Trachea

At a glance

English

Trachea

Latin (TA2)

Trachea

System

Respiratory

Region

Thorax

Side

Single, on the midline

About the trachea

The trachea carries air between the larynx and the lungs. It starts at the lower border of the cricoid cartilage, opposite the sixth cervical vertebra, and descends in the midline through the neck and superior mediastinum to end at the carina, where it splits into the right and left main bronchi. The carina lies roughly opposite the sternal angle, between the fourth and fifth thoracic vertebrae, and moves down a little when breathing in. In an adult the tube is about ten to eleven centimetres long and some one and a half to two centimetres across.

Sixteen to twenty horseshoe-shaped bars of hyaline cartilage, open at the back, keep it from collapsing. Fibroelastic annular ligaments join each ring to the next, and the gap at the back of each ring is closed by the trachealis, a sheet of smooth muscle that narrows the tube during coughing. The rings are springy in youth and may calcify with age, and neighbouring rings sometimes fuse. Inside, the lining is ciliated pseudostratified columnar epithelium with goblet cells and glands. Mucus traps particles and the cilia beat it upwards to the larynx, where it is swallowed or coughed out, a process called mucociliary clearance.

Its relations are clinically vital. In the neck the isthmus of the thyroid gland crosses the second to fourth rings, with the strap muscles and the jugular venous arch in front. The oesophagus lies directly behind it, and the recurrent laryngeal nerves run in the grooves between the two. In the chest the brachiocephalic trunk, left common carotid artery, left brachiocephalic vein and aortic arch lie in front and to the left, with the vagus nerves at its sides.

The trachea can be inflamed by infection, as in croup in children, or narrowed by scarring after prolonged intubation, by a large goitre, by enlarged lymph nodes or by tumours, producing harsh noisy breathing called stridor. Tubes are passed into it for anaesthesia, and when the upper airway is blocked an opening can be made in its front wall below the thyroid isthmus, a tracheostomy. Congenital problems include a fistula between trachea and oesophagus and complete cartilage rings that narrow the lumen.

Function and supply

Begins at

The lower edge of the laryngeal cricoid cartilage, at the level of the sixth cervical vertebra.

Ends at

Ends at the carina, at about the sternal angle, by dividing into the right and left main bronchi.

Function

Conducts air to and from the lungs, keeps the airway open with its cartilage rings, and clears inhaled particles by its mucus and cilia.

Nerve supply

Vagus nerves, largely through the recurrent laryngeal nerves, with sympathetic fibres from the cervical and upper thoracic ganglia.

Blood supply

Inferior thyroid arteries to the upper part and bronchial arteries to the lower part, joined by anastomoses along its sides; veins to the inferior thyroid veins; lymph to pretracheal and paratracheal nodes.