M01.05.011 Mammary Glands

The breasts are paired structures located on the anterior thoracic wall, within the pectoral region. While present in both males and females, they are more prominent in females following puberty due to the presence of functional mammary glands essential for lactation.

Surface Anatomy

Location

• Horizontal Extent: From the lateral border of the sternum to the mid-axillary line.
• Vertical Extent: Between the 2nd and 6th costal cartilages.
• Underlying Muscles: Lies superficially to the pectoralis major and serratus anterior muscles.

Regions of the Breast

1. Circular Body: The largest, most prominent portion.
2. Axillary Tail: Extends along the inferior lateral edge of the pectoralis major towards the axillary fossa.

Key Features

• Nipple: Central structure composed of smooth muscle.
• Areola: Pigmented skin surrounding the nipple, containing sebaceous glands that secrete a protective oily substance during pregnancy.

Anatomical Structure

Mammary Glands

• Modified sweat glands consisting of 15–20 lobules.
• Each lobule contains alveoli that drain via a lactiferous duct converging at the nipple.

Connective Tissue Stroma

1. Fibrous Component:
   • Forms suspensory ligaments (Cooper’s ligaments).
   • Functions:
     • Attaches the breast to the dermis and pectoral fascia.
     • Separates secretory lobules.
2. Fatty Component: Provides padding and structural support.

Pectoral Fascia

• A flat connective tissue sheet underlying the breast, serving as the attachment for suspensory ligaments.
• Retromammary Space: Loose connective tissue layer between the breast and fascia, utilized in reconstructive surgery.

Vasculature

Arterial Supply

• Medial Aspect: Internal thoracic artery (branch of the subclavian artery).
• Lateral Aspect:
  • Lateral thoracic and thoracoacromial branches (from the axillary artery).
  • Lateral mammary branches (from posterior intercostal arteries).
  • Mammary branches (from anterior intercostal arteries).

Venous Drainage

• Follows the arteries, primarily draining into axillary and internal thoracic veins.

Lymphatic Drainage

• Crucial for understanding breast cancer metastasis.

Nerve Supply

• Innervation: Anterior and lateral cutaneous branches of the 4th–6th intercostal nerves.
• Function: Sensory and autonomic control (smooth muscle and vessel tone).
• Note: Milk production and secretion are regulated hormonally (prolactin and oxytocin) rather than by neural mechanisms.

Clinical Relevance

Breast Cancer

1. Epidemiology:
   • Most common cancer in women.
   • Second-highest cancer-related mortality after lung cancer.
2. Common Signs:
   • Nipple Changes: Deviation or retraction.
   • Peau d’Orange: Skin dimpling due to lymphatic obstruction.
   • Larger Dimples: Result from fibrosis and suspensory ligament traction.
3. Metastasis:
   • Begins in axillary lymph nodes (stony hard and fixed).
   • Can spread to liver, lungs, bones, and ovaries.
4. Diagnosis:
   • Triple Assessment: Clinical exam, imaging (mammogram/ultrasound), and biopsy.
   • Staging: I-IV or TNM system.
5. Treatment:
   • Surgery: Local resection or mastectomy.
   • Adjuvant Therapy: Radiotherapy and chemotherapy.

Points to Remember

• The suspensory ligaments provide structural integrity and can be affected in pathological conditions.
• The retromammary space is a key area in breast surgeries.
• Axillary lymph nodes play a critical role in lymphatic drainage and cancer metastasis.
• The triple assessment is standard for suspected breast cancer.

Bibliography

1. Anatomy texts and atlases (e.g., Gray’s Anatomy).
2. Relevant clinical guidelines on breast cancer (e.g., American Cancer Society).