The Anatomy of the Trachea

Human organs, artwork showing the trachea

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In This Article

The trachea, commonly known as the windpipe, is the large tube that delivers air from the upper respiratory tract (the nasal passages, throat, and larynx) to the bronchi (the two large airways that branch off into each lung). In the process, it warms and moisturizes the air and catches debris and microbes before they enter the lungs.The trachea is vulnerable to infections, inflammation, and other stresses that can damage cells. This can lead to conditions like tracheal stenosis, in which the trachea narrows and restricts breathing, and tracheal cancer, an extremely rare form of cancer.

Anatomy

The trachea is part of the lower respiratory tract, along with the lungs, bronchi, bronchioles, and alveoli.

Structure

The trachea is roughly 4 to 5 inches long and 1 inch in diameter. It starts just under the larynx (voice box) and runs down the center of the chest behind the sternum (breast bone) and in front of the esophagus.

The trachea is connected to the larynx via a ring of cartilage known as the cricoid cartilage. As the trachea descends the chest, it is surrounded by 16 to 22 U-shaped rings of cartilage that hold the windpipe open like scaffolding, allowing the flow of air.

The posterior wall of the trachea not covered by cartilage is composed of connective tissue and smooth muscle. The muscle will flex and expand when needed to change the diameter of the trachea.

The trachea ends at the carina, a ridge of cartilage that separates and forms the junction into the bronchi.

Membrane Composition

Lining the trachea are mucosal membranes comprised of epithelial cells, mucus-secreting goblet cells, and hair-like projections called cilia that move foreign particles up and out of the airway. Within these membranes are submucosal glands, which act as companions to goblet cells by secreting water molecules and mucin (the gel-like component of mucus) onto the tracheal lining.

The trachea is traversed by a network of blood vessels and lymphatic vessels. In addition to providing the tissues with oxygen and nutrients, the blood vessels regulate the exchange of heat within the airway. The lymphatic vessels help remove microbes on the surface of the wall of the trachea so they can be isolated and neutralized by the immune system.

Function

The trachea serves as the main passageway through which air passes from the upper respiratory tract to the lungs. As air is pulled into the trachea during inhalations, it is warmed and moisturized before entering the lungs.

Most particles that enter the airway are trapped in the thin layer of mucus on the trachea walls. These are then moved upwards toward the mouth by cilia, where they can be swallowed.

The U-shaped sections of cartilage that line the trachea are flexible and can close and open slightly as the trachealis muscle to the back of the rings either contracts or relaxes. Subtle contractions of the trachea occur involuntarily as part of normal respiration.

However, if a foreign object, liquid, or irritant (like smoke) enters the trachea, the muscles can contract violently, causing coughing to expel the substance.

Contractions can be voluntary as well, as with controlled coughing (used to clear the airways in people with COPD or cystic fibrosis) or the Valsalva maneuver (used to stop rapid heartbeats in people with supraventricular tachycardia).

Associated Conditions 

The trachea, like all parts of the respiratory system, is vulnerable to inhaled substances that can damage tissue and interfere with breathing. Certain infections and diseases can also affect the trachea, undermining its structure and/or function.

Choking

Coughing is the body's way to remove foreign substances from the trachea, throat, or lungs. If an object cannot be dislodged from the trachea, choking can occur. Without enough oxygen to fuel the brain and rest of the body, syncope (fainting), asphyxiation (suffocation), and death may occur.

Emergency interventions, such as the Heimlich maneuver or a tracheostomy, may be needed to clear the trachea of an obstruction. Non-life-threatening obstructions usually can be treated in the emergency room with bronchoscopy, in which a flexible scope is inserted into the throat to locate and remove foreign objects.

Tracheitis

Tracheitis is the inflammation of the trachea that occurs almost exclusively in children. It is most often associated with a bacterial infection that has spread from the upper respiratory tract. The bacteria Staphylococcus aureus is a common culprit.

Tracheitis is especially worrisome in babies and young children because any inflammation of their small windpipes can lead to blockage and, in some cases, asphyxiation.

Stridor (high-pitched wheezing caused by airway obstruction or restriction) is a common symptom of tracheitis. Croup can also accompany.

A potentially life-threatening form of tracheal infection, called epiglottitis, is closely linked to the Haemophilus influenzae type B (Hib) bacteria, although it is less commonly seen today with routine Hib vaccination.

Bacterial tracheitis is typically treated with antibiotics. Severe cases may require intravenous antibiotics as well as intubation and mechanical ventilation to aid with breathing.

Tracheoesophageal Fistula

A tracheoesophageal fistula is an abnormal passageway between the trachea and the esophagus that allows swallowed food to enter the trachea and, from there, the lungs. This can lead to choking, gagging, breathing difficulty, and cyanosis (bluish skin due to the lack of oxygen). Aspiration pneumonia can also occur.

A transesophageal fistula may occur as a result of trauma or cancer, although causes like these are rare. More often, it is the result of a congenital defect that causes the incomplete formation of the esophagus (known as esophageal atresia).

Roughly one of every 4,000 children in the United States is born with tracheoesophageal fistula, which in most cases can be treated with surgery.

Tracheal Stenosis

Whenever the trachea is damaged, scarring can develop and cause the airway to become narrowed. This is known as tracheal stenosis.

Tracheal stenosis can cause stridor and dyspnea (shortness of breath), especially with physical exertion. Causes of tracheal stenosis include:

  • Goiter
  • Large vocal polyps
  • Sarcoidosis
  • Amyloidosis
  • Diphtheria and other severe respiratory infections
  • Wegener's granulomatosis
  • Thyroid cancer
  • Lung cancer
  • Lymphoma of the chest

Between 1% and 2% of people who undergo intubation and mechanical ventilation will develop tracheal stenosis. People who require prolonged ventilation are at greatest risk.

Stenosis may be treated with stents and tracheal dilation. In severe cases, surgery may be required.

Tracheomalacia

Tracheomalacia is an uncommon condition in which the trachea collapses on itself during breathing and with coughing. It often is a result of prolonged intubation. It is also an underrecognized complication of chronic obstructive pulmonary disease (COPD), caused by the progressive deterioration of tracheal cartilage caused by chronic inflammation and coughing.

Tracheomalacia can also affect newborns as a result of congenital weakness of tracheal cartilage. Symptoms include stridor, rattling breath sounds, and cyanosis.

Acquired tracheomalacia may require surgery to correct and support the weakened airway. Congenital tracheomalacia rarely requires surgery and usually resolves on its own by the time the child is 2.

Tracheal Cancer

Tracheal cancer is extremely rare, occurring at a rate of approximately one case per every 500,000 people. Most are squamous cell carcinomas caused by cigarette smoking.Cancers that originate in nearby structures, such as the lungs, esophagus, or thyroid gland, can sometimes metastasize (spread) to the trachea.

Benign tumors, including chondromas and papillomas, can also develop in the trachea. Though benign, these can still block airways, affect breathing, and trigger stenosis.

The surgical removal of a tracheal tumor is the preferred method of treatment (with or without radiation therapy). Some people may be able to be treated with radiation alone. Chemotherapy with radiation often is used if a tumor cannot be removed.

Treatment and Rehabilitation

Injuries, infections, and diseases of the trachea can cause damage to the airway, sometimes irreparably. Tracheal stenosis is one such case in which the development of fibrosis (scarring) is most often permanent.Once the underlying cause of a tracheal injury is treated, efforts may be made to repair the trachea or support its function.

Chest Physical Therapy

Since most children with tracheomalacia outgrow the condition by the age of 3, treatment efforts will usually be supportive. This not only includes regular lab and imaging tests but also chest physical therapy (CPT) to maintain proper airway clearance.

Techniques involve chest percussion, vibration/oscillation, deep breathing, and controlled coughing. A humidifier and continuous positive airway pressure (CPAP) device may also be recommended.

CPT also may be recommended for adults with tracheomalacia or anyone who experiences chronic airway obstruction or restriction. Regular exercise, 20 to 30 minutes five times weekly, can also help.

Tracheal Dilation and Stent Placement

In certain cases of tracheal stenosis, a flexible, tube-like instrument called a bougienage may be inserted into the trachea during a bronchoscopy and expanded with a balloon to dilate the airway. A rigid silicone or metal sleeve, called a stent, is then inserted to hold the trachea open.

Tracheal dilation and stent placement are typically used when surgery isn't possible. Most procedures can be done on an outpatient basis and only require a short-acting anesthetic like propofol.

Stent placement can be used on its own in adults with tracheomalacia if conservative therapies fail to provide relief. With that said, it tends to be less effective due to the "floppiness" of the trachea. Airway infection and stent migration are common.

Ablation Therapy

Stenosis can often be treated by destroying retracted scar tissue that causes the narrowing of the airway. The procedure, called ablation, can release the retracted tissue and improve breathing.

Ablative techniques include laser therapy (using a narrow beam of light), electrocautery (using electricity), cryotherapy (using cold), brachytherapy (using radiation), and argon plasma (using argon gas).

Ablation therapies usually can be performed on an outpatient basis with a mild, short-acting sedative and tend to be successful, although pain, cough, and infection are possible.

Fistula Repair

Tracheoesophageal fistulas almost always require surgical repair to close the hole between the trachea and the esophagus. Although tracheal stenting is sometimes used to plug the gap, the stent can slip and require repositioning or replacement.

Surgery is a more permanent solution. Depending on the location of the fistula, a thoracotomy (an incision between the ribs) or cervicotomy (an incision in the neck) may be used to enter the trachea. Once the hole is repaired with sutures, a full-thickness skin graft or muscle graft may be used to prevent the reopening of the fistula.

The rate of complications following fistula repair surgery is high—between 32% and 56%). Pneumonia, airway obstruction, wound infection, and reopening of the fistula are the most common concerns.

Tracheal Resection

Tracheal resection and reconstruction (TRR) is an open surgical procedure commonly used to remove tracheal tumors and treat severe post-intubation stenosis or fistulas.

The resection of the trachea involves the removal of a section of the airway, the cut ends of which are then stitched together with sutures. Reconstruction involves the placement of a small piece of cartilage (taken from another part of the body) to rebuild the trachea and keep it well supported.

TRR is considered major surgery and typically requires two to three weeks of recovery. Complications include post-operative stenosis or fistula as well as vocal cord dysfunction.

Tracheal Reconstruction

Techniques such as the Maddern procedure and REACHER technique involve the removal of diseased tissue combined with a full-thickness skin graft from the thigh and are sometimes used to treat stenosis in the upper part of the trachea near the larynx. As opposed to open resection, the Maddern procedure can be performed transorally (through the mouth). The REACHER procedure requires a cervicotomy, but is still faster than a resection and has a far shorter recovery time.

The only downside to these techniques is that not all surgeons know how to perform them. To this end, you may need to seek treatment outside of your immediate area with a specialist ENT-otolaryngologist.

Tracheostomy

A tracheostomy, also known as a tracheotomy, is a surgical procedure in which a breathing tube is inserted into the trachea through an incision in the throat. It is used when intubation through the nose or mouth is not possible or when long-term ventilator support is needed.

A tracheostomy may be indicated when a lung or esophageal tumor causes compression of the trachea and interferes with breathing. A traumatic chest wall injury or epiglottitis may require an emergency tracheostomy. Permanent tracheostomy may be needed in people with a major spinal cord injury who cannot breathe adequately on their own or those with end-stage lung disease.

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