Lungs & Pleura
Lungs and Pleura
Lungs
- The primary function of the lungs is to facilitate gas exchange between the body and the external environment.
- The lungs occupy most of the thoracic cage:
- The base of the lung, its inferior concavity, rests on the diaphragm.
- The mediastinum, which is the space between the lungs, houses the heart.
Right lung:
- 3 lobes (superior, middle, inferior)
- 2 fissures:
- HORIZONTAL fissure separates the superior and middle lobes.
- OBLIQUE fissure separates the middle and inferior lobes.
Left lung:
- 2 lobes (superior, inferior)
- 1 fissure:
- OBLIQUE fissure separates the middle and inferior lobes.
The left lung is smaller than the right because the heart lies slightly to the left within the thoracic cage.
Specifically, the heart nestles within the cardiac impression of the left lung, which is visible as the cardiac notch in anterior view.
Membranes:
The lungs are enclosed by the double-layered pleural sac:
- Visceral pleura forms the outermost layer of the lungs
- Parietal pleura lines the pulmonary cavities.
- Pleural cavity lies between the visceral and parietal pleura; it contains a small film of serous fluid that reduces friction between the layers.
Root of lung:
Pulmonary vessels and the bronchi anchor the lung within the mediastinum.
- Medial aspects of lungs.
- Hilum is obliquely shaped area, is lined by the pleural sleeve (aka, mesopneumonium).
Clinical Correlations:
- Pleurisy is infection of the pleura and causes chest pain upon breathing or coughing.
- Pneumothorax occurs when a ruptured pleural sac allows air to enter the thoracic cavity; the lungs collapse due to pressure changes.
- Pleural effusions
- Acute respiratory distress syndrome
Physiology Review