Trachea

The trachea is an air passage located in the neck and upper chest of humans and other mammals. It connects the larynx above to the main bronchi below. Its primary function is to convey air to the lungs while filtering, humidifying and warming it as it travels.

The trachea is composed of a series of stacked rings of cartilage that are open at the rear, where they are joined by smooth muscle and connective tissue. This structure allows the airway to remain open when air is inhaled, while still permitting food to pass down the esophagus behind it.

Structure

Inside the trachea is a mucous membrane lined with ciliated cells and glandular cells that secrete mucus. The mucus traps dust and microorganisms, while the cilia beat upward toward the larynx, where debris is swallowed or coughed out. This system is known as mucociliary clearance. Smoking and polluted air can damage the cilia, reducing this cleaning function.

Location and anatomy

The trachea begins below the larynx in the neck and extends downward into the chest, where it divides into the right and left main bronchi. The point of division is called the carina. The right bronchus is typically more vertical and wider than the left, so inhaled objects tend to enter the right side. The thyroid gland lies over the upper portion of the trachea.

Medical conditions

The trachea can develop tracheitis (inflammation), tracheal stenosis (narrowing) resulting from injury or prolonged use of a breathing tube, and obstruction from foreign bodies. When breathing is compromised, doctors can perform a tracheostomy—a surgical opening through the neck into the trachea to allow air to pass directly in. Tracheal cancer is rarer than lung cancer.