The pleura is a membrane that surrounds the lung and consists of two membranes, the parietal and the visceral, which are continuous in the hilum region of the lung. The parietal and visceral membranes delimit, for each lung, an independent cavity fully lined by the mesothelium. Typically, this pleural cavity is virtual, containing only a thin layer of lubricating fluid (pleural fluid), allowing smooth sliding of these two membranes during respiration, preventing friction between the visceral and parietal mesothelium.
The visceral and parietal pleural membranes are usually held together due to decreased pressure in the pleural cavity.
The most basic function of the cell cycle is to duplicate accurately the vast amount of DNA in the chromosomes and then segregate the copies precisely into two genetically identical daughter cells.
