The mediastinum then, is the space between the right and left pleural sacs.
The arteries of the pleura are derived from the intercostal, internal mammary, musculo-phrenic, thymic, pericardiac, bronchial.
The veins correspond to the arteries.
The Lungs.
—The lungs are the essential organs of respiration. They are two in number, placed one on each side of the chest, separated from each other by the heart and the contents of the mediastinum. A healthy lung hangs free within the pulmonary space. The lung is suspended by the root. The root of the lung is formed by the bronchial tubes, pulmonary artery, pulmonary veins, bronchial arteries, bronchial veins, etc., all of which are enclosed by the reflections of the pleurae.
The root of the lung may be described as being that part where all the great blood vessels and the bronchial tubes, enter the lungs.
In many cases the lung does not hang free, but as a result of former pleurisy, the area of the pulmonary pleura is adherent to the parietal pleura.
Fig. 18—The root of the left lung. (Toldt)