Lung Lobes and Bronchopulmonary Segments

Lung Lobes and Structure

• A lobe is a separate part of an organ with its own blood and nerve supply.
• Lobes can be removed without affecting other parts of the organ.
• Bronchopulmonary segments are further divisions within the lobes.
• Removing a bronchopulmonary segment doesn't affect other segments.
• The left lung typically has two lobes due to the heart's projection on the left side.
• The right lung typically has three lobes.
• The number of lobes is determined embryologically; the right lung forms three branches, and the left forms two.
• Multiple lobes with separate blood vessels and airways may provide functional redundancy if one lobe is blocked.
• Pulmonary embolism events are evidence against the perfect nature of the lobe theory.
• The oblique fissure divides the superior and inferior lobes of the left lung.
• The right lung consists of the upper, middle, and lower lobes.
• The horizontal fissure separates the upper and middle lobes of the right lung; it may not always be clearly defined in cadavers.
• Identifying lungs by overall shape, apex, base, costal surface, and mediastinal surface is key, rather than relying solely on the number of lobes.
• The lung apex extends above the first rib, making it vulnerable to injuries in the shoulder region.
• The liver takes up significant space on the right side, pushing up underneath the right lung and affecting lung expansion.
• The anterior edge of the lung is very thin, maximizing space between the heart and thoracic cage.
• The cardiac notch is a curvature around the left ventricle of the heart.
• The lingula is a tongue-like projection of the left lung that fills space over the inferior part of the heart.
• The upper lobe is easily accessible to the anterior chest for auscultation.
• To listen to the lower lobe you need to listen laterally and posteriorly, lower down the chest.
• The visceral pleura directly covers the lung surface.
• The parietal pleura lines the thoracic cage.

Lung Surfaces Orientation

• The apex is the pointy, superior portion of the lung.
• The base is the diaphragmatic surface of the lung, which is domed and sits on the diaphragm.
• The costal surface is the rounded surface of the lung, showing impressions from the ribs.
• The mediastinal surface is the medial surface of the lung, next to the mediastinum, containing the root or hilum of the lung.

Hilum and Mediastinum

• The hilum (root) of the lung is where the parietal pleura meets the visceral pleura and contains pulmonary arteries, pulmonary veins, and airways.
• Pulmonary arteries carry deoxygenated blood away from the heart to the lungs for oxygenation.
• Pulmonary veins carry oxygenated blood from the lungs back to the heart.
• These colorings are reversed versus what would normally be expected.
• The mediastinum is the connective tissue space containing the heart and great vessels, where the mediastinal surface of the lung connects.
• A clever trick is trying to work out what the structures are at the hilum of the lung.
• How far away from the heart the hilum has been cut will have an impact on identifying structures.

Heart Pluming Knowledge

• The pulmonary trunk leaves the right ventricle of the heart and splits into the left and right pulmonary arteries.
• Pulmonary Arteries are superior when identifying heart structures
• Pulmonary veins return blood from the left side of the heart to the left atrium.
• Pulmonary Veins are Inferior when identifying heart structures.
• The trachea sits Posterior to the the blood vessels but splits into main bronchi.
• Bronchus Location is middling and posterior when identifying lung structures.