Topography
It starts at the cricoid cartilage of the larynx, runs ventrally down the neck with the esophagus dorsal and then left of it, and enters the thorax through the thoracic inlet between the first rib and the manubrium. In the mediastinum it diverges ventrally from the spine and divides (bifurcatio tracheae, carina) into the right and left principal bronchi, dorsal to the heart base, at about the 4th–5th intercostal space.
Structure
- Tracheal cartilages: about 35 to 45 hyaline C-shaped rings, open dorsally.
- Trachealis muscle: closes the rings dorsally; in the dog it attaches outside them.
- Principal bronchi: continue into each lung and branch into lobar bronchi.
Clinical relevance
- Tracheal collapse: dorsoventral flattening of the rings in toy breeds (Yorkshire terrier, Pomeranian), with a "goose-honk" cough.
- Endotracheal intubation and tracheostomy: require knowing its diameter and its relation to the esophagus and carotid arteries.
- Radiography: dorsal displacement of the trachea suggests cardiomegaly or a cranial mediastinal mass.
3D model
Schematic shape (illustrative fidelity), placed from landmarks on the skeleton and the scanned organs. It shows topography, not fine morphology.