Trachea Anatomy: Cartilage Rings, Mucociliary Clearance & Function

The trachea (windpipe) is a 10–12 cm flexible tube connecting the larynx to the main bronchi. Its design balances patency, protection, and clearance.

Structural Components

• 16–20 C-shaped hyaline cartilage rings (posteriorly incomplete) — prevent collapse during inspiration.
• Trachealis muscle (smooth muscle + fibrous tissue) closes posterior gap — narrows lumen during coughing (↑ flow velocity).
• Adventitia: Connective tissue anchoring to surroundings.

Mucosal Lining: Pseudostratified Ciliated Columnar Epithelium

• Goblet cells: Secrete mucus (traps particles >2–3 μm).
• Ciliated cells: 200–300 cilia/cell; beat 10–20 Hz → mucus escalator (↑ toward pharynx).
• Basal cells: Progenitors for repair.
• Immune cells: Dendritic, mast, lymphocytes in lamina propria.

Mucociliary Clearance

1. Inhaled particles trapped in mucus blanket.
2. Coordinated ciliary beating propels mucus cephalad at ~1–2 cm/min.
3. Swallowed or expectorated.
4. Impaired by: smoking, anesthesia, dehydration, cystic fibrosis, primary ciliary dyskinesia, intubation.

Clinical Relevance

• Tracheostomy: between rings 2–3 or 3–4.
• Tracheomalacia: cartilage softening → dynamic collapse.
• Intubation: cuff pressure 20–30 cmH₂O to prevent ischemic injury.

The trachea isn't just a pipe—it's an active, self-cleaning conduit.