windpipe

Windpipe, also known as the trachea, is a flexible air passage that extends from the larynx to the bronchi, conducting air to the lungs and helping to protect the lower airway. It is part of the conducting division of the respiratory system and participates in humidifying inspired air and clearing debris through coughing and the mucociliary system.

Anatomy and structure: The trachea lies in the neck and upper chest, anterior to the esophagus. In adults it measures about 12 centimeters in length and about 2 centimeters in diameter. It begins below the cricoid cartilage and ends at the carina, where it divides into the right and left main bronchi. The anterior and lateral walls are reinforced by C-shaped cartilaginous rings that keep the tube open; the open posterior wall contains smooth muscle and elastic tissue (the trachealis muscle) to allow for flexibility during swallowing. The inner lining is respiratory epithelium—pseudostratified ciliated columnar cells with goblet cells—supported by a basement membrane and secreted mucus that is moved upward by cilia as part of the mucociliary escalator.

Blood supply, innervation, and variation: The trachea receives arterial blood from bronchial arteries and other thoracic vessels, and is supplied by autonomic nerves derived from the vagus nerve and sympathetic fibers, which influence airway tone and secretion. Anatomic variations may occur, and the most clinically relevant region for access is the anterior neck.

Clinical relevance: The trachea can be accessed for procedures such as tracheostomy, often performed between the second and third tracheal rings, to bypass upper airway obstruction or to provide ventilation. It is at risk of injury from trauma, prolonged intubation, infections, and tumors, which can cause cough, wheeze, or impaired airflow. Developmental and congenital anomalies are uncommon but can affect caliber and branching.