Where is the Glenoid Cavity Located?

As per definition, a glenoid cavity is a section of the shoulder that is termed the glenoid cavity or glenoid scapula fossa. This is a pyriform articular surface, shallow, that is situated at the scapula's lateral angle. It is guided laterally, forward and articulates with the humerus head; it is wider below than above, the longest being its vertical diameter.

Along with the humerus, the whole cavity creates the glenohumeral joint. Each joint form is known as a joint of the synovial, ball and socket. By use of the broad head of the biceps tendon, the humerus is fixed in place inside the glenoid cavity. This tendon originally comes from the glenoid cavity's upper margin and coils over the shoulder, readying the humerus against the cavity.

In the fresh state, the cavity top is filled with cartilage, and its edges, slightly raised, glenoid labrum,  offer connection to a fibrocartilaginous structure that deepens the cavity. It is very susceptible to tearing of this cartilage. It is most often referred to as a SLAP lesion when torn, which is usually caused by repeated shoulder movements.

Site of Pectoral Girdle

The glenoid cavity is found in Pectoral Girdle. There are two scapulae in the pectoral girdle; each of the scapulae carries a spine, coracoid process, glenoid cavity and acromion system and thus glenoid cavity is present in Pectoral Girdle. The glenoid cavity is formed by the humeral head and gives the pectoral girdle flexibility. There are two coxal bones in the pelvic girdle, the sacrum and the coccyx. The cranium and the facial bones form the skull together. Sternum with ribs creates the rib cage.

Glenoid Cavity of Scapula

The scapula, also called the shoulder blade, is one of two large vertebrate shoulder girdle bones. These are found to be triangular in humans and reside between the levels of the second as well as eighth ribs on the upper back. The posterior surface of a scapula is disingenuously divided by a prominent ridge, the spine, which divides the bone into the infraspinatus and supraspinatus fossa, two concave regions. 

The spine and fossae provide an attachment to the muscles which rotate the arm. The spine ends in the acromion, a mechanism that articulates in front of the clavicle or collarbone helping to form the upper part of the socket of the shoulder.

Glenoid Cavity Anatomy - The triangle's lateral apex is widened and provides a deeper cavity, the glenoid cavity, that illustrates the shape of the shoulder joint mostly with the head of the upper arm bone, the humerus. A beaklike projection, the coracoid process, that finishes the shoulder socket, is overhanging the glenoid cavity.

Muscles that help to shift or repair the shoulder as required by movements of the upper limb are connected to the boundaries of the scapula.

Functions of Glenoid Cavity

• Dislocation is prevented in most cases by strong glenohumeral ligaments and muscles.  

• The glenoid cavity enables the shoulder joint to get the highest flexibility as compared to other joints. This flexibility is due to the shallowness of the glenoid cavity. By being so shallow, it allows 120 degrees of unsupported flexion.

• The extra range of movement in shoulder flexion (usually up to 180 degrees in humans) is often obtained by a mechanism known as scapulohumeral rhythm via the great mobility of the scapula (shoulder blade).

Evolution of the Glenoid Cavity

Definitions of the fossil remains that were given by Australopithecus africanus and A. afarensis indicates that in these animals, the glenoid fossa was much more cranial in orientation than in modern humans. This illustrates the significance of overhead limb postures and indicates that these hominoid primates maintain arboreal adaptations, while the lateral alignment of the glenoid of human populations illustrates the standard lowered arm position.

In dinosaurs- The major bones of the pectoral girdle in dinosaurs have been the coracoid and the scapula (shoulder blade), both of which were directly associated with the clavicle. The location on the scapula where the humerus (upper bone of the forelimb) articulates is called the glenoid. As it determines the range of movement of the humerus, the glenoid is essential.