What is the proximal attachment of the deltoid muscle?

The deltoid muscle has a proximal attachment that is crucial for its function in shoulder movement. This muscle originates from three distinct points: the lateral portion of the anterior border of the clavicle, the acromion, and the spine of the scapula. These three attachment sites allow the deltoid to cover a significant portion of the shoulder and contribute to its ability to abduct, flex, and extend the arm.

The attachment to the clavicle provides stability and a robust anchoring point for the anterior fibers, while the acromion and spine of the scapula serve as the lateral and posterior attachments, respectively, allowing the deltoid to act on the humerus in multiple planes of motion. This arrangement is essential for the deltoid's role in various shoulder movements, including raising the arm and rotating the shoulder.

Other choices do not accurately represent the proximal attachment of the deltoid, as they refer to different structures or locations relevant to other muscles or parts of the shoulder anatomy. The greater tubercle of the humerus, for instance, is where some of the rotator cuff muscles attach; the medial lip of the intertubercular groove is associated with the biceps brachii; and the supraspin