Anatomy of the Trachea
Basic Structure and Location
The trachea is a fibromuscular tube approximately 12 cm in length that extends from the lower border of the cricoid cartilage to the carina, where it divides into the mainstem bronchi. 1, 2
- The trachea is formed by U-shaped cartilaginous rings anteriorly and is closed posteriorly by the trachealis muscle 3
- It serves as a conduit connecting the larynx to the principal bronchi that lead to the lungs 1
- The structure bulges posteriorly and maintains patency through its cartilaginous framework 3
Key Anatomic Relationships
In adults, the glottis is the narrowest part of the airway, and the posterior glottis supports the tracheal tube during intubation. 4
- The trachea's relationship to surrounding structures is crucial for safe performance of thoracic surgical procedures 5
- Understanding these anatomic relationships has contributed largely to the advancement of airway surgery in recent years 5
- The trachea is intimately related to the esophagus posteriorly, thyroid gland anteriorly, and major vascular structures laterally 5
Functional Anatomy
The trachea performs multiple critical functions beyond simple air conduction 1, 2:
- Air flow regulation: Serves as the primary conduit for inspiration and expiration 2
- Mucociliary clearance: Achieved by kinocilia and goblet cells in the mucosa, and by tracheal glands, forming a mucociliary escalator for airway clearance and pulmonary defense 1, 2
- Humidification and warming: Conditions inspired air before it reaches the lungs 1
- Phonation apparatus: Contributes to voice production 2
Histologic Features
- The tracheal mucosa contains goblet cells and kinocilia that facilitate mucociliary clearance 1
- Tracheal glands contribute to the production of protective mucus 1
- Different types of stem cells reside in the mucosal epithelium and glandular ducts during adult life 1
- Cholinergic chemosensory cells have been recently described in the trachea 1
Clinical Significance
Respiratory symptoms rarely occur until there is 50% narrowing of the trachea, making early detection of pathology challenging. 6
- Movement of oversized or poorly positioned tracheal tubes, or overinflated cuffs, on the posterior glottis and arytenoid cartilages can lead to edema and compromised airflow 4
- Glottic, subglottic, and tracheal edema can cause life-threatening airway compromise 4
- Proper tube positioning requires the tip to be at midtracheal level to avoid mainstem bronchus intubation 6, 3