Pectoral girdle


The pectoral girdle is commonly referred to as the shoulder. It is constructed by 2 clavicle bones and 2 scapulae. Though not considered a complete girdle because it only anterior attachment to the axial skeleton, joined at the sternum by the sternoclavicular joint, it is a delicate girdle considering that it bears no weight on a consistent basis.

Due to the lack of the posterior attachment, the pectoral girdle can achieve a high range of motion. The basic responsibility of the pectoral girdle is to perform basic structural support and areas for attachment for the various muscles in the region.

These muscles belong primarily to the elbow and shoulder joints.


Pectoral girdle
Image: Pectoral Girdle


The clavicle is commonly referred to as the collar bone and is slender in appearance. The S-shaped bone is the connecting point for the upper extremity to the axial skeletal structure. It also keeps the shoulder joint in place with ample room away from the trunk of the body to permit motion.


Image: Clavicle

The sternoclavicular joint is the joint responsible for the joining of the medial sternal extremity of the clavicle and the manubrium of the sternum. This leads to the lateral acromonial extremity and its juncture with acromion of the scapula.

This joint structure is known as the acromioclavicular joint. On the acromial extremity of the clavical resides a conoid tubercle. A costal tuberosity resides on the inferior surface of the sternal extremity. All of this is to provide the ligaments to the adjoining muscles a place to anchor.


The common term of shoulder blade is medically referred to as the scapula. This flat and triangular bone lies on the posterior of the rib cage over ribs 2 through 7. The bony ridge along the posterior surface of the scapula creates a prominent scapula spine. The spine serves the direct purpose of creating strength for the scapula and to assist it in resistance to bending and breaking.

The supraspinous fossa rests above the spine and the infraspinous fossa rests just below the spine. The spine begins to fan out and broaden toward the shoulder at the process known as the acromion. The clavicle attaches here, as do several surrounding muscles. A shallow depression known as the glenoid cavity lies just inferior to the acromion.

The head of the humerus slides perfectly into this shallow depression. Lying superior and anterior to the glenoid cavity lies the coracoid process, which is a thick upward projection. The subscapular fossa is a mildly concave surface that rests on the anterior surface of the scapula.


Image: Scapula

Three angles make up three borders of the scapula. The border closest to the vertebral column is known as the medial border. The superior border runs along the superior edge and the lateral border runs toward the arm. The superior angle rests between the medial and superior borders, and the inferior angle is between the medial and lateral borders.

The lateral angle naturally resides between the superior and lateral borders. The head of the humerus conjoins with the lateral angle of the scapula. The suprascapular nerve runs through the notch known as the scapular notch, which is a highly distinctive depression.

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