Background information respiration | Anatomy | Lower respiratory tract | Tracheobronchial system

Anatomical parts of the tracheobronchial system

The tracheobronchial system is also called the anatomical dead space indicating that no gas exchange takes place from the trachea to the terminal bronchiole. Still airways have an important function warming, moistening and clearing the inspiratory air.

The trachea extends from the larynx into the mediastinum and is reinforced by 16-20 C-shaped rings of cartilage. These rings prevent collapse of the trachea during inspiration. The lack of cartilage in the back of these rings allows for expansion of the esophagus during swallowing.

Like a tree the tracheobronchial system splits into several generations of airways. Branching starts at the carina dividing the trachea into the right and left primary bronchus. They are asymmetrical; the right one being wider, shorter and more vertical than the left. Therefore, foreign bodies are more likely to enter it.

After a short distance the main bronchi separate into secondary or lobar bronchi that in turn branch repeatedly into finer tubes. The successive divisions of the bronchial system are termed as follows:

Two primary bronchi; one right and one left

Five secondary (lobar) bronchi; one to each lobe of each lung, 3 right and 2 left.

Tertiary (segmental) bronchi supplying the bronchopulmonary segments; 10 right and 8 to 10 left

Intralobular bronchioli entering the basic units of the lung, the lobules

Terminal bronchioli occur after about 10 more branchings with 50 to 80 occupying one lobule

Respiratory bronchioli; two or more separating from each terminal bronchiole


Klinke R, Silbernagel S. Lehrbuch der Physiologie. 2001. Thieme: Stuttgart

Shier D, Butler J, Lewis R. Hole's human anatomy and physiology. 2004. McGraw Hill: New York

3-D morphological structures of the tracheobronchial system

This is a 3-D model of the tracheobronchial system. It can be moved horizontally and vertically around two axes as well as enlarged or scaled down. Clicking on the "labelling" button identifies the structures with their correct anatomical terms. You also have the possibility to choose between two different graphic renditions.

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