The trachea, commonly known as the windpipe, is a component of the respiratory system, serving as the main airway for moving air into and out of the lungs. This semi-rigid tube begins just below the larynx (voice box) and extends down into the chest cavity. The trachea’s primary purpose is to ensure a continuous, unobstructed path for breathing. Its structure and function maintain the body’s ability to sustain respiration and effectively exchange oxygen and carbon dioxide.
The Structure of the Windpipe
The trachea is a cylindrical tube constructed to prevent its collapse during air movement. Its structural support comes from approximately 16 to 20 horseshoe-shaped rings made of hyaline cartilage. These rings are incomplete, resembling the letter ‘C’, and provide rigidity to the front and sides of the airway.
The open, posterior side of the C-rings is bridged by a band of smooth muscle called the trachealis muscle, which lies against the esophagus. This flexible section allows the esophagus to expand when a person swallows food. The trachea terminates at a point called the carina, where it divides into the two main bronchi that lead to the lungs. The entire inner surface is lined with a specialized mucous membrane.
Essential Roles in Respiration
The trachea’s most straightforward function is air conduction, serving as a fixed conduit for air. Its cartilaginous framework keeps the passageway open at all times, ensuring that air flows freely between the upper respiratory tract and the lungs. This constant patency prevents the tube from flattening due to pressure changes during inhalation and exhalation.
A secondary function is airway protection and conditioning, managed by the mucociliary escalator system. The inner lining of the trachea is composed of ciliated cells interspersed with mucus-producing goblet cells. These goblet cells secrete a layer of sticky mucus that traps inhaled dust, debris, and pathogens before they reach the lung tissue.
The hair-like projections, or cilia, beat in a coordinated motion, sweeping the debris-laden mucus upward toward the pharynx. This material can then be swallowed or expelled via coughing. This self-clearing mechanism filters and cleans the air, while also warming and humidifying it before it enters the lungs.
Common Tracheal Disorders
When the trachea is compromised by disease or injury, breathing can become severely restricted. One common ailment is tracheitis, which involves inflammation, often caused by a bacterial infection following a viral illness. This condition is characterized by swelling of the tracheal lining, resulting in a severe, barking cough and breathing difficulties.
Tracheal stenosis is the narrowing of the airway, which restricts the flow of air. This narrowing is often caused by scar tissue developing after prolonged intubation, where a breathing tube caused trauma to the tracheal wall. Symptoms include a high-pitched, noisy breath sound called stridor, shortness of breath, and recurrent respiratory infections.
Another structural concern is tracheomalacia, where the cartilage in the tracheal walls is softer or weaker than normal. This lack of rigidity causes the trachea to partially collapse, particularly during exhalation. This can lead to a persistent cough and difficulty clearing secretions.
A sudden obstruction of the trachea by a foreign body, commonly referred to as choking, is a life-threatening emergency. Objects can become lodged in the airway, blocking the passage of air to the lungs. Immediate intervention is necessary to dislodge the obstruction and restore respiration.
Procedures for Airway Management
Medical professionals utilize several procedures to manage or restore function to a compromised trachea. Endotracheal intubation involves inserting a flexible tube through the mouth or nose, past the vocal cords, and into the trachea. This is a temporary intervention used in emergency situations, during surgery with general anesthesia, or for short-term mechanical ventilation support.
A tracheostomy is a surgical procedure that creates a direct opening in the neck, bypassing the upper airway entirely, with a tube placed directly into the trachea. This method is chosen for patients who require long-term ventilation, have a complete upper airway obstruction, or need to manage secretions safely. Since the tube is positioned below the vocal cords, it is often a more stable alternative to prolonged intubation.
Bronchoscopy is a diagnostic and therapeutic procedure where a thin, flexible tube with a camera is passed down the airway. This allows physicians to visualize the inside of the trachea and bronchi to identify disorders like stenosis or to guide interventions. It is also used to remove foreign bodies or to assist in placing a tracheostomy tube.