In terms of muscle attachments, which structure is a lateral (distal) attachment site of the trapezius muscle?

• A. Spinous processes of T1–T12 vertebrae
• B. Lateral third of the clavicle
• C. Medial border of the scapula
• D. Mastoid process of the temporal bone

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the anatomy of the trapezius muscle, which has multiple attachment points including origins and insertions. The muscle originates from the spinous processes of the cervical and thoracic vertebrae and the external occipital protuberance.
2. Step 2: Identify the insertion points (distal attachments) of the trapezius muscle. These are the sites where the muscle attaches laterally and acts to move the shoulder girdle.
3. Step 3: Recall that the trapezius inserts on three main structures: the lateral third of the clavicle, the acromion process, and the spine of the scapula. These are all lateral (distal) attachment sites.
4. Step 4: Compare the options given: the spinous processes of T1–T12 vertebrae are proximal (origin) attachments, the medial border of the scapula is not an insertion site of the trapezius, and the mastoid process is part of the origin region.
5. Step 5: Conclude that the lateral third of the clavicle is the correct lateral (distal) attachment site of the trapezius muscle among the options provided.