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Shoulder Joint Anatomy - Section 1 |
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The scapula, also known as the shoulder blade, is a large, flat bone located on each side of the upper back. The scapula has connections with the clavicle (or collar bone), the humerus (or upper arm bone), and is firmly attached to back by strong muscles. The scapula is a triangular shaped bone with four main structures, or prominences, that serve as key attachment points for bones, ligaments, and muscles. These prominences are located in such a way as to provide mechanical leverage for ligaments and muscles as they perform complex joint movements. Other flat areas on the scapula, called fossas, serve as attachment points for muscles of the rotator cuff. |
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The four bone prominences of the scapula include: the acromion, the coracoid, the spine of the scapula, and the glenoid fossa. |
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The front or anterior slide of the scapula is dish-like in nature, and serves as the origin for the subscapularis muscle - a broad flat muscle whose fibers go across the shoulder joint and attach on the upper arm bone, contributing the anterior or front portion of the rotator cuff (the sheath of musclo-tendinous tissue that surrounds the shoulder joint). |
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This anterior or front view of the shoulder joint shows the humerus separated from the scapula. Both the head of the humerus and the glenoid fossa are covered with smooth articular cartilage and allow the bone surfaces to articulate or move freely on one another. In the normal shoulder joint this results in pain-free, frictionless movement. |
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