Somatopleuric layer of the lateral plate of mesoderm is the layer from which the parietal pleura grows, therefore the somatic nerves supply it and is sensitive to pain:
- Intercoastal nerves supply with the coastal and peripheral part of the diaphragmatic pleura.
- Phrenic nerve supplies the mediastinal and central part of the diaphragmatic pleura.
The visceral pleura grows from splanchnopleuric layer of the lateral plate of mesoderm, thus it’s supplied by the autonomic (sympathetic) nerves (T2 T5) and is insensitive to pain.
Referred pain of pleura: The pain from central diaphragmatic pleura and mediastinal pleura is referred to the neck or shoulder via phrenic nerves (C3, C4, and C5) because skin at these sites has same segmental supply via the supraclavicular nerves (C3, C4, and C5).
Blood Supply and Lymphatic Drainage
Blood supply of parietal pleura is same as that of the thoracic wall and blood supply of the visceral (pulmonary) pleura is same as that of the lung.
Differences Between The Parietal And Visceral Pleurae
Pleurisy or Pleuritic
It’s the inflammation of the parietal pleura. Medically it presents as pain, that is aggravated by respiratory movements and radiates to thoracic and abdominal walls. It’s generally caused by pulmonary tuberculosis. The pleural surface becomes rough because of accumulation of inflammatory exudate. Because of roughening of the pleural surfaces friction takes place between the 2 layers of pleura during respiratory movements. Consequently pleural wipe can be heard with stethoscope on the surface of the chest wall during inspiration and expiration.
The collection of serous fluid, air, blood, and pus in the pleural cavity is called hydrothorax (pleural effusion) pneumothorax, hemothorax, and pyothorax (empyema), respectively.
Normally the pleural cavity includes only 5-10 ml of clear fluid, which lubricates the pleural surfaces to enable their easy movements without friction. The excessive accumulation of fluid in the pleural cavity is known as pleural effusion. It generally happens because of inflammation of pleura. The pleural effusion results in reduced growth of lung on the side of effusion. Medically it can be discovered with reduced breath sounds and dullness on percussion on the site of effusion.
It’s a process by which an excessive fluid is aspirated from the pleural cavity. It’s performed with the patient in sitting position. Normally the needle is added in the 6th intercostal space in the midaxillary line. The needle is inserted into the lower part of the intercostal space along the upper border of the rib to prevent injury to the intercostal nerve and vessels. The needle enters in sequence via skin, superficial fascia, serratus anterior, intercostal muscles, endothoracic fascia, and parietal pleura to make it to the pleural cavity.
Accumulation of air in the pleural cavity is termed pneumothorax.
Spontaneous pneumothorax: As the particular name suggests, in this state, air enters pleural cavity abruptly due the rupture of emphysematous bullae of the lung.
Open pneumothorax: This condition takes place because of stab wounds on the thoracic wall piercing the pleurae, resulting in the communication of air in the pleural cavity together with the outside (atmospheric) air. Therefore, every time when patient inspires, the air is sucked into the pleural cavity. Occasionally the clothes and the layers of thoracic wall combine to create a valve in order that air enters via the wound during inspiration, but can not leave via it. In such conditions, air pressure builds up constantly in the pleural cavity on the injured side which shoves the mediastinum to the opposite(healthy) side. This is referred to as tension pneumothorax. The tension pneumothorax is defined by (a) failure of lung on the affected side, and (b) compaction of lung on the healthy side.