Your body is comprised of joints, muscles, and structures that connect one bone to the next. A pectoral girdle, also referred to as the shoulder girdle, connects your upper limbs to the bones along the axis of your body. You have two pectoral girdles in your body.
The pectoral girdle consists of the two bones that make up your shoulder:
Your pectoral girdles are responsible for providing structural support to your shoulder region on the left and right side of your body. They also allow for a large range of motion, connecting muscles necessary for shoulder and arm movement.
The pectoral girdles on either side of your body aren’t joined together. This allows for your shoulder and arms to move and function independently.
The pectoral girdle is made up of two major bones: the clavicle and scapula.
The clavicle or collarbone is an S-shaped bone situated at the front of your body in a horizontal position. It supports your shoulder, encourages a full range of motion, and protects your nerves and blood vessels that pass between the trunk of your body and your upper limbs. Your clavicle provides the only direct connection between your pectoral girdle and axial skeleton.
Your clavicle has three parts:
- Medial end. This portion of the clavicle attaches to the sternum. The sternal end of the clavicle is triangular and forms the sternoclavicular joint.
- Lateral end. This portion of the clavicle attaches to the scapula. This flat piece is often referred to as the acromial end, and forms the acromioclavicular joint.
- Shaft. This is the body of the clavicle.
The clavicle is one of the most commonly fractured bones in the body.
There are also some physical differences in men and women. This bone is often shorter and less curved in women, while in men it’s longer and heavier with a more defined curve.
Unlike your clavicle, the scapula bone or shoulder blade is located at the back of your shoulder. It’s triangular and connects your humerus with your clavicle. The scapula provides an attachment point for a number of muscles in your shoulder and upper limbs to your neck and back.
Your scapula is divided into three borders:
- medial border (vertebral border), which runs parallel to the thoracic vertebrae
- lateral border (axillary border)
- superior border, the thinnest and shortest of the three borders
It also has two angles:
- lateral angle
- inferior angle
Injury or fracture to the scapula is uncommon, but can occur from severe chest trauma, sports injuries, or car collisions.
Pectoral girdle joints
There are four main joints in the pectoral girdle:
- Sternoclavicular joint. This joint is the point where your clavicle meets your sternum. This joint provides the direct attachment between your upper extremity and axial skeleton, and also allows your clavicle to move in three different planes.
- Scapulothoracic joint. Also known as the scapulocostal joint, this is where the scapula bone meets the ribs in the back of your chest. This joint relies on surrounding muscle for control.
- Acromioclavicular joint. This is the point where your clavicle meets the acromion of the scapula. Similar to the sternoclavicular joint, the acromioclavicular joint encourages motion in three planes.
- Glenohumeral joint. Also known as the shoulder joint, this is the ball-and-socket connection between the humerus and scapula.