Long head of biceps brachii

Caput longum musculi bicipitis brachii · Dlouhá hlava dvojhlavého svalu pažního

Muscles

Looks like

The outer head of the biceps, whose long tendon starts above the shoulder socket and runs through the shoulder joint in a groove.

Bends the elbow, turns the palm up, and helps steady the shoulder.

Its tendon can fray or snap, leaving a 'Popeye' bulge; usually managed without surgery. Front-of-shoulder pain often comes from it.