The respiratory system includes the nose, throat, voice box, windpipe and lungs.
At the top of the respiratory system, the noctrilo bring air to the nose, where its filtered, warmed and moistered. Tiny hairs called cilia protect the nasal passageway and other parts of the respiratory tract, and filter out clust and other particles that enter the nose through the breathed air. Air can also be breathed in thorugh 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 esophagus, wich leads on to the stomach. The other side is for air: it is called the trachea.
A small flap of tissue called epiglothis covers the air only passage the air when we swallow, this stop food and liquid from going into the lungs. The larynx or voice box is located at the top of the trachea, the air only pipe. This is where our vocal cards are. The trachea or windpipe, which is a 2cm to 3cm tube, then extends downwards from the bottom of the larynx for about 12cm. 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 airways, keeping them from antering the lungs. The windpipe divided 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 en 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 weesels 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.