Anterior wall of axilla is formed by
**Core Concept**
The anterior wall of the axilla is formed by the pectoralis major muscle, which is a large, fan-shaped muscle that covers the anterior chest wall. Its anterior surface forms the anterior wall of the axilla, separating it from the anterior chest wall.
**Why the Correct Answer is Right**
The pectoralis major muscle is a powerful muscle that arises from the anterior chest wall and inserts into the humerus, enabling movements such as flexion, adduction, and medial rotation of the arm. The anterior surface of the pectoralis major muscle is in direct contact with the anterior wall of the axilla, making it the primary structure forming this wall.
**Why Each Wrong Option is Incorrect**
* **Option A:** The anterior wall of the axilla is not formed by the intertubercular groove of the humerus, which is a bony groove on the humerus that houses the tendon of the long head of the biceps brachii.
* **Option B:** The lateral wall of the axilla is formed by the intertubercular groove of the humerus, but not the anterior wall.
* **Option C:** The posterior wall of the axilla is formed by the subscapularis muscle and the teres major muscle, but not the anterior wall.
**Clinical Pearl / High-Yield Fact**
The axilla is an important region for lymphatic drainage of the upper limb, and the anterior wall of the axilla is a key landmark for identifying the axillary vessels and nerves.
**Correct Answer: C. Pectoralis major muscle.**