The scapula is a roughly triangular bone, featuring three defining "vertices." These include the superior and inferior angles (which define the medial border of the scapula) and the neck of the scapula, which leads to the glenoid cavity.
The scapula (shoulder blade) is a roughly triangular bone which, with the clavicle, forms the pectoral, or shoulder, girdle. The humerus, or upper arm bone, articulates with the scapula to form the shoulder joint. This articulation takes place at the glenoid cavity, located at the upper, lateral angle of the scapula. The posterior of the scapula features a laterally running spine ,which separates the posterior surface into two unequal areas. This spine continues laterally and projects in the coracoid process and the acromion (which articulates with the medial end of the clavicle). Both of these projections serve as sites of attachment for connective tissue, and the spine and acromion anchor the trapezius and deltoids, specifically. These connections give the pectoral girdle a high degree of both flexibility and strength.
The body of the scapula features a broad, mostly flat surface on the
front and the back. This area is known as the subscapular fossa on
the anterior (front) surface. On the posterior surface, the area
is divided by the spine of the scapula. Above the scapular spine,
the surface is known as the supraspinous fossa, while the area below it
is called the subspinous, or infraspinous, fossa.
The clavicle, or collarbone, is a long, slightly curving bone which forms the frontal (anterior) part of each shoulder (pectoral) girdle. Located just above the first rib on each side of the ribcage, clavicles attach to the sternum in the middle of the chest, and laterally to the acromion of the scapula (forming the acromioclavicular joint).
The glenoid cavity forms the upper, lateral angle of the scapula, facing to the side of the body. This cavity serves as a site of articulation with the head of the humerus, or upper arm bone. Just to the posterior of the glenoid cavity is the acromion, which juts out from the spine of the scapula on its dorsal surface.
The shoulder joint, also known as the glenohumeral joint, is the articulation between the head of the humerus and the glenoid cavity of the scapula. The articulation is reinforced by connective tissue which creates the joint capsule. The coracohumeral ligament is one of these, reinforcing the capsule's upper part.
The humerus is a long bone which forms the upper arm. Its head (proximal end) is articulated with the scapula (at the glenoid cavity), while the distal end articulates with the bones of the forearm (radius and ulna) to form the elbow joint. The humerus features a large, bulbous prominence on the proximal end, which is just opposite the articular head. This prominence is called the greater tubercle, and serves, with the lesser tubercle and points on the scapula, as a site of attachment for the connective tissue which forms the shoulder joint capsule.
The coracoid process of the scapula is a short projection of bone from the neck of the scapula. This process serves as a site of attachment for the coracoacromial and coracoclavicular ligaments, the pectoralis major, the coracobrachialis, and the short head of biceps.
The acromion is the lateral projection from the spine of the scapula.
The ploughblade-like projection serves as a site of attachment for both
the trapezius and deltoid muscles, which assist in giving the shoulder
its strength during flexion.