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Trachea and Main Bronchi

Trachea et bronchi principales

For medical students2 min readUpdated 2026-10-10

The trachea (trachea) is an unpaired, hollow tubular organ of the respiratory system that serves as a direct continuation of the larynx and conducts air. At the level of the thoracic cavity, it divides into two main bronchi that head toward the respective lungs.

Tracheal DimensionsLength is 9–15 cm, width is 1.5–2.7 cm
Skeletotopy of BifurcationDivision into bronchi occurs at the level of the IV–V thoracic vertebrae
EpitheliumPseudostratified ciliated columnar epithelium with mucous glands
Sexual DimorphismIn males, the inferior margin of the trachea is located lower than in females

Topography and Skeletotopy of the Trachea

The trachea begins at the level of the VI–VII cervical vertebrae, acting as the direct continuation of the larynx (larynx). An interesting anatomical detail is that the position of the inferior margin of this organ depends on sex: in males, it descends slightly lower than in females.

When examining syntopy (relations with neighboring structures), it is important to distinguish between the regions of the organ:

The overall dimensions of the organ average 9 to 15 cm in length, and the transverse diameter (width) ranges from 1.5 to 2.7 cm.

Bifurcation and Comparative Anatomy of the Main Bronchi

Descending into the thoracic cavity at the level of the IV–V thoracic vertebrae, the trachea divides into two branches. This site is called the tracheal bifurcation (bifurcatio tracheae). Internally, at the site of division, a ridge is formed — the tracheal carina (carina tracheae).

From the bifurcation arise the right and left main bronchi (bronchi principales), each having distinct anatomical features.

FeatureRight Main Bronchulus (bronchus principalis dexter)Left Main Bronchulus (bronchus principalis sinister)
DimensionsShorter and widerLonger and narrower
Angle of departureBranches off at a more obtuse angleBranches off at a more acute angle
DirectionMore direct continuation of the tracheaDeviates more sharply to the side
Topography—Passes inferior to the aortic arch (arcus aortae)

Structure of the Tracheal and Bronchial Wall

The wall of the trachea and its branching main bronchi has a specialized structure that ensures constant patency of the lumen and uninterrupted air conduction.

The framework of the tube is formed by hyaline cartilaginous rings/semi-rings (cartilagines tracheales). They are incomplete posteriorly. The posterior wall is formed by the membranous wall (paries membranaceus). It contains smooth muscle fibers that form the trachealis muscle (m. trachealis).

The internal surface of the respiratory tract is lined with a mucous membrane (tunica mucosa). Its main histological feature is the presence of pseudostratified ciliated columnar epithelium, which, together with the secretion of mucous glands (glandulae tracheales, bronchiales), humidifies and cleanses the inhaled air.

Mnemonic

To remember the features of the right bronchus, use the "Straight Tube" rule: the right bronchus is wider, shorter, and forms a more direct continuation of the trachea, branching off at a more obtuse angle.

Frequently asked questions

Which organs and structures are related to the cervical trachea?

In the cervical region, the thyroid gland, esophagus, and vascular and neural structures are related to the trachea.

  • Anteriorly — the isthmus of the thyroid gland, the unpaired thyroid venous plexus (plexus venosus thyroideus impar), in 6–8% of cases the a. thyroidea ima, and pretracheal lymph nodes (nodi lymphatici pretracheales).
  • Laterally — the lobes of the thyroid gland, which embrace the lateral and partially the posterior walls of the trachea.
  • Posteriorly — the anterior wall of the esophagus, to which the membranous part of the trachea is attached. The recurrent laryngeal nerves run in the tracheoesophageal grooves.
How many cartilage semi-rings form the framework of the trachea?

The framework of the trachea is formed by 16 to 20 cartilage semi-rings.

These structures are incomplete rings composed of hyaline cartilage, forming part of the fibro-cartilaginous coat of the organ. Posteriorly lies the membranous wall (paries membranaceus), where the ends of the cartilage rings are connected by bundles of smooth muscle fibers (m. trachealis). Lower down, at the bifurcation level, the trachea transitions into the main bronchi, where the cartilage rings become complete circles.

What tissue layers make up the tracheal wall?

The tracheal wall consists of four tissue layers.

  • Mucosa (tunica mucosa) — lined with pseudostratified ciliated columnar epithelium and contains mucous glands (glandulae tracheales).
  • Submucosa — located beneath the mucous membrane.
  • Fibro-cartilaginous layer — includes hyaline cartilage semi-rings (cartilagines tracheales). Posteriorly lies the membranous wall (paries membranaceus), containing smooth muscle fibers (m. trachealis).
  • Adventitia — the outer connective tissue layer.
Which arteries supply blood to the trachea?

Blood supply to the trachea is provided by branches of several arteries.

  • Inferior thyroid arteries (aa. thyroideae inferiores) — give off tracheal branches (rr. tracheales) to the cervical portion.
  • Unpaired lowest thyroid artery (a. thyroidea ima) — acts as an additional source of blood supply (present in 6–8% of cases).

Mediastinal and bronchial branches (rr. mediastinales, rr. bronchiales) also contribute to the blood supply of the organ.

Where does lymphatic drainage from the trachea and main bronchi go?

Lymphatic drainage from the trachea and main bronchi occurs into the regional lymph node system of the thoracic cavity and neck.

The drainage pathway includes the following groups of nodes:

  • Bronchopulmonary nodes (nodi bronchopulmonales).
  • Tracheobronchial nodes (nodi lymphoidei tracheobronchiales) — divided into superior (superiores) and inferior bifurcation nodes (inferiores).
  • Paratracheal nodes (nodi paratracheales).
  • Mediastinal nodes — anterior and posterior.

Efferent vessels of the paratracheal nodes subsequently form the right and left bronchomediastinal trunks (trunci bronchomediastinales dexter et sinister).

At what level does the trachea begin and end?

The trachea begins at the level of the VI–VII cervical vertebrae (as a continuation of the larynx) and ends at the bifurcation at the level of the IV–V thoracic vertebrae.

Which main bronchus is wider and shorter?

The right main bronchus (bronchus principalis dexter) is shorter and wider compared to the left.

What is located posterior to the trachea?

In both the cervical and thoracic regions, the esophagus lies posterior to the trachea. This is why the posterior wall of the trachea lacks cartilage and is represented by the membranous wall.

What epithelium lines the inside of the trachea?

The internal surface of the trachea is lined with a mucous membrane featuring pseudostratified ciliated columnar epithelium and numerous mucous glands.

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