**Core Concept**
The axilla is a complex anatomical region where various structures converge. The posterior wall of the axilla is formed by the scapula, teres major muscle, and the long head of the triceps brachii muscle. Understanding the anatomical boundaries of the axilla is crucial for various clinical procedures and conditions.

**Why the Correct Answer is Right**
The correct answer is the structure that does not form the posterior wall of the axilla. The scapula forms the superior part of the posterior wall, while the teres major muscle forms the inferior part. The long head of the triceps brachii muscle also contributes to the posterior wall. The other options, such as the pectoralis major muscle, latissimus dorsi muscle, and subscapularis muscle, form other parts of the axillary wall or are involved in other anatomical structures.

**Why Each Wrong Option is Incorrect**
**Option A:** The pectoralis major muscle forms the anterior wall of the axilla, not the posterior wall.
**Option B:** The latissimus dorsi muscle forms the posterior wall of the axilla, but it is not the correct answer.
**Option C:** The subscapularis muscle forms the anterior wall of the axilla, not the posterior wall.

**Clinical Pearl / High-Yield Fact**
Remember the mnemonic "SCAT" to recall the structures forming the posterior wall of the axilla: Scapula, Teres major, and the long head of the Triceps brachii.

**Correct Answer:** D.