24.7 The Pleural Cavities and Pleural Membranes

• • The pleural membrane consists of two layers: the parietal pleura and the visceral pleura.
• The thoracic cavity has the shape of a broad cone
• Walls are the rib cage and muscular diaphragm forms the floor
• Two pleural cavities are separated by the mediastinum
• Each lung occupies a single pleaural cavity, lined by a serous membrane, or pleura
• The parietal pleura covers the inner surface of the thoracic wall, the superior surface of the diaphragm, and the surfaces of the mediastinum
• The visceral pleura covers the outer surfaces of the lungs and extends into the fissures between the lobes
• The space between the parietal and visceral pleurae is called the pleural cavity
• Both pleural membranes secrete a small amount of pleural fluid, a moist slippery coating that lubricates
• Inflammation of the pleurae, a condition called pleurisy
• Inflammation of the pleurae, a condition called pleurisy, may cause

  • membranes to produce and secrete excess pleural fluid
  • inflamed pleurae to adhere to one another, limiting movement
• SUMMARY

  • Each lung occupies a single pleural cavity lined by a pleura (serous membrane). The two types of pleurae are the parietal pleura, covering the inner surface of the thoracic wall, and the visceral pleura, covering the lungs. Pleural fluid is secreted by both pleural membranes.
• What is the function of pleural fluid?

  Pleural fluid reduces friction and provides lubrication between the parietal and visceral surfaces during breathing.