Where is the proximal attachment of the subclavius muscle located?

The subclavius muscle is a small muscle that plays a role in stabilizing the clavicle during shoulder movements. Its proximal attachment, or origin, is specifically located at the junction of the first rib and its costal cartilage. This anatomical positioning allows the subclavius to effectively stabilize and protect the underlying structures, such as the brachial plexus and subclavian vessels, which are crucial for upper limb function.

Understanding the proximal attachment is essential because it helps in comprehending how the muscle contributes to movements and stability in the shoulder girdle. The other options given might refer to locations associated with different structures or muscles within the shoulder region, but they do not pertain to the subclavius, which distinctly originates at the first rib junction.