Which of the following best describes the origin of the deltoid muscle?

• A. Lateral third of the clavicle, acromion, and spine of the scapula
• B. Inferior angle of the scapula
• C. Coracoid process of the scapula
• D. Intertubercular sulcus (bicipital groove) of the humerus

Answer: (A)

Verified step by step guidance

1. Understand that the origin of a muscle refers to the fixed attachment point, usually proximal, where the muscle begins on a bone or structure.
2. Recall the anatomy of the deltoid muscle, which is a large, triangular muscle covering the shoulder joint and responsible for arm abduction, flexion, and extension.
3. Identify the bony landmarks associated with the deltoid muscle's origin: the lateral third of the clavicle, the acromion, and the spine of the scapula are all parts of the shoulder girdle where the deltoid attaches proximally.
4. Compare the other options: the inferior angle of the scapula is a landmark for muscles like the latissimus dorsi, the coracoid process is the origin for muscles like the pectoralis minor and coracobrachialis, and the intertubercular sulcus of the humerus is an insertion site for muscles such as the latissimus dorsi and pectoralis major, not an origin for the deltoid.
5. Conclude that the best description of the deltoid muscle's origin is the lateral third of the clavicle, acromion, and spine of the scapula, as these are the correct proximal attachment points.