Human Anatomy
Lungs and Trachea
Lungs and trachea anatomy for MBBS: tracheal bifurcation, bronchi, lobes and fissures, bronchopulmonary segments and lung root, mapped to NMC codes AN24.1 to AN24.6.
MedNext Academy | 3 min read
Lungs and Trachea
Lungs and trachea anatomy for MBBS: tracheal bifurcation, bronchi, lobes and fissures, bronchopulmonary segments and lung root, mapped to NMC codes AN24.1 to AN24.6.
This chapter covers the trachea, bronchi and lungs and the pleura that surrounds them. It details the tracheal bifurcation, why foreign bodies favour the right bronchus, the lobes and fissures, the bronchopulmonary segments and the arrangement of structures at the lung root.
High-yield: Lungs and Trachea
- The trachea begins at the lower border of the cricoid cartilage at C6 and bifurcates at the sternal angle at T4 to T5.
- The carina is the ridge at the tracheal bifurcation and is an important landmark at bronchoscopy.
- The right main bronchus is wider, shorter and more vertical than the left, so inhaled foreign bodies tend to lodge on the right.
- The right lung has three lobes and the left lung has two lobes with a cardiac notch and lingula.
- The oblique fissure separates the lower lobe in both lungs; the horizontal fissure separates the upper and middle lobes on the right.
- Each lung has a bronchopulmonary segment supplied by a segmental bronchus and artery, which can be resected surgically.
- There are ten bronchopulmonary segments in the right lung and about eight to ten in the left.
- The pulmonary arteries carry deoxygenated blood and lie anterosuperior at the hilum on both sides.
- At the right hilum the eparterial bronchus lies uppermost, whereas the pulmonary artery is highest on the left.
- The lungs are covered by visceral pleura, and the parietal pleura lines the chest wall, with the pleural cavity between them.
- The costodiaphragmatic recess is the lowest part of the pleural cavity and is where fluid collects and is aspirated.
- The bronchial arteries from the descending thoracic aorta supply the lung tissue itself.
- The lung root contains the main bronchus, pulmonary artery and veins, bronchial vessels, nerves and lymphatics.
- The apex of the lung rises above the clavicle into the neck and is related to the subclavian vessels.
Lungs and airway at a glance
- **Trachea:** From C6 to the sternal angle (T4 to T5); bifurcates at the carina into right and left main bronchi.
- **Right main bronchus:** Wider, shorter and more vertical; inhaled foreign bodies lodge here more often.
- **Right lung:** Three lobes; oblique and horizontal fissures; ten bronchopulmonary segments.
- **Left lung:** Two lobes; oblique fissure; cardiac notch and lingula; relations to the heart on the left.
NMC competencies in this chapter
- **AN24.1:** Trachea and principal bronchi
- **AN24.2:** External features, lobes and fissures of the lungs
- **AN24.3:** Structures at the root and hilum of the lungs
- **AN24.4:** Bronchopulmonary segments
- **AN24.5:** Blood supply, nerve supply and lymphatic drainage of the lungs
- **AN24.6:** Applied anatomy of the lungs and trachea
Frequently Asked Questions
Why do inhaled foreign bodies lodge in the right bronchus?
The right main bronchus is wider, shorter and more vertical than the left, so it is in a more direct line with the trachea and inhaled objects tend to pass into it more readily.
What is a bronchopulmonary segment?
It is a wedge of lung supplied by its own segmental bronchus and artery. Because segments are functionally and structurally independent, a diseased segment can be removed surgically without affecting its neighbours.
Where does the trachea bifurcate?
The trachea divides into the right and left main bronchi at the level of the sternal angle, which corresponds to the T4 to T5 intervertebral disc. The ridge at the division is the carina.
Where is pleural fluid aspirated?
Fluid collects in the costodiaphragmatic recess, the lowest part of the pleural cavity. A needle is passed here, just above a rib to avoid the neurovascular bundle, to drain a pleural effusion.
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