Breathing is how humans interact with the world around them. Through the rhythm of breathing, the oxygen-rich air from the outside is carried into the lungs within. This oxygen, without which many metabolic processes in our bodies cannot take place, is then transported by the blood into every single cell.
The route from the nose into the lungs is covered with a thick carpet of fine, oar-like hairs called cilia. These catch small foreign bodies that are breathed in together with the air. The cilia transport these particles out again and ensure that respiratory air always reaches the lungs at the right temperature. These cilia are surrounded by a natural layer of mucus. When we catch a cold, this mucus thickens and it becomes more difficult to breathe. Our bodies attempt to remove this excess mucus by means of coughing and sneezing.