Subdivisions of the Parietal Pleura
The parietal pleura is divided into four parts according to the surface it lines:
- Costal pleura
- Diaphragmatic pleura
- Mediastinal pleura
- Cervical pleura (dome of pleura)
1. Costal Pleura
- Lines the inner surface of the thoracic wall — ribs, costal cartilages, intercostal spaces, and the sides of the vertebral bodies
- Attached to the thoracic wall by a thin layer of loose areolar tissue — endothoracic fascia
- In the living, the endothoracic fascia is easily separable from the chest wall (allows surgical access)
- Becomes continuous with diaphragmatic pleura inferiorly and mediastinal pleura medially
2. Diaphragmatic Pleura
- Covers the superior surface of the diaphragm
- Continuous medially with the mediastinal pleura
- Continuous laterally with the costal pleura
- In quiet respiration, the costal and diaphragmatic pleurae are in apposition (opposition) below the inferior border of the lung — forming the costodiaphragmatic recess
3. Mediastinal Pleura
- Lines the lateral surface of the mediastinum — forms its lateral boundary
- Reflected at the root of the lung as a cuff around the structures entering and leaving the lung, then becomes continuous with the visceral pleura
- Below the root, the reflection hangs down as the pulmonary ligament
- Contributes to the lateral walls of the pericardial sac anteriorly
4. Cervical Pleura (Dome of Pleura)
- The dome of the parietal pleura — projects upwards through the superior thoracic aperture into the root of the neck
- Extends: ~2.5 cm above the medial one-third of the clavicle and ~5 cm above the first costal cartilage
- Covers the apex of the lung
Relations of the Cervical Pleura
| Relation | Structure |
|---|---|
| Anterior | Subclavian artery (arches across at the highest point); subclavian vein (antero-inferior to the artery); internal thoracic artery |
| Posterior | Neck of the 1st rib; structures on it |
| Lateral | Scalenus medius muscle |
| Medial | Large vessels of the neck (brachiocephalic vessels) |
Suprapleural Membrane (Sibson’s Fascia)
A thickened layer of endothoracic fascia that forms a tent over the cervical pleura, protecting it:
- Attached from the transverse process of C7 to the inner margin of the 1st rib
- Separates the subclavian vessels from the pleura
- May contain rudimentary muscle fibres — scalenus minimus — which tighten the membrane and help maintain the dome despite changes in intrapleural pressure
Clinical importance: The cervical pleura is vulnerable to damage during:
- Subclavian artery/vein cannulation
- Brachial plexus blocks (especially interscalene approach)
- Neck dissections and supraclavicular lymph node biopsies Inadvertent puncture → pneumothorax
Summary: The Four Parts
| Part | What it Lines | Special Feature |
|---|---|---|
| Costal | Inner thoracic wall | Attached via endothoracic fascia |
| Diaphragmatic | Superior surface of diaphragm | Forms costodiaphragmatic recess with costal pleura |
| Mediastinal | Lateral mediastinum | Reflects at root → pulmonary ligament |
| Cervical | Dome into root of neck | Protected by suprapleural membrane; 2.5 cm above clavicle |