CorpusHuman Anatomy
RespiratoryOrgan part

Carina of trachea

Carina tracheae

Also known as: tracheal bifurcation, carina

The keel-shaped ridge formed by the last tracheal cartilage at the bifurcation of the trachea into the main bronchi, at the level of the sternal angle (T4/T5).

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Overview

Vertebral levelT4/T5 (sternal angle)
Intrabronchial angle≈70° (wide normal range)

Viewed through a bronchoscope, the carina is a sharp anteroposterior ridge separating the openings of the two main bronchi; its mucosa is the most sensitive area of the airway for triggering cough. The angle between the main bronchi averages ≈70° but varies widely.

The inferior tracheobronchial (subcarinal) lymph nodes lie just below it, and the left atrium lies below and in front. Enlargement of either splays the bronchi apart, widening and blunting the carina — an important sign at bronchoscopy and on chest radiographs. The carina lies at T4/T5 in the cadaver but may descend to T6 in the upright living subject during deep inspiration.

Location

At the plane of the sternal angle (T4/T5), just to the right of the midline, behind the ascending aorta and arch.

Anatomy

Relations

Below: subcarinal nodes and the left atrium; anterior: right pulmonary artery and arch of aorta; posterior: oesophagus.

Function

  • Divides the airway and inspired air between the two lungs.
  • Highly sensitive cough receptor zone protecting the bronchi.

Clinical significance

Widened carina

Distortion or widening of the carina suggests subcarinal lymphadenopathy (e.g. lung cancer metastases, lymphoma, sarcoidosis) or left atrial enlargement (mitral stenosis).

Endotracheal tube position

The tip should lie ≈3–5 cm above the carina; a tube advanced too far usually enters the right main bronchus, ventilating only the right lung.

Test yourself

The tracheal bifurcation (carina) lies at approximately which level?
  1. C6 vertebra
  2. Jugular notch
  3. T4–T5 intervertebral disc (sternal angle)
  4. T8 vertebra

Answer: T4–T5 intervertebral disc (sternal angle)

The trachea begins at the lower border of the cricoid cartilage (C6) and bifurcates at the plane of the sternal angle (T4/T5) — slightly lower (down to T6) in the living upright subject during inspiration.

More respiratory system questions

Compiled from standard anatomy and physiology references — see the Respiratory System sources. For education only; not medical advice.