What Are the Lungs and Respiratory System? The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation). This exchange of oxygen and carbon dioxide is called respiration. What Are the Parts of the Respiratory System? The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs. Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified. Tiny hairs called cilia (SIL-ee-uh) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air. The two openings of the airway (the nasal cavity and the mouth) meet at the pharynx (FAR-inks), or throat, at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air. At the bottom of the pharynx, this pathway divides in two, one for food — the esophagus (ih-SAH-fuh-gus), which leads to the stomach — and the other for air. The epiglottis (eh-pih-GLAH-tus), a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs. The larynx, or voice box, is the top part of the air-only pipe. This short tube contains a pair of vocal cords, which vibrate to make sounds. The trachea, or windpipe, is the continuation of the airway below the larynx. The walls of the trachea (TRAY-kee-uh) are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs. At its bottom end, the trachea divides into left and right air tubes called bronchi (BRAHN-kye), which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles (BRAHN-kee-olz). Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each person has hundreds of millions of alveoli in their lungs. This network of alveoli, bronchioles, and bronchi is known as the bronchial tree. The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape and are covered by a thin lining called the pleura (PLUR-uh). The chest cavity, or thorax (THOR-aks), is the airtight box that houses the bronchial tree, lungs, heart, and other structures. The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by a large muscle called the diaphragm (DYE-uh-fram). The chest walls form a protective cage around the lungs and other contents of the chest cavity. How Do the Lungs and Respiratory System Work? The cells in our bodies need oxygen to stay alive. Carbon dioxide is made in our bodies as cells do their jobs. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out. When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward. This makes the chest cavity bigger and pulls air through the nose or mouth into the lungs. In exhalation, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to get smaller and push air out of respiratory system through the nose or mouth. Every few seconds, with each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels) lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells. This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body. In the tiny capillaries of the body tissues, oxygen is freed from the hemoglobin and moves into the cells. Carbon dioxide, made by the cells as they do their work, moves out of the cells into the capillaries, where most of it dissolves in the plasma of the blood. Blood rich in carbon dioxide then returns to the heart via the veins. From the heart, this blood is pumped to the lungs, where carbon dioxide passes into the alveoli to be exhaled. Back to Articles Related Articles Word! Bronchoconstriction Actually, bronchoconstriction affects the airways in a person's lungs. Read More Asthma Center Asthma means breathing problems. Find out what's going on in the lungs and how to stay healthy, if you have it. Read More Movie: Lungs & Respiratory System Watch this movie about the respiratory system, the system that enables you to breathe. Read More Cystic Fibrosis Cystic fibrosis (CF) is a genetic disorder that affects the lungs and digestive system Kids who have it can get lung infections often and have trouble breathing. Read More Cystic Fibrosis Cystic fibrosis (CF) is an inherited disease that causes the body to produce mucus that's extremely thick and sticky. It mainly affects the lungs and the pancreas, causing serious breathing and digestive problems. Read More Kids and Smoking The health risks of smoking are well known, many young people still do it. Here's how to help your kids avoid smoking, vaping, or using chewing tobacco - or quit, if they've already started. Read More Smoking Stinks! Everyone says smoking is bad for you. Why? Find out in this article for kids. Read More Smoking Smoking is on the decline, but some people are still lighting up. Why? The answer is addiction. Find out more in this article for teens. Read More Your Lungs & Respiratory System What's something kids are doing all day, every day? Breathing! Your lungs are large and in charge of breathing, so read all about them in this article. Read More Bronchopulmonary Dysplasia (BPD) Babies who are born prematurely or who experience respiratory problems shortly after birth are at risk for bronchopulmonary dysplasia (BPD), sometimes called chronic lung disease. Read More Pneumonia Pneumonia is a common lung infection that can usually be treated without a hospital stay. Read More Lungs and Respiratory System Each day you breathe about 20,000 times. Find out more about the lungs and breathing process. Read More Croup Croup often causes kids to have a loud cough that sounds like a seal barking. Most cases of croup are caused by viruses, are mild, and can be treated at home. Read More Sinusitis Sinus infections, or sinusitis, are common and easily treated. Read More Bronchiolitis Bronchiolitis is a common illness of the respiratory tract caused by an infection that affects tiny airways. The best treatment for most kids with bronchiolitis is time to recover and plenty of fluids. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.