🩷 Breast Anatomy & Physiology
Structure, boundaries, vasculature, lymphatics, nerve supply, Cooper’s ligaments, hormonal physiology — MRCS high-yield.
Overview & Boundaries
What Is the Breast?
The breast is a modified apocrine sweat gland that lies within the subcutaneous fat of the anterior chest wall, situated between the superficial and deep layers of the superficial fascia. It has no true capsule — the gland merges imperceptibly with the surrounding subcutaneous fat, which has important implications for surgical resection margins in breast cancer.
The breast overlies the pectoralis major (and partly serratus anterior and external oblique) and rests on the deep pectoral fascia. A layer of loose areolar tissue — the retromammary space (of Chassaignac) — separates the posterior breast from the deep fascia, allowing the breast to move freely on the chest wall.
| Feature | Detail |
|---|---|
| Vertical extent | Ribs 2–6 (some texts quote clavicle as upper boundary — both acceptable) |
| Deep surface | Rests on pectoralis major fascia (and serratus anterior + external oblique laterally) |
| Retromammary space | Loose areolar plane between posterior breast and deep pectoral fascia — allows breast mobility; plane used in subpectoral implant placement |
| Axillary tail (Tail of Spence) | Lateral prolongation of the upper outer quadrant — extends through the clavipectoral fascia into the axilla; can be palpated; may harbour breast tissue (and cancer) within the axilla |
| No capsule | Critical for surgery — no anatomical plane demarcates gland from surrounding fat; margins must be assessed histologically |
Breast Anatomy Diagram
