Final answer:
The muscle that lies in the subscapular fossa is the subscapularis. It is responsible for medially rotating the arm and is part of the rotator cuff.
Step-by-step explanation:
Which Muscle Lies in the Subscapular Fossa?
The muscle that lies in the subscapular fossa is the subscapularis muscle. The subscapularis is part of the rotator cuff, which is a group of muscles and tendons that stabilize the shoulder joint. It originates on the anterior surface of the scapula, in the subscapular fossa, and inserts into the lesser tubercle of the humerus. This muscle is responsible for the medial rotation of the arm.
Other muscles mentioned such as the teres major, infraspinatus, and supraspinatus, have different functions and locations in relation to the scapula. The teres major is located inferior to the teres minor, and it assists with extension, adduction, and medial rotation of the arm. The infraspinatus muscle lies inferior to the spine of the scapula and is involved in lateral rotation of the arm, while the supraspinatus, which sits superior to the spine of the scapula, helps with abduction of the arm.