Lungs

lung The respiratory organ of air-breathing vertebrates. A pair of lungs is situated in the thorax, within the ribcage. Each consists essentially of a thin moist membrane that is folded to increase its surface area. Exchange of oxygen and carbon dioxide takes place between blood capillaries on one side of the membrane and air on the other. The lung is supplied with air through a bronchus. The lungs are covered by a thin tissue layer called the pleura. The same kind of thin tissue lines the inside of the chest cavity -- also called pleura. A thin layer of fluid acts as a lubricant allowing the lungs to slip smoothly as they expand and contract with each breath.

Pleurisy

Pleurisy occurs when the double membrane (pleura) that lines the inside of your chest cavity and surrounds each of your lungs becomes inflamed. Also called pleuritis, pleurisy typically causes sharp pain, almost always when you are inhaling and exhaling.
Pleurisy occurs as a complication of a wide variety of underlying conditions. Relieving pleurisy involves treating the underlying condition, if it's known, and taking pain relievers.