Wang N S
National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Clin Chest Med. 1998 Jun;19(2):229-40. doi: 10.1016/s0272-5231(05)70074-5.
The lung and heart, the vital organs, have to be protected and also have to move and change volume continuously to function. For the best protection and function of the lung, the thorax is shaped almost like a bellows with the diaphragm as the moving part. Furthermore, the outer surface of the lung and the inner surface of the protective thoracic cage are covered by an elastic, serous, and lubricating membrane to form the pleural cavity. This is almost like inserting a sealed-wet and stretchable-plastic bag between the lung and the thoracic wall and diaphragm to decrease friction. The lubrication is accomplished by the facing mesothelial cells that have bushy-surface microvilli enmeshing hyaluronic acid-rich glycoproteins. The amount of fluid in the pleural cavity is regulated by the hydrostatic-osmotic pressure relationship and pleuro-lymphatic drainage. Excess fluid, large particles, and cells in the pleural cavity are removed through preformed stomas assisted by respiratory movements. The stoma is found only in the anterior lower thoracic wall and diaphragm and is like the drain of a sink. Finally, clinical and subclinical injuries of the pleura appear to occur often. Reactive mesothelial cells constantly repair the damages and keep the pleural cavity open. Without mesothelial cells, the lung cannot function properly and the pleural cavity will be quickly obliterated by fibrosis.
肺和心脏作为重要器官，既要得到保护，又要不断移动并改变容积以发挥功能。为了实现对肺的最佳保护和功能，胸廓的形状几乎像一个风箱，以膈肌作为运动部件。此外，肺的外表面和保护性胸廓的内表面覆盖着一层弹性、浆液性和润滑性的膜，以形成胸膜腔。这几乎就像是在肺与胸壁及膈肌之间插入一个密封的、湿润的且可拉伸的塑料袋，以减少摩擦。润滑是由相对的间皮细胞完成的，这些细胞具有浓密表面微绒毛，包绕着富含透明质酸的糖蛋白。胸膜腔内的液体量由流体静压-渗透压关系和胸膜-淋巴引流调节。胸膜腔内多余的液体、大颗粒和细胞通过预先形成的气孔在呼吸运动的辅助下被清除。气孔仅见于胸廓前下壁和膈肌，就像水槽的排水口。最后，胸膜的临床和亚临床损伤似乎经常发生。反应性间皮细胞不断修复损伤并保持胸膜腔开放。没有间皮细胞，肺就无法正常发挥功能，胸膜腔将很快被纤维化闭塞。
