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Mnemonic

Tracheal Structure

A memory aid for the structure of the trachea and why its cartilages are incomplete.

Anatomy Respiratory Thorax Airway and Ventilation
Expansion

Sixteen to twenty C-shaped cartilages, open posteriorly and bridged by the trachealis muscle

Expansion

  • 16 to 20 C-shaped rings of hyaline cartilage
  • Incomplete posteriorly, where the gap is bridged by the trachealis smooth muscle
  • Lined by pseudostratified ciliated columnar epithelium with goblet cells
  • About 10 to 12 cm long and 2 cm wide in the adult
  • Runs from C6 to the carina at T4/T5

The rings hold the airway open against the negative intrathoracic pressure of inspiration, while the posterior gap allows two things: the oesophagus to distend forwards during swallowing, and the trachealis to contract during coughing, narrowing the lumen and increasing the velocity of expelled air.

The posterior membranous wall is also the structure at risk of injury during over-inflation of a tracheal tube cuff or during percutaneous tracheostomy.