The trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time. It is epithelium lined with column-shaped cells that have hair-like extensions called cilia, with scattered goblet cells that produce protective mucins. The trachea can be affected by inflammation or infection, usually as a result of a viral illness affecting other parts of the respiratory tract, such as the larynx and bronchi, called croup, that can result in a barking cough. Infection with bacteria usually affects the trachea only and can cause narrowing or even obstruction. As a major part of the respiratory tract, when obstructed the trachea prevents air entering the lungs and so a tracheostomy may be required if the trachea is obstructed. Additionally, during surgery if mechanical ventilation is required when a person is sedated, a tube is inserted into the trachea, called intubation.

Structure-

An adult's trachea has an inner diameter of about 1.5 to 2 centimetres (0.59 to 0.79 in) and a length of about 10 to 11 centimetres (3.9 to 4.3 in); wider in males than females.[2] It begins at the bottom of the larynx, and ends at the carina, the point where the trachea branches into left and right main bronchi.[2] The trachea is surrounded by 16 - 20 rings of hyaline cartilage; these 'rings' are 4mm high in the adult, incomplete and C-shaped.[2] Ligaments connect the rings.[3] The trachealis muscle connects the ends of the incomplete rings and runs along the back wall of the trachea.

Function-The trachea is one part of the respiratory tree, that is a conduit for air to pass through on its way to or from the alveoli of the lungs. This transmits oxygen to the body and removes carbon dioxide