ANATOMY OF PLEURA Dr Mujahid Khan Location The

ANATOMY OF PLEURA Dr. Mujahid Khan

Location Ø The pleurae and lungs lie on either side of the mediastinum within the chest cavity § Each pleura has two parts: Ø Parietal layer Visceral layer Ø

Parietal Layer Ø It lines the thoracic wall Ø Covers the thoracic surface of the diaphragm and the lateral aspect of the mediastinum Ø Extends into the root of the neck to line the undersurface of the suprapleural membrane at the thoracic outlet

Visceral Layer Ø It completely covers the outer surfaces of the lungs Ø Extends into the depths of the interlobar fissures

Pleural Cuff Ø The two layers continuous with one another by means of a cuff of pleura Ø This cuff surrounds the structures entering and leaving the lung at the hilum of each lung Ø Pleural cuff hangs down as a loose fold called the pulmonary ligament

Pleural Cavity Ø The parietal and visceral layers are separated from one another by a slitlike space called pleural cavity Ø Clinicians use the term pleural space instead of the anatomic term pleural cavity Ø Pleural cavity contains thin film of tissue fluid called pleural fluid Ø Fluid permits the two layers to move on each other with the minimum of friction

Cervical Pleura Ø Parietal pleura is divided into the region in which it lies or the surface that it covers Ø The cervical pleura extends up into the neck Ø It lines the undersurface of the suprapleural membrane Ø It reaches a level 1 to 1. 5 in. (2. 5 to 4 cm) above the medial third of the clavicle

Costal Pleura § It lines the inner surfaces of: Ø The ribs The costal cartilages The intercostal spaces The sides of the vertebral bodies The back of the sternum Ø Ø

Diaphragmatic Pleura Ø It covers the thoracic surface of the diaphragm Ø In quiet respiration, the costal and diaphragmatic pleurae are in apposition to each other below the lower border of the lung Ø Costal and diaphragmatic pleurae separate in deep inspiration

Costodiaphragmatic Recess Ø The lower area of the pleural cavity into which the lung expands on inspiration is referred to as the costodiaphragmatic recess

Mediastinal Pleura Ø It covers and forms the lateral boundary of the mediastinum Ø It is reflected as a cuff around the vessels and bronchi at the hilum of the lung Ø Then continuous with the visceral pleura Ø Each lung lies free except at the hilum Ø it is attached to the blood vessels and bronchi that constitute the lung root

Mediastinal Pleura Ø During full inspiration the lungs expand fill the pleural cavities Ø During quiet inspiration the lungs do not fully occupy the pleural cavities at four sites Ø The right and left costodiaphragmatic recesses Ø The right and left costomediastinal recesses

Costodiaphragmatic recesses Ø Are slitlike spaces between the costal and diaphragmatic parietal pleurae Ø Separated only by a capillary layer of pleural fluid Ø During inspiration, the lower margins of the lungs descend into the recesses Ø During expiration, the lower margins of the lungs ascend so that the costal and diaphragmatic pleurae come together again

Costomediastinal Recesses Ø Are situated along the anterior margins of the pleura Ø They are slitlike spaces between the costal and the mediastinal parietal pleurae Ø Separated by a capillary layer of pleural fluid Ø During inspiration and expiration, the anterior borders of the lungs slide in and out of the recesses

Nerve Supply Ø The parietal pleura is sensitive to pain, temperature, touch and pressure, and is supplied as follows: Ø The costal pleura is segmentally supplied by the intercostal nerves Ø The mediastinal pleura is supplied by the phrenic nerve Ø The diaphragmatic pleura is supplied over the domes by the phrenic nerve and around the periphery by the lower six intercostal nerves

Nerve Supply Ø The visceral pleura covering the lungs is sensitive to stretch Ø It is insensitive to common sensations such as pain and touch Ø It receives an autonomic nerve supply from the pulmonary plexus

Pleural Fluid Ø The pleural space normally contains 5 to 10 ml of clear fluid Ø It lubricates the opposing surfaces of the visceral and parietal pleurae during respiration Ø The formation of the fluid results from hydrostatic and osmotic pressures between the capillaries Ø The pleural fluid is normally absorbed into the capillaries of the visceral pleura

Pleural Fluid Ø Any condition that increases the production of the fluid or impairs the drainage of the fluid results in the abnormal accumulation of fluid, called pleural effusion Ø The presence of 300 ml of fluid in the costodiaphragmatic recess in an adult is sufficient to enable its clinical detection Ø The clinical signs include decreased lung expansion on the side of the effusion, with decreased breath sounds and dullness on percussion over the effusion

Pleuricy Ø Inflammation of the pleura secondary to inflammation of the lung called pneumonia Ø Pleural surfaces become coated with inflammatory exudate, causing the surfaces to be roughened Ø Produces friction, and a pleural rub Ø It can be heard with the stethoscope on inspiration and expiration

Pleuricy Ø Often the exudate becomes invaded by fibroblasts Ø That lay down collagen and bind the visceral pleura to the parietal pleura Ø Forms pleural adhesions