All About the Human Respiratory System

The entire respiratory system contains two tracts: the upper respiratory tract and the lower respiratory tract. As the names imply, the upper respiratory tract consists of everything above the vocal folds, and the lower respiratory tract includes everything below the vocal folds.

These two tracts work together to perform respiration, or the process of exchanging carbon dioxide and oxygen between your body and the atmosphere.

From the nose to the lungs, the various elements of the respiratory tract play equally different but important roles in the entire process of respiration.

Upper respiratory tract

The upper respiratory tract begins with the sinuses and nasal cavity, both of which are in the area behind the nose.

• The nasal cavity is the area directly behind the nose that allows outside air into the body. As the air comes through the nose, it encounters cilia lining the nasal cavity. These cilia help trap and dispose of any foreign particles.
• The sinuses are air spaces behind the front of your skull that are located on either side of the nose and along the forehead. The sinuses help to regulate air temperature as you breathe.

In addition to entering through the nasal cavity, air can also enter through the mouth. Once air enters the body, it flows into the lower portion of the upper respiratory system with the pharynx and larynx.

• The pharynx, or throat, allows for the passage of air from the nasal cavity or mouth to the larynx and trachea.
• The larynx, or voice box, contains the vocal folds that are necessary for us to speak and make sounds.

After air enters the larynx, it continues down into the lower respiratory tract, which begins with the trachea.

Lower respiratory tract

• The trachea, or windpipe, is the passage that allows air to flow directly to the lungs. This tube is very rigid and is composed of multiple tracheal rings. Anything that causes the trachea to narrow, such as inflammation or obstruction, will restrict oxygen flow to the lungs.

The primary function of the lungs is to exchange oxygen for carbon dioxide. When we breathe, the lungs inhale oxygen and exhale carbon dioxide.

• In the lungs, the trachea branches off into two bronchi, or tubes, that lead into each lung. These bronchi then continue to branch off into smaller bronchioles. Finally, these bronchioles end in alveoli, or air sacks, that are responsible for the exchange of oxygen and carbon dioxide.

Carbon dioxide and oxygen are exchanged in the alveoli through the following steps:

1. The heart pumps deoxygenated blood to the lungs. This deoxygenated blood contains carbon dioxide, which is a by-product of our everyday cellular metabolism.
2. Once the deoxygenated blood reaches the alveoli, it releases the carbon dioxide in exchange for oxygen. The blood is now oxygenated.
3. The oxygenated blood then travels from the lungs back to the heart, where it’s released back into the circulatory system.

Along with the exchange of minerals in the kidneys, this exchange of carbon dioxide in the lungs is also responsible for helping to maintain the pH balance of the blood.

Bacteria, viruses, and even autoimmune conditions can cause illnesses of the respiratory system. Some respiratory illnesses and conditions only affect the upper tract, while others primarily affect the lower tract.

Upper respiratory tract conditions

• Allergies. There are multiple types of allergies, including food allergies, seasonal allergies, and even skin allergies, that can affect the upper respiratory tract. Some allergies cause mild symptoms, such as runny nose, congestion, or itchy throat. More serious allergies can lead to anaphylaxis and closing of the airways.
• Common cold. The common cold is an upper respiratory tract infection that can be triggered by over 200 viruses. Symptoms of the common cold include runny or stuffy nose, congestion, pressure in the sinuses, sore throat, and more.
• Laryngitis. Laryngitis is a condition that happens when the larynx or vocal cords become inflamed. This condition can be caused by irritation, infection, or overuse. The most common symptoms are losing your voice and throat irritation.
• Pharyngitis. Also known as a sore throat, pharyngitis is inflammation of the pharynx caused by bacterial or viral infections. A sore, scratchy, dry throat is the primary symptom of pharyngitis. This may also be accompanied by cold or flu symptoms such as runny nose, coughing, or wheezing.
• Sinusitis. Sinusitis can be both acute and chronic. This condition is characterized by swollen, inflamed membranes in the nasal cavity and sinuses. Symptoms include congestion, sinus pressure, mucus drainage, and more.

Lower respiratory tract conditions

• Asthma. Asthma is a chronic inflammatory condition that affects the airways. This inflammation causes the airways to narrow, which in turn causes difficulty breathing. Asthma symptoms may include shortness of breath, coughing, and wheezing. If these symptoms become severe enough, they can become an asthma attack.
• Bronchitis. Bronchitis is a condition characterized by inflammation of the bronchial tubes. Symptoms of this condition usually feel like cold symptoms at first, and then turn into a mucus-producing cough. Bronchitis can be either acute (less than 10 days) or chronic (several weeks and recurring).
• Chronic obstructive pulmonary disease (COPD). COPD is an umbrella term for a group of chronic, progressive lung diseases, the most common being bronchitis and emphysema. Over time, these conditions can lead to the deterioration of the airways and lungs. If not treated, they can cause other chronic respiratory illnesses. Symptoms of COPD include:
  • shortness of breath
  • chest tightness
  • wheezing
  • coughing
  • frequent respiratory infections
• Emphysema. Emphysema is a condition that damages the alveoli of the lungs and causes a decrease in the amount of circulating oxygen. Emphysema is a chronic, untreatable condition. The most common symptoms are exhaustion, weight loss, and increased heart rate.
• Lung cancer. Lung cancer is a type of cancer located in the lungs. Lung cancer differs depending on where the cancer is located, such as in the alveoli or airways. Symptoms of lung cancer include shortness of breath and wheezing, accompanied by chest pain, lingering cough with blood, and unexplained weight loss.
• Pneumonia. Pneumonia is an infection that causes the alveoli to become inflamed with pus and fluid. SARS, or severe acute respiratory syndrome, and COVID-19 both cause pneumonia-like symptoms, which are both caused by the coronavirus. This family of viruses has been linked to other severe respiratory infections. If left untreated, pneumonia can be fatal. Symptoms include shortness of breath, chest pain, coughing with mucus, and more.

There are other conditions and illnesses that can affect the respiratory system, but the most common conditions are listed above.

Treatment for respiratory conditions differs depending on the type of illness.

Bacterial infections

Bacterial infections that lead to respiratory conditions require antibiotics for treatment. Antibiotics can be taken as pills, capsules, or liquids.

When you take antibiotics, they’re effective immediately. Even if you begin to feel better, you should always take the full course of antibiotics prescribed to you.

Bacterial infections can include:

• laryngitis
• pharyngitis
• sinusitis
• bronchitis
• pneumonia

Viral infections

Unlike bacterial infections, there’s generally no treatment for viral respiratory diseases. Instead, you must wait for your body to fight off the viral infection on its own. Over-the-counter (OTC) medications can provide some relief from symptoms and allow your body to rest.

The common cold and viral laryngitis, pharyngitis, sinusitis, bronchitis, or pneumonia can take upward of multiple weeks to fully recover from.

Chronic conditions

Some respiratory system conditions are chronic and untreatable. For these conditions, the focus is on managing the symptoms of the illness.

• For mild allergies, OTC allergy medications can help reduce symptoms.
• For asthma, an inhaler and lifestyle changes can help reduce symptoms and flare-ups.
• For COPD, treatments involve medications and machines that can help the lungs breathe easier.
• For lung cancer, surgery, radiation, and chemotherapy are all treatment options.

If you’re experiencing any of the symptoms of bacterial, viral, or chronic respiratory infections, visit your doctor. They can check for signs in your nose and mouth, listen for sounds in your airways, and run multiple diagnostic tests to determine if you have any kind of respiratory illness.

The human respiratory system is responsible for helping provide oxygen to cells, remove carbon dioxide from the body, and balance the pH of the blood.

The upper respiratory tract and the lower respiratory tract both play a crucial role in the exchange of oxygen and carbon dioxide.

When viruses and bacteria enter the body, they can cause illnesses and conditions that lead to inflammation of the respiratory tracts.

If you’re concerned that you have a respiratory illness, visit your doctor right away for a formal diagnosis and treatment.