Table of Contents
Definition and Function of Trachea
The major airway leading from the THROAT to the LUNGS – extends about four and a half inches from the top of the throat to the center of the chest. The sternum (breastbone) in the front and the spine in the back protect the trachea for much of its length.
The front of the trachea arches more than the back, producing an oval rather than round tubular structure with a diameter (from side to side) of about an inch.
The Trachea terminates in two branches, the right main BRONCHUS that goes to the right lung and the left main bronchus that goes to the left lung.
The trachea is made of smooth MUSCLE tissue along the back wall with 16 to 20 C-shaped bands of CARTILAGE running along its length. The cartilage rings give the trachea stability and resistance against the pressure of air flow into and out of the lungs. Thousands of hairlike structures called cilia line the inner layer of the trachea, the tracheal epithelium. The cilia move in wavelike patterns to push secretions and foreign matter, such as dust and particles, out of the airways.
The epithelial cells secrete mucus, which keeps the inner trachea moist. The mucus helps humidify the air as it flows into the lungs, and lubricates the air’s passage. The mucus also traps foreign material so the cilia can sweep it from the airways. Coughing expels air rapidly and forcefully from the lungs, pushing SPUTUM (pulmonary mucus and the debris it contains) into the throat for removal from the body.
For further discussion of the trachea within the context of pulmonary structure and function please see the overview section “The Pulmonary System.”