Question 5

Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi).

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College Answer

Better answers included details of the significant structures related to the cervical and mediastinal trachea and bronchi. The lobar branches and bronchopulmonary segments requiring naming to attract full marks. Many answers lacked sufficient detail or contained inaccuracies regarding vertebral levels and key structural relations. Some candidates discussed the general anatomy of the airway, including the larynx, structure of the airways, blood supply and innervation. This did not attract marks.

Discussion

The trachea:

10cm fibrocartilaginous tube stretching from C6 to the sternal angle
- Cervical portion: inferior boundary: imaginary line of the thoracic inlet
- Mediastinal (thoracic) portion: crosses from the anterior mediastinum to the posterior mediastinum
Lined with pseudostratified columnar ciliated epithelium and goblet cells
Superiorly, bordered by the larynx
Posterior relation: oesophagus
Right lateral relations: pleura, lung, and the vagus nerve; azygous vein inferiorly
Left lateral relation: left common carotid and subclavian arteries, arch of the aorta, left recurrent laryngeal nerve
Anterior relations: skin and thyroid superiorly, SVC
Inferior relations: right pulmonary artery
Supplied by the inferior thyroid and bronchial arteries; veins drain to the inferior thyroid plexus.
Innervated by the vagus and T2-6 sympathetic chain

The bronchi:

Dichotomously branching divisions of increasingly smaller tubes, consisting of complete and incomplete cartilaginous rings as well as smooth muscle
- Gen 1-4: bronchi (cartilaginous)
- Gen 5-14: bronchioles (no cartilage)
- Gen 15-18: Respiratory bronchioles (some gas exchange)
- Gen 19-22: alveolar ducts
- Gen 23: alveolar sacs
Supplied by bronchial arteries and pulmonary circulation
Venous drainage into the azygos vein and the accessory hemiazygos vein.
Innervated by the vagus and T2-6 sympathetic fibres

References

Mete, Aslı, and İlknur Hatice Akbudak. "Functional Anatomy and Physiology of Airway." Tracheal Intubation. IntechOpen, 2018.

Hyde, Dallas M., Qutayba Hamid, and Charles G. Irvin. "Anatomy, pathology, and physiology of the tracheobronchial tree: emphasis on the distal airways." Journal of Allergy and Clinical Immunology 124.6 (2009): S72-S77.

Neil, J. Hardie, Walter Gilmour, and F. J. Gwynne. "Anatomy of bronchial tree." British medical journal 1.4079 (1939): 495.

Marchant, Warwick. "Anatomy of the larynx, trachea and bronchi." Anaesthesia & intensive care medicine 6.8 (2005): 253-255.

Knight, Darryl A., and Stephen T. Holgate. "The airway epithelium: structural and functional properties in health and disease." Respirology 8.4 (2003): 432-446.

Sauret, V., et al. "Study of the three‐dimensional geometry of the central conducting airways in man using computed tomographic (CT) images." Journal of anatomy 200.2 (2002): 123-134.

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