Respiratory System - Lungs and Pleura

Respiratory System - Lungs and Pleura

• The respiratory system includes the lungs and pleura.
• The thoracic cavity protects the heart, lungs, and major blood vessels.
• It is a conduit for the esophagus.
• It connects with the neck and abdomen.
• The thoracic cavity includes pleural cavities (lungs) and mediastinum (heart and esophagus).
• The thoracic inlet contains the trachea, esophagus, and great blood vessels.
• It connects with the neck and arms.
• The thoracic outlet connects with the abdomen and contains the esophagus and great blood vessels.
• The thoracic wall comprises the skin, fascia, and intercostal muscles (external, internal, and innermost). The serous membranes include the parietal and visceral pleura.
• The lungs are cone-shaped with an apex, base, and three borders (inferior, anterior, and posterior). They also have two surfaces: costal and mediastinal.
• The lungs are separated by the mediastinum.
• Each lung is enclosed in a double-layered pleural membrane (parietal pleura lines the thoracic cavity wall, visceral pleura covers the lungs).
• The lungs have an apex, hilum, and base. The apex extends 1-2 cm above the clavicles, the base sits on the diaphragm, and the right lobe of the liver and the left lobe of the liver, stomach, and spleen are located on the base. The lungs are cone-shaped and have 2 layers of pleura.
• The lung surfaces are costal (immediately adjacent to ribs and in contact with the thoracic wall, smooth with few markings) and mediastinal (adjacent to the mediastinum, contains the hilum and imprints from various organs).
• The lung borders are inferior (separates the base from the costal surface), anterior (separates the costal surface from the medial surface), and posterior (separates the costal surface from the medial).
• Lung roots are short structures in the mediastinum, covered by mediastinal pleura, and visceral pleura reflects onto the lung surface. They are near the hilum. The hilum is the opening on the medial surface of the lung that contains the main bronchus, pulmonary vessels, and lymphatics.
• The lungs have fissures dividing them into lobes: the right lung has three lobes (upper, middle, and lower), and the left lung has two lobes (upper and lower).
• The lingula is located on the left lung.
• The bronchial tree branches from the trachea to the bronchioles, each containing terminal bronchioles.
• Bronchopulmonary segments are segments of the lung with a separate bronchus and pulmonary artery, and they are functionally independent and resectible. Each segment is cone-shaped, smallest, functionally independent regions that can be resected, and pulmonary vein tributaries pass between segments.
• The lungs' vascularization involves the pulmonary arteries (carrying deoxygenated blood) and pulmonary veins (carrying oxygenated blood).
• Lymphatic drainage from the lungs happens via superficial and deep lymphatic plexuses. Superficial plexuses lie deep to visceral pleura, draining lung parenchyma and visceral pleura, while deep plexuses lie in the submucosa of bronchi, draining structures and lymphatic vessels. Lymph from the lungs then goes to the hilar (pulmonary) lymph nodes, tracheobronchial (carinal) nodes, and paratracheal nodes, either to the right lymphatic duct (right lung) or the thoracic duct (left lung).
• The lungs are innervated by the pulmonary plexus (anterior and posterior pulmonary plexuses follow the trachea and bronchial tree).
• Parasympathetic fibers originate from the vagus nerve, and sympathetic fibers originate from the cervical and thoracic sympathetic trunk.
• Lung auscultation relies on understanding lung fissures (and positioning the stethoscope) for accurate assessment of lung sounds in each lobe.
• The pleura features serous membranes, including the parietal pleura (lining the thoracic cavity) and visceral pleura (covering the lungs). The pleura secretes fluid, decreasing resistance and aiding lung movements during breathing.
• The pleural cavity and its recesses (costomediastinal and costodiaphragmatic recesses) allow expansion during inspiration and accommodate fluid.
• The parietal pleura consists of mediastinal, costal, diaphragmatic, and cervical (cupula) parts.
• The visceral pleura covers the lung, enters fissures covering the lobes, and continues onto the parietal pleura at the lung root.
• Pleura vascularization involves internal thoracic arteries, superior phrenic arteries, posterior intercostal arteries, and superior intercostal arteries.
• Bronchial arteries supply the lungs.
• Pleura innervation includes intercostal nerves, phrenic nerves, and others.
• Pleural fluid accumulation (effusion) is a potential clinical concern.
• Images of X-rays, CT scans and cross-sections of lungs may be used to visualize structures in the lungs.