Surface Markings of the Pleura
The lines of pleural reflection can be marked on the chest wall as four lines. Knowledge of these lines is essential for clinical and surgical procedures.
1. Cervical Pleura (Dome)
Represented by a curved line with convexity directed upwards, drawn:
- From the sternoclavicular joint to the junction of the medial and middle thirds of the clavicle
- The summit (apex) of the dome lies 2.5 cm above the medial one-third of the clavicle
(Same on both sides.)
2. Anterior Line of Pleural Reflection (Costomediastinal Line)
Marks where the costal pleura reflects onto the mediastinum anteriorly. Differs on the two sides.
Right Side
- From the right sternoclavicular joint → downwards and medially to the midpoint of the sternal angle
- Then vertically downwards to the midpoint of the xiphisternal joint
- Then crosses to the right xiphicostal angle
Left Side
- From the left sternoclavicular joint → downwards and medially to the midpoint of the sternal angle (same as right up to this point)
- Then vertically downwards to the level of the 4th costal cartilage
- Then arches outwards to the sternal margin and descends a short distance lateral to the sternal margin
- Reaches the 6th costal cartilage, ~3 cm from the midline
Why the left differs: The heart and pericardium project to the left below the 4th costal cartilage, pushing the left lung away — creating the cardiac notch of the left lung and the area of superficial cardiac dullness.
Between the 2nd and 4th costal cartilages: The right and left anterior pleural lines lie in close apposition (or touch) in the midline — this is where the thymus (or its remnant) lies in the anterior mediastinum.
3. Inferior Line of Pleural Reflection (Costodiaphragmatic Line)
Marks the lower limit of the pleural cavity. Passes laterally and posteriorly from the lower end of the anterior line.
Key Rib Crossings (same on both sides after the starting point)
| Reference Line | Pleura crosses | Lung crosses |
|---|---|---|
| Midclavicular line | 8th rib | 6th rib |
| Midaxillary line | 10th rib | 8th rib |
| Lateral border of erector spinae | 12th rib | 10th rib |
The lung margin is always 2 ribs higher than the pleural margin — this gap represents the costodiaphragmatic recess.
Starting Point
- Right side: from the xiphisternal joint (or behind the xiphoid process)
- Left side: from the 6th costal cartilage, ~2 cm lateral to the midline (matches the end of the left anterior line)
4. Posterior Line of Pleural Reflection (Costovertebral Line)
- Ascends from the end of the inferior line (2 cm lateral to the T12 spine) along the side of the vertebral column
- Reaches a point 2 cm lateral to the spine of C7
- Along this line, the costal pleura becomes the mediastinal pleura
Summary Table
| Line | Landmark | Clinical Note |
|---|---|---|
| Cervical | 2.5 cm above medial 1/3 of clavicle (both sides) | Pneumothorax risk from neck procedures |
| Anterior right | Sternoclavicular joint → midpoint sternal angle → midpoint xiphisternal joint | Right angle — straight |
| Anterior left | Same to 4th CC → cardiac notch → 6th CC, 3 cm from midline | Cardiac notch creates area of cardiac dullness |
| Inferior | 8th rib MCL / 10th rib MAL / 12th rib lateral erector spinae | Pleura extends beyond lung here |
| Posterior | 2 cm lateral to T12 spine → 2 cm lateral to C7 spine | Costal → mediastinal pleura transition |