■ Is a thin serous membrane that consists of a parietal pleura and a visceral pleura.
1. Parietal Pleura
■ Lines the inner surface of the thoracic wall and the mediastinum and has costal, diaphragmatic, mediastinal, and cervical parts. The cervical pleura (cupula) is the dome of the pleura, projecting into the neck above the neck of the fi rst rib. It is reinforced by Sibson’s fascia (suprapleural membrane), which is a thickened portion of the endothoracic fascia, and is attached to the fi rst rib and the transverse process of
the seventh cervical vertebra.
■ Is separated from the thoracic wall by the endothoracic fascia, which is an extrapleural fascial sheet lining the thoracic wall.
■ Is innervated by the intercostal nerves (costal pleura and the peripheral portion of the diaphragmatic pleura) and the phrenic nerves (central portion of the diaphragmatic pleura and the mediastinal pleura). The parietal pleura is very sensitive to pain.
■ Is supplied by branches of the internal thoracic, superior phrenic, posterior intercostal, and superior intercostal arteries. However, the visceral pleura is supplied by the bronchial arteries.
■ Forms the pulmonary ligament, a two-layered vertical fold of mediastinal pleura, which extends along the mediastinal surface of each lung from the hilus to the base (diaphragmatic surface) and ends in a free falciform border. It supports the lungs in the pleural sac by retaining the lower parts of the lungs in position.
Visceral Pleura (Pulmonary Pleura)
■ Intimately invests the lungs and dips into all of the fi ssures.
■ Is supplied by bronchial arteries, but its venous blood is drained by pulmonary veins.
■ Is insensitive to pain but is sensitive to stretch and contains vasomotor fi bers and sensory endings of vagal origin, which may be involved in respiratory reflexes.
■ Is a potential space between the parietal and visceral pleurae.
■ Represents a closed sac with no communication between right and left parts.
■ Contains a fi lm of fl uid that lubricates the surface of the pleurae and facilitates the movement of the lungs.
1. Costodiaphragmatic Recesses
■ Are the pleural recesses formed by the refl ection of the costal and diaphragmatic pleurae.
■ Can accumulate fl uid when in the erect position.
■ Allow the lungs to be pulled in and expanded during inspiration.
2. Costomediastinal Recesses
■ Are part of the pleural cavity where the costal and mediastinal pleurae meet.