The shoulder is composed of several bones, muscles, ligaments, and tendons that work together to provide a wide range of motion and stability. The main bone of the shoulder is the scapula, commonly known as the shoulder blade, which connects to the clavicle (collarbone) and the humerus (upper arm bone). Here's a breakdown of the anatomy of the shoulder bone:
1. Scapula (Shoulder Blade):
- The scapula is a flat, triangular-shaped bone located on the upper back. It provides attachment points for several muscles and ligaments involved in shoulder movement and stability.
- Key features of the scapula include:
- Acromion Process: A bony projection at the top of the scapula that forms the highest point of the shoulder. It articulates with the clavicle to form the acromioclavicular joint.
- Glenoid Cavity (Glenoid Fossa): A shallow, concave depression on the lateral side of the scapula where the head of the humerus articulates to form the glenohumeral joint, commonly known as the shoulder joint.
- Coracoid Process: A hook-like structure located on the anterior surface of the scapula. It serves as an attachment site for various muscles and ligaments.
2. Clavicle (Collarbone):
- The clavicle is an S-shaped bone that runs horizontally between the sternum (breastbone) and the acromion process of the scapula.
- It provides support and stability to the shoulder, as well as serving as a strut to keep the shoulder joint away from the thorax, allowing for greater freedom of movement.
3. Humerus (Upper Arm Bone):
- While not part of the shoulder blade, the humerus is essential to the shoulder joint. It articulates with the glenoid cavity of the scapula to form the shoulder joint.
- The head of the humerus is large and rounded, fitting into the glenoid cavity of the scapula to form the ball-and-socket joint of the shoulder.
These bones are supported and connected by various muscles, tendons, and ligaments, which contribute to the stability and mobility of the shoulder joint. The shoulder is a highly complex structure that allows for a wide range of motion but also requires stability to prevent injury.