Trachea Anatomy, Functions, and Conditions

Human organs, artwork showing the trachea

Getty Images / GUSTOIMAGES

The trachea or windpipe is the large air tube that leads from the larynx (the voice box) to the bronchi (the large airways that branch off to enter each lung). It is an important part of the respiratory system that warms and moistens air as well as catches foreign particles and bacteria that are inhaled. While cancer of the trachea is rare, a number of conditions can affect this region, especially the development of tracheal stenosis following intubation. Learn more about the structure of function, as well as how some medical conditions that affect the trachea are diagnosed and treated.

Anatomy

The trachea is roughly 10 to 13 centimeters long in men (4 to 5 inches) and 2.5 centimeters (around 1 inch) in diameter. The trachea is shorter in women. It travels through the chest in close association with many nearby structures, making an in-depth understanding of anatomy essential for surgeons who operate in this region.

Structure

The trachea begins in the neck where it attaches to the larynx (voice box) via a complete ring of cartilage known as the cricoid cartilage. As the trachea descends in the chest, it is surrounded by 16 to 22 U-shaped or "horseshoe-shaped" rings of hyaline cartilage that provide the framework that keeps the trachea from collapsing. With age, this cartilage often becomes calcified.

The back of the trachea that is not covered by cartilage is composed of connective tissue and muscle. The lack of cartilage in this region allows the diameter of the trachea to change during normal respiration, coughing, and the Valsalva maneuver. It also allows the esophagus to distend during swallowing.

Relationship to Other Organs

The trachea lies behind the sternum (breastbone) and in front of the esophagus in the area of the chest between the lungs known as the mediastinum. The beginning of the trachea lies beneath the thyroid gland, with the inferior end connecting with the carina—the area in which the main bronchus separates into two bronchi, one of which enters each lung. Many blood vessels and nerves surround and feed the trachea.

Microscopic Anatomy

The inner lining (mucus membranes) of the trachea is lined with epithelial cells, with goblet cells intermixed.

Function

The trachea serves as a passageway to allow passage of air from the region of the voice box to the main respiratory channels (bronchi) which enter the lungs. As air passes through the trachea it is warmed and moistened. Goblet cells produce mucus that traps particles such as foreign materials, bacteria, and viruses. The entire trachea is lined with cilia, tiny hair-like projections that then move these foreign trapped particles upwards towards the mouth where they can be swallowed.

Medical Conditions 

The trachea can be involved medically in a number of conditions. Some of these include:

Tracheitis

Tracheitis is an infection of the trachea most commonly caused by the bacteria Staphylococcus aureus. It is most common in young children and can make breathing difficult.

Tracheal Foreign Body

When a foreign body is breathed in (aspirated) through the mouth and become lodged in the trachea it is almost always accompanied by choking or coughing. Immediate medical attention is needed to remove the foreign body, often through bronchoscopy. It is most common in young children, but may also occur in the elderly, or those who have a decreased level of consciousness for any reason.

Tracheal Cancer

Cancer of the trachea is very rare. These cancers are most often squamous cell carcinomas and are often related to smoking.

Tracheoesophageal Fistula

Rarely, an abnormal passageway called a fistula may develop between the trachea and esophagus. When this occurs, food that is passing through the esophagus may enter the trachea, and subsequently the lungs. This may occur when a cancer is present, especially cancer of the esophagus which erodes the walls of the trachea allowing this abnormal passageway to develop.

In children, a tracheoesophageal fistula may develop along with the incomplete formation of the esophagus (esophageal atresia). Roughly 1 in 4,000 children are born with this abnormality. Thankfully, this is now very treatable with the help of a skilled pediatric surgical team.

Tracheal Stenosis

When the trachea is damaged, scarring may develop and the trachea may become narrowed (tracheal stenosis). Roughly one percent of people who have an endotracheal tube placed for mechanical ventilation (such as with trauma, respiratory failure, or for surgery with general anesthesia) will develop tracheal stenosis. It is, however, much more common in people who require prolonged ventilation.

Tracheomalacia

Tracheomalacia or tracheobronchomalacia is an uncommon condition in which the trachea collapses on itself during breathing and with coughing. It occurs most often as a complication of chronic obstructive pulmonary disease (COPD) and may also occur as a complication of endotracheal intubation—usually long-term intubation. In children, it may be present from birth as a syndrome with other abnormalities.

Procedures and Tests

Since the trachea cannot be directly visualized, diagnosing disease and treating these conditions when possible requires special tests.

Bronchoscopy

A bronchoscopy is usually the procedure of choice for visualizing the trachea. In this procedure, sedation is given and a tube is placed through the mouth and down into the trachea. If a foreign body is present it may be removed at this time, or other treatments done.

Tracheal Dilation and Stent Placement

With tracheal stenosis, instruments may be placed during a bronchoscopy that dilate the trachea. After the trachea is dilated, a stent may be placed to keep the airway open.

Endotracheal Intubation

When a patient is unable to breathe on her own, as during general surgery, an endotracheal tube may be placed through the mouth and into the trachea. This tube is then connected to a mechanical ventilator to allow for breathing to occur.

Tracheostomy

A tracheostomy is a surgical procedure in which an endotracheal.tube is inserted directly into the trachea. It is used when intubation through the nose or mouth with an endotracheal tube is not possible, or when long-term ventilator support is needed (such as when a person experiences prolonged unconsciousness and coma). Some other conditions for which a tracheostomy may be used include tumors causing obstruction of the windpipe (such as lung cancer or esophageal cancer), epiglottitis, trauma with a chest wall injury, or spinal cord injury. In addition to providing access for ventilation, a tracheostomy can be used to remove secretions from the airways. 

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