabilization
- Supra- and infraglenoid tubercles - raised portions of bone above and below the glenoid cavity that provide muscle attachment sites for the biceps brachii and triceps brachii
- Scapular neck - the portion of the scapula that extends toward the glenoid cavity
- Spine of the scapula - prominent ridge of bone that separates the posterior scapula into superior and inferior portions
- Acromion process - projects laterally; it is a continuation of the spine of the scapula
- Suprascapular notch - a small indentation in the superior border medial to the coracoid process
- Superior transverse ligament - closes off this notch superiorly to create a foramen through which the suprascapular nerve traverses.
- Calcification of the superior transverse ligament can compress the suprascapular nerve and impair innervation to the posterior scapular muscles
- The scapula articulates with the acromial end of the clavicle and the head of the humerus (upper arm).
Additional Images:
Pectoral Girdle
Clavicle
Clavicle Muscles
Scapula