Respiration is a natural process in most living things. In this process, living beings change energy that is locked in molecules of digested food into a form that can be used by the cells. In the proce3ss of respiration, water ad carbon dioxide is produced. The body continuously takes in oxygen and releases carbon dioxide by this process. Intake of air is called inhalation and its expelling out is called exhalation. On an average, an adult breathes 15 to 17 times every minute.
Human beings breathe in and out through nose and mouth. When air enters the nose, it is warmed and moistened before it goes to the lungs. In addition, the nose helps remove small particles of dirt and dust. This air goes into the lungs through the wind pipe. During the process of respiration, bulging of chest is a muscular action. This action is performed by both voluntary and involuntary muscles. In the process of respiration, mainly intercostals muscles and diaphragm take part. In deep breathing, shoulders, neck and muscles of stomach also take part.
Lungs are the most important organs of respiratory system. There are two lungs, both of which lie in the air tight chest or thoracic cavity. The chest cavity and the lungs are covered with a membrane called pleura. Each lung is made of millions of alveoli. Lungs purify the blood coming from the heart by the oxygen which is inhaled and then the carbon dioxide of the blood is exhaled. After being purified, the blood goes back to the heart.
A person’s berating is automatically controlled by the respiratory centre in the brain. This centre is sensitive to the amount of carbon dioxide in the blood. If there is an increase in carbon dioxide, such as during strenuous exercise, the respiratory centre sends more nerve signals to the muscles that control breathing. As a result, the person breathes faster.
The Human Respiratory System