The trachealis is the smooth muscle of the posterior membranous tracheal wall, visible on bronchoscopy as the posterior corrugated wall between the C-shaped cartilage rings. It dynamically modulates tracheal diameter and stiffness during breathing and coughing. In intubation, the trachealis forms the posterior wall of the trachea that the endotracheal tube cuff sits against.
| Origin | Posterior tracheal wall — the trachealis connects the free ends of the C-shaped tracheal cartilages, spanning the posterior membranous tracheal wall from the first tracheal ring to the carina |
|---|---|
| Insertion | Posterior membrane of the trachea, forming the membranous wall; the smooth muscle fibres run transversely and longitudinally between the ends of the C-shaped cartilages |
| Nerve Supply | Vagus nerve (CN X) parasympathetic — triggers bronchoconstriction; Sympathetic via thoracic chain — relaxes the trachealis; Recurrent laryngeal nerve provides motor supply |
| Blood Supply | Inferior thyroid artery (cervical trachea); bronchial arteries (thoracic trachea) |
| Actions | Contraction narrows the tracheal lumen and stiffens the posterior tracheal wall during coughing (increasing airflow velocity for cough efficacy); relaxation allows tracheal diameter increase during forced inspiration; the membranous posterior wall bulges into the tracheal lumen during bronchoconstriction |
|---|
Tracheomalacia involves softening of the tracheal cartilages with reduced structural support, causing the posterior trachealis wall to prolapse anteriorly during expiration and produce expiratory stridor or wheeze. Dynamic bronchoscopy during forced expiration demonstrates the characteristic greater than 50% cross-sectional area collapse. Excessive dynamic airway collapse (EDAC) involves abnormal posterior wall movement without cartilage softening. Tracheal resection for stenosis requires re-anastomosis with the posterior trachealis preserved as a continuous layer with the cartilaginous anastomosis.
Tracheal cartilage softening allows the posterior trachealis to prolapse anteriorly during expiration narrowing the tracheal lumen by more than 50%, producing expiratory stridor and recurrent pulmonary infections; dynamic flexible bronchoscopy confirms collapse and tracheobronchoplasty using posterior splinting with mesh permanently stabilises the malacic segment.
