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Respiratory System - Lungs, Pleura

• Basics: A body cavity encompassing major cardiovascular and respiratory structures.

• Functions: Protects heart, lungs, and major vessels; facilitates breathing; serves as a passageway for the esophagus; connects the neck and abdomen.

• Contents: Pleural cavities (enclosing lungs); mediastinum (heart, esophagus).

• Thoracic Inlet: Connecting the thoracic cavity to the neck and arms; contains the trachea, esophagus, and great vessels.

• Thoracic Outlet: Connecting the thoracic cavity to the abdomen; contains the esophagus and great vessels.

• Thoracic Wall: Comprised of intercostal muscles, veins, arteries, nerves, fascia, and skin.

• Shape of Thoracic Cavity: An osteocartilagenous conical cage; has a narrow inlet and a wide outlet.

• Lungs: Separated by the mediastinum; each is enclosed by a double-layered pleural membrane. The parietal pleura lines the thoracic cavity wall, the visceral pleura covers the lung tissue.

• Lung Shape: Cone-shaped; has an apex, base, and three borders (inferior, anterior, posterior). It also has two surfaces (costal and mediastinal).

• Apex: Extends 1-2 cm past the clavicle's point.

• Base: Located on the diaphragm.

• Base Related Structures: Base sits on diaphragm; bordered by the liver on the right and left; also bordered by the stomach and spleen.

• Lung Surfaces: Costal surface is immediately adjacent to the ribs, smooth, and in contact with the thoracic wall. Mediastinal surface lies adjacent to the mediastinum, containing the hilum and impressions of various structures.

• Lung Borders: The inferior border differentiates the base from the costal surface; the anterior border separates the costal and medial surfaces; the posterior border separates the costal from the medial surfaces; a smooth, rounded border.

• Lung Roots: Short tubes situated in the mediastinum; covered by the mediastinal pleura; the pleura reflects onto the lung's surface (visceral pleura).

• Lung Hilum: Located on the medial surface; Contains the main bronchus, two pulmonary veins, and one pulmonary artery, as well as lymphatics and nerves.

• Lung Fissures and Lobes: Right lung has two fissures (oblique and horizontal) and three lobes (upper, middle, lower). Left lung has one oblique fissure and two lobes (upper and lower).

• Lingula: A small, tongue-shaped lobe on the left lung.

• Lung Vascularization: Each lung contains one pulmonary artery (carrying deoxygenated blood) and two pulmonary veins (carrying oxygenated blood).

• Lymphatic Drainage: The superficial plexus lies deep to the visceral pleura, draining the lung parenchyma and visceral pleura. Deep lymphatic plexus is in the submucosa of bronchi and peribronchial tissue, often draining into the intrinsic pulmonary lymph nodes. Lymph from lungs drains into pulmonary and bronchopulmonary (hilar) nodes, then tracheobronchial (carinal) nodes and paratracheal nodes, with the right and left lymphatic drainage proceeding to the right lymphatic duct and thoracic duct, respectively.

• Innervation: Primarily from the pulmonary plexus (a combination of sympathetic and parasympathetic fibers) following the trachea and bronchial tree, anterior portion of the pulmonary plexus is anterior to the root of the lung, while the posterior plexus is found posterior to the root of the lung.

• Pleura: A serous membrane, consisting of two layers, the visceral (inner) and parietal (outer). Visceral pleura adheres directly to the lung; parietal pleura lines the inner thoracic cavity.

• Pleural fluid: Located within the pleural space (the potential space between the visceral and parietal pleura) and serves to reduce friction, allowing the lungs to move smoothly on the inner thoracic cavity.

• Pleural Recesses: The costomediastinal and costodiaphragmatic recesses; these are potential spaces that don't contain the lung typically; Expansion into these spaces occurs only during forced inspiration.

• Pleura Vascularization: Blood vessels supplying the parietal pleura include intercostal arteries, internal thoracic arteries, and superior phrenic arteries.

• Pleural Innervation: Intercostal nerves innervate the costal parietal pleura & the peripheral portion of the diaphragmatic parietal pleura, while phrenic nerves innervate the central part of the diaphragmatic parietal pleura and the mediastinal parietal pleura. Nerve fibers are sensitive to pain

• Pleural Fluid Accumulation: Fluid buildup in the pleural space is called a pleural effusion.