SN7
SHORT NOTE
5M
Describe the breast with its lymphatic drainage. Add a note on the surface anatomy of the thorax.
The Breast
The breast (mammary gland) is a modified sweat gland lying in the superficial fascia of the anterior chest wall.
| Feature | Detail |
|---|---|
| Extent | 2nd to 6th ribs vertically; lateral sternal border to the mid-axillary line horizontally |
| Bed | Pectoralis major, serratus anterior and external oblique |
| Axillary tail (of Spence) | Pierces the deep fascia to enter the axilla — the only part deep to the deep fascia |
| Structure | 15–20 lobes, each with a lactiferous duct opening on the nipple; a lactiferous sinus near the opening |
| Ligaments of Cooper | Fibrous septa from the dermis to the deep fascia — suspend the breast |
Blood Supply and Lymphatic Drainage
- Arteries — internal thoracic (perforating branches), lateral thoracic, thoraco-acromial and the posterior intercostals
- Veins — follow the arteries; also communicate with the vertebral venous plexus, a route for skeletal metastasis
| Lymph drainage | Share | Destination |
|---|---|---|
| Axillary nodes | About 75% | Chiefly the anterior (pectoral) group, from the lateral quadrants |
| Internal mammary (parasternal) nodes | About 20% | From the medial quadrants; cross to the opposite side |
| Posterior intercostal nodes | Small | From the deep posterior part |
| Opposite breast and abdominal wall | Small | Via subdermal lymphatics; explains contralateral and abdominal spread |
Applied Anatomy of the Breast
- Peau d'orange — blockage of subdermal lymphatics causes oedema, while the ligaments of Cooper tether the skin, producing dimpling like orange peel
- Retraction of the nipple — from tumour infiltrating and shortening the ducts
- Fixity to the chest wall is tested by contracting pectoralis major with hands on hips
- The upper outer quadrant is the commonest site of carcinoma, because it contains the most glandular tissue
Surface Anatomy of the Thorax
| Landmark | Level or position |
|---|---|
| Suprasternal notch | T2–T3 vertebra |
| Sternal angle | T4/T5; 2nd costal cartilage |
| Xiphisternal joint | T9 |
| Apex beat | 5th left intercostal space, 9 cm from the midline |
| Nipple | 4th intercostal space in the male (variable in the female); dermatome T4 |
| Lower border of the lung | 6th rib mid-clavicular, 8th mid-axillary, 10th paravertebral |
| Lower border of the pleura | 8th, 10th, 12th at the same lines |
| Oblique fissure | From the spine of T3 to the 6th costochondral junction |
| Horizontal fissure | From the 4th costal cartilage to meet the oblique in the mid-axillary line |
Applied Aspects
- The apex beat is displaced in cardiac enlargement, and in mediastinal shift — toward a collapsed lung, away from an effusion or tension pneumothorax
All questions in Thorax
- Q1Define the mediastinum and describe its divisions with their contents. Add a note on the structures at the level of the sternal angle. ★
- Q2Describe the chambers of the heart, its conducting system and its blood supply. Add a note on the surface marking of the valves. ★
- Q3Describe the lungs with their lobes, fissures and root. Explain bronchopulmonary segments and add a note on the pleura. ★
- Q4Describe the diaphragm under origin, openings, nerve supply and actions. Add a note on its applied anatomy. ★
- Q5Describe the intercostal space with its muscles, vessels and nerves. Add a note on the thoracic cage and applied aspects. ★
- SN1Describe the coronary circulation with its branches and peculiarities. ★
- SN2Describe the pericardium with its layers and sinuses. Add a note on cardiac tamponade. ★
- SN3Describe the course and distribution of the phrenic nerve. Explain the referred pain to the shoulder. ★
- SN4Describe the azygos system of veins and its clinical importance. ★
- SN5Describe the course and drainage of the thoracic duct. Add a note on chylothorax. ★
- SN6Describe the formation, course and relations of the superior vena cava. Add a note on SVC obstruction. ★
- SN7Describe the breast with its lymphatic drainage. Add a note on the surface anatomy of the thorax.