Overview
The trachea (trachea) begins at the cricoid cartilage of the larynx, runs along the ventral neck and enters the thorax through the cranial thoracic aperture. In the mediastinum it runs dorsal to the heart and ends at the tracheal bifurcation, above the heart base, where it divides into the two principal bronchi.
Structure and relations
- Tracheal cartilages: rings of hyaline cartilage open dorsally; the gap between their ends is closed by the trachealis muscle. Annular ligaments join the rings and make the tube flexible.
- Mucosa: ciliated respiratory epithelium that, with mucus, carries inhaled particles back towards the larynx.
- Tracheal bronchus (bronchus trachealis): arises from the right wall of the trachea, cranial to the bifurcation, and ventilates the cranial lobe of the right lung. It is a feature of ruminants and the pig.
- Relations in the neck: the esophagus lies dorsal and then to the left of the trachea; the common carotid arteries, the vagosympathetic trunk and the deep cervical lymph nodes run alongside it. The thyroid lobes rest on its first rings.
Clinical relevance
- Infectious bovine rhinotracheitis: bovine herpesvirus 1 causes necrotic inflammation of the nasal and tracheal mucosa, with fever, nasal discharge and coughing; it predisposes to bacterial pneumonia.
- Tracheal wash: samples for culture of the lower airways are obtained by passing a catheter into the trachea, through the skin of the neck or via the nose.
- Tracheal bronchus: inhaled agents reach the right cranial lobe early, and it is one of the lobes most affected in calf bronchopneumonia.
- Compression: enlarged mediastinal lymph nodes (tuberculosis, lymphoma) or abscesses can compress the trachea or esophagus and cause dyspnoea or bloat.