MBBS 1st Year Notes Of Pleura


Pleural cavity

A lung covered in the serous sac is called the pleural cavity


Covering of the lungs is called pleura

It is two types

  1. Visceral pleura = this is the inner layer
  2. Parietal pleura = this is the outer layer

Pleural cavity

  • The space between the visceral pleura and parietal pleura is called the pleural cavity. This is the potential space between the two pleura.

1. Visceral pleura

  • Except for the hilum and along with the attachment of pulmonary ligament, it covers all the surfaces of the lung.
  •  It cannot be separated as it is adherent to the lung surface.

2. Parietal pleura

  • It is thicker than the visceral pleura
  • It lines the wall of the pulmonary cavity.

Subdivision of parietal pleura

  1. Costal pleura
  2. Diaphragmatic pleura
  3. Mediastinal pleura
  4. Cervical pleura

1. Costal pleura

  • It lies the inner surface of the thoracic wall
  • It is loosely attached by a thin layer of loose areolar tissue called endothoracic fascia, which is easily sepratable from the thoracic wall in the case of living beings.

2. Diaphragmatic pleura

  • It covers the upper surface of the diaphragm.

3. Mediastinal pleura

  • It forms the lateral boundary of the corresponding surface of the mediastinum.
  • By its reflection it covers the root of the lung and becomes continuous with visceral pleura.

4. Cervical pleura

  • It covers the apex of the lung.
  • It is covered by the supra pleural membrane.
  • It is clinically important that’s why it should not penetrate while anesthetic needle.

Pulmonary ligament

  • It is a pleural fold that surrounds the root of the lung and extends down as a fold called a pulmonary ligament.
  • The function of the pulmonary ligament
  • Pulmonary vein requires some space when it expands during the increased venous return at the time of exercise. At that moment it provides dead space.
  • It allows the descent of the root of the lung with the descent of the diaphragm during inspiration.

The recess of the pleura

  • The expended regions of the pleural cavity are called a pleural recess.
  • It is essential for lung expansion during the deep inspiration.

it is of two types

  1. Costodiaphragmatic recess
  2. Costomediastinal recess

1. Costodiaphragmatic recess

  • It is located inferiorly between the costal and diaphragmatic pleurae,
  • They are the most dependent part of the pleural cavity, hence fluid of pleural effusion is first collected at these sites.

2. Costomediastinal recess

  • It is located between the costal and mediastinal pleurae and lies between the sternum and costal cartilages.
  • It is the place where changes in tone take place from resonant to dull. This is called the area of superficial cardiac dullness.

Nerve supply of the pleura

Parietal pleura

  • It is developed from the somatopleuric layer of the lateral plate mesoderm that why it is supplied by the somatic nerve.
  • It is sensitive to pain
  • The costal and peripheral part of diaphragmatic pleura = supplied by intercostal nerve
  • The mediastinal and central part of diaphragmatic pleura = supplied by phrenic nerve

Visceral pleura

  • It is developed from the splanchnopleuric layer of lateral plate mesoderm that’s why it is supplied by autonomic nerve.
  • Arises from T2-  T5
  • It is insensitive to pain.

Differentiate between the parietal and visceral pleura

parietal pleura  visceral pleura 
lines the thoracic wall and mediastinum  lines the surface of the lung
develops from the somatopleuric mesoderm develops from splanchnopleuric mesoderm
innervated by the somatic nerve inverted by autonomic nerves
sensitive to pain insensitive to pain