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anatomy of the shoulder joint

shoulder anatomy

The shoulder is a ball-and-socket joint made up of three bones: the humerus, scapula, and clavicle. (Fig. 1)

The head of the humerus rests on the rounded part of the scapula. This place is called the glenoid fossa (Fig. 2). Surrounding the rim of the glenoid is a strong fibrous tissue called the glenoid labrum. The labrum deepens the glenoid and stabilizes the shoulder joint. It also serves as a connection point for the shoulder ligaments and one of the biceps tendons.

肩の骨 .jpg
​Figure 1: Bone structure of the shoulder joint
​ Figure 2: Shoulder glenoid
​Figure 3: Role of the shoulder labrum

A strong connective tissue called the joint capsule is the ligamentous system of the shoulder that holds the head of the humerus in the center of the glenoid. The shoulder capsule covers the shoulder joint and connects the head of the humerus to the scapula.

capsular lig shoulder .jpg
capsular lig role .jpg

The shoulder is also stabilized by strong tendons and muscles. Part of this muscle is called the rotator cuff. The rotator cuff consists of four muscles that come together like tendons that wrap around the head of the humerus, or form a cuff.

The biceps has two tendons that attach to the shoulder blade. The long head tendon attaches to the top of the glenoid. The short head tendon attaches to a place called the coracoid process. These work to keep the humeral head centered in the glenoid.

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