The traceartes, or winpipe, is a tube that has an inner diameter of about 20-25 mm and a length of about 10-16cm. It commences at the larynx(at the level vertebral level of C6 in humans) and bifurcates into the primary (main) bronchi (at the vertebral level of T4/T5 in humans) in mammals, and from the pharynx to the syrinx in birds, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosae goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards towards their larynx and then the pharynx where it can then be swallowed into the stomach.