n. the covering of the lungs (visceral pleura) and of the inner surface of the chest wall (parietal pleura). (See illustration.) The covering consists of a closed sac of serous membrane, which has a smooth shiny moist surface due to the secretion of small amounts of fluid. This fluid lubricates the opposing visceral and parietal surfaces so that they can slide painlessly over each other during breathing. —pleuraladj.
Subjects: Medicine and Health.