Trachea and bronchi

The trachea and bronchi are airways that carry air from the larynx to the alveoli of the lungs. Their structure ensures constant passage of air, its purification, humidification and warming.

Trachea

The trachea is a tube 10–12 cm long and about 2 cm in diameter, located from the level of the VI cervical vertebra to the IV–V thoracic vertebra. Its frame is formed by 16–20 cartilaginous half-rings, open at the back. The posterior wall is soft (membranous part), adjacent to the esophagus, which allows the bolus of food to pass freely.

The mucous membrane of the trachea is lined with ciliated (ciliated) epithelium. The cilia make 15–20 oscillations per second, moving mucus with settled particles up to the larynx - this is mucociliary clearance, the main mechanism for cleaning the airways.

Tracheal bifurcation

At the level of the IV–V thoracic vertebrae, the trachea is divided into right and left main bronchi. The right bronchus is shorter, wider and extends at a smaller angle, so foreign bodies more often end up in the right bronchus.

On the inner surface of the bifurcation there is the carina of the trachea (carina) - a sensitive area, irritation of which causes a powerful cough reflex.

Bronchial tree

The main bronchi are divided according to the following scheme:

• Lobar bronchi: right - 3 (upper, middle, lower), left - 2 (upper, lower)
• Segmental bronchi: 10 on the right, 8–10 on the left
• Lobular bronchi → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveoli

As branching progresses, the cartilaginous rings gradually disappear, and the muscle layer strengthens. Bronchioles are able to narrow (bronchospasm in asthma) and expand, regulating air flow.

Clinical significance

Bronchial asthma is a chronic disease in which the bronchi become hyperreactive: their muscles spasm, the mucous membrane swells, and mucus production increases. Understanding the anatomy of the bronchial tree helps the pulmonologist localize the level of obstruction and select therapy.

Bronchoscopy is an endoscopic examination of the respiratory tract. Knowing the anatomy of the branches, the doctor can specifically examine a specific segmental bronchus or remove a foreign body.

You can trace the path of air from the trachea through the bronchi to the alveoli in Humio - an interactive 3D model of the respiratory tract allows you to consider each level of branching.