Parietal pleural membrane

Q4 The pleura are serous membranes one layer (the visceral pleura) firmly adheres to the surface of the lung and the other (the parietal pleura) adheres to the inner surface of the thoracic wall and diaphragm. The two pleural membranes lie very close together, separated only by a thin him of fluid. This lubricates the pleural surface, allowing the two layers to smoothly slide over each other as the thoracic wall moves. 

The pleura are connective tissue membranes composed of matrix, mesotheli-al cells, and fibroblasts. There are two types of pleural responses benign responses, such as thickening of the matrix, formation of plaques (which may calcify) or effusions, and fluid accumulation in the interpleural spaces between the visceral and parietal pleurae and neoplastic disease, or the malignancy known as mesothelioma. 

The pleural, pericardial, and peritoneal cavities normally contain a small amount of serous fluid that lubricates the opposing parietal and visceral membrane surfaces. Inflammation or infections affecting the cavities cause fluid to accumulate. The fluid may be removed to determine if it is an effusion or an exudate, a distinction made possible by protein or enzyme analysis. The collection procedure is called paracentesis. When specifically apphed to the pleural cavity, the procedure is a thoracentesis if applied to the pericardial cavity, a pericardiocentesis. Paracenteses shordd be performed only by sldlled and experienced physicians. Pericardiocentesis has now been largely supplanted by echocardiography. 

Taken together, these data indicate that left ventricular dysfunction and elevated cardiac filling pressures, hypothyroidism, and nephrotic syndrome/ hypoalbuminemia may all contribute but are not sufficient for the formation and maintenance of large persistent pleural effusion in AL amyloidosis. The incidence of exudative chemistries and the presence of amyloid deposits on pleural biopsies suggest that amyloid infiltrates and disrupts pleural mechanics, inducing fluid secretion and impairing parietal membrane drainage from the pleural space. 

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