pleura

Pleura is the Greek word for rib or side: πλευρά (pleurá), used by Homer in the Iliad to describe the flank of a warrior struck by a spear. The Hippocratic writers of the 5th and 4th centuries BCE moved the word from the external rib to the membrane lining the chest wall. Pleuritis, inflammation of this membrane, appears in the Hippocratic Epidemics as a recognizable clinical syndrome with fever, chest pain on breathing, and a characteristic friction rub. The diagnosis of pleurisy has been made from those same signs for 2,400 years.

Galen of Pergamon in the 2nd century CE gave the pleura its full anatomical definition, distinguishing the visceral layer covering the lung from the parietal layer lining the chest wall. He described the pleural space between them and noted that injury to this region was dangerous because the cavity communicated with the lung. His texts were translated into Arabic in the 9th-century Baghdad House of Wisdom by Hunayn ibn Ishaq, who kept pleura as the anatomical term throughout. The Arabic medical tradition passed the word back to Latin Europe through translations made at Toledo and Salerno in the 12th century.

Andreas Vesalius of Brussels held the chair of surgery at the University of Padua and published his Fabrica in Basel in 1543, the most rigorous anatomical text yet written. He used pleura exactly as Galen had used it, while correcting dozens of Galenic errors through his own human dissections. The word entered English anatomy in the 16th century without alteration: John Banister's 1578 History of Man used pleura as though no translation were needed. By the 17th century it appeared in English surgical texts describing chest injuries.

The pleural cavity is normally a potential space, not a real one: the two layers of pleura are separated by only 10 to 20 milliliters of lubricating fluid. When air enters this space after a chest injury, the lung collapses in a pneumothorax. When fluid accumulates instead, pleural effusion creates the same pressure from a different source. Chest physicians drain both conditions through the intercostal spaces, piercing the thoracic wall whose ribs Homer first called pleurá.