The Respiratory System

In order to stay alive, the body has to breathe air. We breathe in oxygen and we breathe out carbon dioxide. This process is known as respiration. Breathing happens automatically. Every day, the body breathes about 20,000 times. By the time we reach 70 years old, that's about 600 million breaths. All of this breathing occurs because of the respiratory system, which includes the nose, throat, voice box, wind pipe, and lungs. At the top of the respiratory system, the nostrils bring air into the nose, where it's filtered, warmed, and moistened. Tiny hairs called cilia protect the nasal passageways and other parts of the respiratory tract and filter out dust and other particles that enter the nose through the breathed air. Air can also be breathed in through the mouth. The two airways of the nose and mouth meet up at the pharynx, which is located at the back of the throat. The pharynx carries both food and air and is used for digestion and respiration. One path is for food. This is called the esophagus, which leads on to the stomach. The other side is for air. It's called the trachea. A small flap of tissue called the epiglottis covers the air only passage when we swallow. This stops food and liquid from going into the lungs. The larynx will voice box is located at the top of the trachea. The air only pipe. This is where our vocal cords are. The trachea, or windpipe, which is a two to three centimeter tube, then extends downwards from the bottom of the larynx for about 12 centimeters. The walls of the windpipe are made strong by stiff rings of cartilage that keep it open. The trachea is also lined with tiny hairs. They sweep foreign particles and fluids out of the airway, keeping them from entering the lungs. The windpipe divides into two branches, and each one of these enters one of the two lungs of the body. Each branch resembles the limbs of a tree dividing into smaller, finer branches called bronchioles. The bronchioles end in tiny air sacs called alveoli, which look a bit like grapes. These structures enable fresh air to get to the air sacs, which are surrounded by tiny blood vessels or capillaries. The oxygen passes through these air sacs and travels through the capillary walls into the bloodstream. At the same time, carbon dioxide transfers from the bloodstream into the air sacs, where it gets breathed out of the body. When we exercise, the body needs more oxygen to feed the muscles as they work harder. The body responds by breathing more quickly and deeply. As the cells of the muscles use up more oxygen, lungs have to work harder to keep up the supply. The respiratory system then speeds up to supply the body with much needed oxygen, and also to get rid of the carbon dioxide waste in the system. Over time, exercising also helps our chest cavity to get bigger, which enables the body to increase the amount of air it takes in. More capillaries form around the air sacs, so the body gets better at swapping oxygen and carbon dioxide gases. We can see how the body's respiratory system helps the body to move about. And is influenced by regular and ongoing physical activity as