The Pleura

The pleural cavity is a closed space (like the inside of a balloon) within which the lung has grown. As the lung grows into the space, it picks up a layer of pleura (outside of balloon) and this is called the visceral pleura. The remainder of the pleura is called the parietal pleura. Pleura is a membrane that is single celled. Normally it produces a small amount of fluid that fills the gap between the parietal and visceral layers of pleura.
The best way to see the various aspects of the pleura is to examine a cross section of the thorax and a frontal (coronal) section.
This is a cross section through the thorax showing the various parts of the parietal pleura. Notice that the visceral and parietal pleura are continuous at the root of the lung.
    Parts of the parietal pleura. (parietal pleura in blue; visceral pleura in purple)
  • costal
  • mediastinal
This is a frontal or (coronal) section through the thorax showing the various parts of the parietal pleura. Notice again that the visceral and parietal pleurae are continuous at the root of the lung.
    Parts of the parietal pleura. (parietal pleura in blue; visceral pleura in purple)
  • costal
  • mediastinal
  • cervical (cupular)
  • diaphragmatic

The Surface of the Lungs

The lungs fill the pleural cavities and are divided into lobes. The left lung has 2 lobes and the right lung has 3 lobes. The bulk of the lung surface is against the ribs and is called the costal surface. Other surfaces include the diaphragmatic and mediastinal. Each lung also has 3 borders: anterior, posterior and inferior. The lobes can be seen in the two adjacent figures. The costal (lateral) surfaces of the lungs are shown. In both lungs, the superior and inferior lobes are separated by the oblique fissure. In the right lung, the superior lobe is further divided into the superior and middle lobes, which are separated by the horizontal fissure.
The anterior border of the left lung is pushed out by the heart and this notch is called the cardiac notch. If you follow this notch inferiorly, you will find a small lingular lobe.

Root of the Lung

You might ask why the artery is in blue in the diagram. Blue usually represents low oxygen blood and the pulmonary arteries contain just that. It is called artery because it is leaving the heart. In turn, red usually represents arteries which have high oxygen content. In this case the pulmonary veins have just picked up oxygen and are therefore oxygen-rich. Veins also return blood to the heart.
    Root of the right lung
  • bronchi lie posterior
  • pulmonary arteries are superior
  • pulmonary veins are inferior and anterior
    Root of the left lung
  • bronchus lies posterior
  • pulmonary artery is superior
  • pulmonary vein is inferior and anterior

Other Relationships With the Root of the Lung

In cadaveric lung specimens, grooves are sometimes left on the mediastinal aspect of the lungs and these are formed by structures near the lung. On the mediastinal surface of the right lung, you will find these structures:
  1. azygos vein and its arch (over the root of the lung)
  2. phrenic nerve anterior to the root of the lung
  3. vagus nerve posterior to the root of the lung
  4. esophagus
On the mediastinal surface of the left lung, you will find these structures:
  1. descending aorta
  2. arch of the aorta over the root of the lung
  3. right common carotid artery
  4. right subclavian artery
  5. phrenic nerve anterior to the root of the lung
  6. vagus nerve posterior to the root of the lung


Pleural Cavity   Pleura


Home
Table of Contents for Thorax
Practice Examination

cadaver