SN2
SHORT NOTE
5M
★ High-yield
Describe the pericardium with its layers and sinuses. Add a note on cardiac tamponade.
Definition
The pericardium is a fibroserous sac enclosing the heart and the roots of the great vessels, lying in the middle mediastinum.
Layers
| Layer | Description |
|---|---|
| Fibrous pericardium | Tough, inelastic outer sac. Fused below with the central tendon of the diaphragm; above with the adventitia of the great vessels; attached to the sternum by the sternopericardial ligaments |
| Serous — parietal layer | Lines the inner surface of the fibrous pericardium |
| Serous — visceral layer (epicardium) | Adherent to the surface of the heart |
| Pericardial cavity | Potential space between the two serous layers, with 15–50 mL of fluid |
Pericardial Sinuses
| Sinus | Position | Surgical use |
|---|---|---|
| Transverse sinus | Between the arterial (aorta and pulmonary trunk) in front and the venous (SVC and atria) behind | A ligature can be passed round the great arteries here during cardiac bypass |
| Oblique sinus | Behind the left atrium, bounded by the pulmonary veins and the inferior vena cava; a cul-de-sac | Allows the left atrium to expand; approached in some posterior procedures |
Nerve and Blood Supply
- Fibrous and parietal serous pericardium — phrenic nerve (C3, 4, 5); sensitive to pain, referred to the shoulder tip
- Visceral pericardium — autonomic; insensitive
- Arteries — pericardiacophrenic, musculophrenic, bronchial, oesophageal and superior phrenic
Functions
- Restricts sudden overdistension of the heart, because the fibrous layer is inelastic
- Reduces friction during the cardiac cycle
- Anchors the heart in the mediastinum
- Acts as a barrier to the spread of infection from the lungs and pleura
Applied Aspects
- Beck triad — hypotension, raised jugular venous pressure, muffled heart sounds
- Pulsus paradoxus — an exaggerated fall in systolic pressure on inspiration, more than 10 mmHg
- As little as 150–200 mL accumulating rapidly can be fatal, whereas a slow effusion may reach 1–2 litres, because the sac stretches over time
- Pericardiocentesis — needle inserted in the left xiphocostal angle at 45°, directed toward the left shoulder, avoiding the pleura and the internal thoracic artery
- Constrictive pericarditis — often tuberculous in India; the thickened calcified sac restricts filling, giving a raised JVP with Kussmaul sign and a pericardial knock
- Pericarditis gives sharp retrosternal pain relieved by sitting forward, with a friction rub and saddle-shaped ST elevation
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.