Which muscle primarily stabilizes the humeral head in the glenoid cavity?

The subscapularis muscle plays a critical role in stabilizing the humeral head within the glenoid cavity. This muscle is one of the four rotator cuff muscles, and its primary function is to provide support and stability to the shoulder joint. The subscapularis is located on the anterior side of the scapula and it attaches to the lesser tubercle of the humerus.

When the subscapularis contracts, it helps to hold the humeral head securely against the glenoid cavity during movements of the arm, preventing dislocation and ensuring proper mechanics of the shoulder joint. Its action is particularly important during activities that involve lifting or rotating the arm, as these movements can create potential instability in the shoulder.

In contrast, the pectoralis minor, deltoid, and pectoralis major have different functions. While the pectoralis major and minor are involved in shoulder movements, they do not play a direct stabilizing role for the humeral head. The deltoid is primarily responsible for lifting the arm and providing mobility rather than stabilization of the joint. Therefore, the subscapularis is essential for maintaining the integrity and stability of the shoulder joint during various activities.