Pectoral Girdle

The pectoral girdle is the part of an appendicular skeleton. The main function of the pectoral girdle is to connect the upper limbs to the axial skeleton. The human skeleton is divided into two sections, they are the axial skeleton and the appendicular skeleton. The axial skeleton is made of 80 bones, including the skull, the vertebral column, ribs and the sternum. And the appendicular skeleton is made up of 12 bones including the pectoral girdle, the pelvic girdle and limbs. It is also known as the shoulder girdle because it consists of the shoulder part and also the attachment site for the humerus.

Pectoral Girdle Bones

It is mainly divided into two equal parts, and each part of the pectoral girdle consists of two bones namely the scapula (shoulder blade) and clavicle (collar bone). Pectoral girdle bones also help in the articulation of the axial limb to the axial skeleton: it also aids in the movement of arms and shoulders, the right and left parts of the shoulder which are not joined together and it allows independent movement. 

Anatomy of Pectoral Girdle

The pectoral girdle diagram shows that it is made up of two major bones -  

Scapula - 

It is also known as the shoulder blade, which is a triangular-shaped flat bone. It forms the posterior part of the shoulder girdle present dorsally in the thorax region between the second and the seventh ribs. 

• The spine of the scapula is an elevated ridge present on the posterior side of the scapula. The spine of the scapula also divides the convex posterior portion of the scapula into the smaller supraspinous fossa and the bigger infraspinous fossa. The ventral surface of the scapula faces ribs and there is a concave depression, called subscapular fossa.

• Acromion is a flat and expanded process, the spine extends laterally to form acromion. It articulates with the clavicle by the acromioclavicular joint to form an arch over the glenohumeral joint.

• The glenoid cavity is present below the acromion, It is in the form of depression at the lateral surface of the scapula. The head of the humerus articulates at the glenoid cavity by the glenohumeral joint.

• The coracoid process is a hook-like projection present above the glenoid cavity and below the clavicle and it is attached to the clavicle by a ligament. A coracoid process is a place where muscles of the arms and chest attach.

Clavicle - 

It is also known as the collarbone and it is a long s-shaped bone that forms the anterior part of the pectoral girdle and it is present horizontally. 

• The main function of the clavicle is to attach the upper limb to the sternum and it also transmits the force from the upper limb to the axial skeleton. The clavicle also protects the underlying nerves and vasculature and connects the upper limb to the trunk.

• The clavicle articulates with the sternum on one side and it articulates with the acromion on the other side.

• The important attachment site of the many muscles like deltoids. trapezius, sternohyoid, etc is the shaft portion.

• The clavicle is one of the most common fracture bone 

Pectoral Girdle Joints 

There are four main types of the pectoral girdle joint mentioned below - 

• Sternoclavicular Joint - 

It is a point where the clavicle meets the sternum and it provides the direct attachment between your upper extremity and axial skeleton. This joint also allows the clavicle to move in three different directions. 

• Scapulothoracic Joint - 

It is also known as a scapulocostal joint. This joint is found, where the scapula bone meets the ribs in the back of your chest and it relies on surrounding muscle for control. 

• Acromioclavicular Joint - 

This joint is a point, where the clavicle meets the acromion of the scapula. This also encourages motion in the three planes. 

• Glenohumeral Joint - 

It is also known as the shoulder joint, which is the ball socket connection between the humerus and scapula.  

Pectoral Girdle Function 

• The pectoral girdle connects the arm to the rest of the skeleton and It also provides support and stabilization, which allows the shoulder to move.

• Scapula primarily provides structural support to the shoulder and it can move in six different directions. These directions are protraction, retraction, elevation, depression, upward rotation and downward rotation.

• The main function of the clavicle is to attach the upper limb to the sternum and it also transmits the force from the upper limb to the axial skeleton. The clavicle also protects the underlying nerves and vasculature and connects the upper limb to the trunk.

• The omohyoid muscle that controls the hyoid bone of the neck also attaches to the scapula and in total there are a total of 17 different muscles that attach to the scapula.

Conclusion 

After going through the complete information provided above which included pectoral girdle definition, pectoral girdle bones, functions, and also anatomy, we can understand that the pectoral girdle is very important to provide structural support to the shoulder region on the left and right side of the human body. They are also important to provide a large amount of motion to the connecting muscles for the movement of the shoulder and arm.