The respiratory system allows air to reach the lungs, from which oxygen enters the blood and circulates to all body cells. This system also removes waste gases from the body and helps prevent disease due to particulate matter.

The respiratory system helps prevent the intake of harmful particles— such as dust, fumes, and mist — through coughing, sneezing, or swallowing.

The respiratory system is made up of the nose, sinuses, lungs, diaphragm and other organs and structures.

This article examines the various parts of the respiratory system, some respiratory conditions, and how a person breathes. It also looks at lung function and the processes of inhalation and exhalation.

Click on the interactive Bodymap below to move around the model and read more about the respiratory system.

The respiratory system is divided into an upper and lower respiratory tract. The upper tract comprises:

  • the nose and nasal cavity
  • the sinuses
  • the pharynx
  • the larynx

The lower respiratory tract includes:

  • the lungs
  • the trachea
  • the diaphragm

The sections below will look at each part of the respiratory system in more detail.

Nose and nasal cavity

Forming the main external opening of the respiratory system, the nose protects the anterior portion of the nasal cavity. The nose is also unique, as it is the only part of the system that is externally visible.

The nasal cavity is the uppermost part of the respiratory system, divided into two by the nasal septum. It is the best entrance for outside air, as hairs and mucus line the inside wall and operate as air cleansers.

Within this hollow space, the air is warmed, moisturized, and filtered before reaching the lungs. The nose prevents dust, mold, and other contaminants from reaching the lungs.


The paranasal (meaning around the nose) sinuses are four paired, hollow spaces above and below the eyes.

Connected to the nose by small openings, they regulate the temperature and humidity of inhaled air. These cavities also give tone to the voice.

Sinuses develop after birth and reach their final size around the age of 20.


The pharynx, or throat, is a versatile muscular tube, shaped like a funnel, that delivers air from the mouth and nose to the trachea, or windpipe. It also connects the nasal and oral cavities with the larynx and esophagus.

The pharynx is key to the respiratory and digestive systems. It allows inhaled air to pass from the nasal cavity to the larynx, trachea, and lungs.

A section of the pharynx called the nasopharynx hosts the epiglottis. This keeps the passage to the esophagus covered, preventing air from entering the digestive system.


The larynx has a dual function in the respiratory system: as an air canal to the lungs (while stopping food and drink from blocking the airway) and as the “voice box” (which contains vocal cords for speech).

The larynx is a 2-inch tube made up of nine cartilage pieces. It connects the pharynx with the trachea and is held together by ligaments, membranes, and fibrous tissue.


The lungs are the primary organs of the respiratory system, as they perform a vital role in breathing: gas exchange.

The air that a person breathes in through the nose and mouth contains oxygen and other gases. Oxygen enters the lungs, then the bloodstream, allowing the body to function normally. However, the lungs also take the carbon dioxide from the blood and release it into the air when a person breathes out.

The grape-like sacs called alveoli in each lung allow the exchange of oxygen and carbon dioxide to take place.


The trachea runs down the neck and upper chest. It is a wide, hollow tube that connects the larynx to the bronchi, or airways, of the lungs.

Its most vital function is to enable airflow to and from the lungs. The fibroelastic membrane expands and contracts during inhalation and exhalation.


The diaphragm is a dome-shaped sheet of muscle located below the lungs. It separates the chest from the abdomen.

The diaphragm operates as the major muscle of respiration and aids breathing. The parasympathetic nervous system regulates the contraction and relaxation of the diaphragm and intercostal muscles.

There are two phases of breathing: in and out.

As a person inhales, the diaphragm contracts and moves downward. The space left in the chest allows the lungs to expand. Muscles in the ribs also help enlarge the chest cavity, pulling the rib cage upward and outward.

Once the lungs expand, air moves in through the nose and mouth. The air travels down the trachea and into the lungs, allowing a person to breathe.

The exchange of oxygen and carbon dioxide occurs before exhalation. When a person exhales, the diaphragm relaxes, the lungs recoil, and the air moves out of the lungs.

Due to the complex nature of the respiratory system, many health conditions can affect it. The following sections will look at some respiratory conditions in more detail.


Asthma is a chronic, long-term inflammatory condition that affects the airways. Symptoms are variable and recurring, including coughing, chest tightness, and shortness of breath.

Among other medications, doctors may prescribe inhalers containing corticosteroids to treat this condition.

According to the Centers for Disease Control and Prevention (CDC), around 7.7% of adults in the United States have asthma.

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a condition that progresses with time and makes it hard to breathe.

People who smoke heavily may experience inflammation of the airways, which makes it difficult for the lungs to inhale and exhale enough air.

Symptoms of COPD include breathlessness, a persistent cough, and frequent chest infections.

Learn about COPD triggers here.


A symptom of bronchitis is an inflammation of the lung airways. When the airways are inflamed, they produce too much mucus, which causes coughing, wheezing, and fatigue.

The two main types of bronchitis are acute and chronic. Chronic bronchitis is a form of COPD.

A doctor may treat bronchitis with antibiotics and recommend that a person drinks plenty of fluids to dilute the thick mucus in the airways.


Sinusitis can cause inflammation of the air cavities within the nose and lead to facial pain, headache, and a blocked or runny nose.

It usually develops due to an infection and is treatable with nasal sprays, fluids, pain relievers, and decongestants.


Bacteria, viruses, and fungi can all cause pneumonia.

Symptoms include a high temperature, a cough, difficulty breathing, and chest pain.

A doctor will usually treat pneumonia with antibiotics. They may also recommend hospitalization for serious cases.

Lung cancer

Lung cancer begins in the lungs but may spread to the lymph nodes or other areas of the body.

There are two types of lung cancer: small cell and non-small cell lung cancer. They require different treatments, which will depend on how far the condition has progressed.

Lung cancer is dangerous because many people do not have any symptoms until the condition is in an advanced stage.

On average, people breathe 10–20 times per minute. This means that having an efficient respiratory system is essential to quality of life.

If the lungs do not exchange oxygen and carbon dioxide efficiently, it can lead to health issues such as shortness of breath and fatigue.

With so many working parts, keeping the respiratory system healthy is important. People can do this by avoiding smoking, eating a healthful diet, and exercising regularly.