Thoracic Cavity and Pleura Anatomy

Thoracic Cavity

• The mediastinal pleura covers the sides of the mediastinum and has different relations on the right and left sides.
• It encloses the structures of the root of the lung like a sleeve.
• The pulmonary ligament is a loose, empty double-layer fold of pleura that spans between the esophagus medially and the lung laterally.
• The pulmonary ligament's function is to provide a dead space that allows the distention of the pulmonary veins when the venous return from the lung increases.

Pleural Recesses

• Pleural recesses are arrow spaces of the pleural cavity that are not occupied by the lung except in forced inspiration.
• Each pleural sac has two recesses:
  • Costomediastinal recess: lies between the costal and mediastinal pleurae along the anterior border of the pleura, directly behind the sternum.
  • Costodiaphragmatic recess: lies between the costal and diaphragmatic pleurae along the inferior border of the pleura, at the outlet of the thorax.

Surface Anatomy of the Pleura

• Cervical pleura is represented by a curved line convex upwards, drawn from the junction of the medial and middle thirds of the clavicle to the sternoclavicular joint.
• The highest point of this arch lies about 3 cm above the medial 1/3 of the clavicle.
• Anterior border:
  • Upper part is the same on both sides, descending obliquely downwards and medially from the sternoclavicular joint to the sternal angle.
  • On the right side: it descends vertically to the xiphisternal junction.
  • On the left side: it descends vertically down to the 4th costal cartilage, then deviates laterally to gain the left border of the sternum, and descends vertically to the 6th costal cartilage.