Pleura << PLUR uh >> is a thin membrane that lines the thoracic cavity (chest cavity) and covers the lungs. The part covering the lungs is called the visceral pleura, or pulmonary pleura. The remaining part, called the parietal pleura, lines the chest wall and covers the diaphragm. The two parts of the pleura unite at the root of the lung, where the bronchus (branch of the windpipe) and blood vessels enter the lung.
In a healthy person, the two parts of the pleura touch. They secrete a trace of watery fluid that lubricates their surfaces. Inflammation of the pleura, a condition called pleurisy, can cause fluid to accumulate between the two pleural surfaces, possibly compressing the lung underneath. If a hole develops in the surface of the lung, air enters the space between the pleural surfaces. This condition, called pneumothorax, may cause the lung to collapse.
See also Lung; Membrane; Pleurisy; Pneumothorax.
