Mod 6 - Lecture 2 - Lungs and Pleura PDF

Lungs and Pleura Learning Outcomes List the main compartments of the thoracic cavity. Describe the anatomy of the pleural cavities and pleural membranes. Compare and contrast the anatomy of the right and left lungs. Compare and contrast the anatomy of the main bronchi.  The thoracic cavi...

Lungs and Pleura Learning Outcomes List the main compartments of the thoracic cavity. Describe the anatomy of the pleural cavities and pleural membranes. Compare and contrast the anatomy of the right and left lungs. Compare and contrast the anatomy of the main bronchi.  The thoracic cavity The thoracic cavity is divided into three compartments: Right and left polmunary cavities, that contain the lungs and pleurae. A central mediastinum, a compartment intervening between the two pleural cavities, which contains all other thoracic structures. It extends vertically from the superior thoracic aperture to the diaphragm. Pleurae Pleura is a serous sac that consists of two continuous membranes: The visceral pleura — which invests all surfaces of the lungs forming their shiny outer surface The parietal pleura — which lines the pulmonary cavities The pleural cavity — is the potential space between the layers of pleura contains pleural fluid, which lubricates the pleural surfaces and allows the layers of pleura to slide smoothly over each other during respiration. Extensions of Pleura The visceral pleura is continuous with the parietal pleura at the hilum of the lung, where structures making up the root of the lung. The parietal pleura consists of three parts: Costal - covers the internal surfaces of the thoracic wall. It is separated from the internal surface of the thoracic wall by endothoracic fascia. Mediastinal - covers the lateral aspects of the mediastinum Diaphragmatic - covers the superior (thoracic) surface of the diaphragm on each side of the mediastinum, except along its costal attachments (origins) and where the diaphragm is fused to the pericardium Extensions of Pleura The cervical pleura covers the apex of the lung (the part of the lung extending superiorly through the superior thoracic aperture into the root of the neck). The cervical pleura is reinforced by a fibrous extension of the endothoracic fascia, the suprapleural membrane (Sibson fascia)  Extensions of Pleura Pleural reflections are the relatively abrupt lines along which the parietal pleura changes direction as it passes (reflects) from one wall of the pleural cavity to another. Costodiaphragmatic recesses are the potential pleural spaces, pleura-lined “gutters,” which surround the upward convexity of the diaphragm inside the thoracic wall Lungs Lungs are pyramidal in shape: Apex of the lungs are the blunt superior end of the lungs ascending above the level of the 1st and is covered by cervical pleura. The Base is the concave inferior surface of the lung, resting on the diaphragm. Right lung is divided by two horizontal and oblique fissures in three superior, middle, and inferior lobes Left lung is divided by oblique fissure to two superior and inferior lobes  Lungs Lungs have: Three surfaces: Costal Mediastinal diaphragmatic Three borders: anterior, posterior, and inferior. The hilum of the lung is a wedge-shaped area on the mediastinal surface of each lung through which the structures forming the root of the lung pass to enter or exit the lung Tracheobronchial Tree The trachea bifurcates at the level of the sternal angle into right and left main bronchi, passing inferolaterally to enter the lungs at the hila The right main bronchus is wider and shorter and runs more vertically than the left main bronchus. The left main bronchus passes inferolaterally, inferior to the arch of the aorta and anterior to the esophagus and thoracic aorta, to reach the hilum of the lung. The Bronchopulmonary Segments The largest Pyramidal-shaped subdivisions of a lobe of the lung, with their apices facing the lung root and their bases at the pleural surface. Usually 18–20 in number (10 in the right lung; 8–10 in the left lung, depending on the combining of segments). Surgically resectable. Supplied independently by a segmental bronchus and a tertiary branch of the pulmonary artery. Named according to the segmental bronchi supplying them. Bronchi in the Conducting Zone Primary bronchi (main bronchi) R & L Largest bronchi Secondary (lobar) bronchi Three on the right Two on the left Tertiary (segmental) bronchi Bronchioles Little bronchi, less than 1 m m in diameter  The Respiratory Zone Consists of air-exchanging structures Respiratory bronchioles – Branch from terminal bronchioles Lead to alveolar ducts Lead to Alveoli  Arterial supply Bronchial arteries supply blood for nutrition of the structures making up the root of the lungs, the supporting tissues of the lungs, and the visceral pleura. The two left bronchial arteries usually arise directly from the thoracic aorta. The single right bronchial artery may also arise directly from the aorta; however, it commonly arises indirectly, either from posterior intercostal arteries (usually the right 3rd posterior intercostal artery) or from a common trunk with the left superior bronchial artery.  The Bronchial Veins Drain only part of the blood supplied to the lungs by the bronchial arteries. The remainder of the blood is drained by the pulmonary veins. The right bronchial vein drains into the azygos vein. The left bronchial vein drains into the accessory hemi-azygos vein or the left superior intercostal vein. The Pulmonary Lymphatic Plexuses The superficial subpleural lymphatic plexus lies deep to the visceral pleura and drains into the bronchopulmonary lymph nodes in the region of the lung hilum. The deep bronchopulmonary lymphatic plexus is located in the submucosa of the bronchi and in the peribronchial connective tissue. It drains initially into the intrinsic pulmonary lymph nodes. Lymph from both the superficial and deep lymphatic plexuses drains to the superior and inferior tracheobronchial lymph nodes. Lymph from the tracheobronchial lymph nodes passes to the right and left bronchomediastinal lymph trunks terminate on each side at the venous angles. Lymph from the parietal pleura drains into the lymph nodes of the thoracic wall (intercostal, parasternal, mediastinal, and phrenic). Nerves of Lungs and Pleurae Nerve fibers of the pulmonary plexuses are autonomic: Vagal parasympathetic fibers bronchoconstrictive, vasodilator, and secretomotor Sympathetic fibers: Bronchodilator, vasoconstrictor Visceral afferent (sensory for reflex and pain).  Clinical aspects of the Pleurae, Lungs, and Tracheobronchial Tree Pneumothorax and Hemothorax Any Questions?