All the cells in our body require energy to carry out diverse functions. The energy comes from the food we eat. Body cells absorb the digested food and use oxygen to release energy from it. The process of releasing energy from food is called respiration. Carbon dioxide and water vapor are formed as by products during the process of respiration. Respiration is a chemical process.
Respiration is often confused with breathing. Breathing is the process of taking in of oxygen-rich air from the environment and giving out carbon dioxide rich air. Breathing is a purely physical process. The organs which are involved in breathing process are called breathing or respiratory organs.
The human respiratory system is made up of the following organs:
In addition to these organs, cheat muscles and diaphragm also help in the breathing process. Let us study the different organs in details.
The nose encloses a nasal cavity which opens to the outside through two nostrils. Air enters the respiratory system through nose or mouth. The nose has thin hairs which filter the air that enters the respiratory system. The inner lining of the nose produces sticky liquid called mucus. Mucus and nasal hair prevent dust particles and germs from entering the respiratory system. The air entering the lungs is moistened, warmed and filtered in the nose. Now you know why it is better to breathe through the nose than to breathe through the mouth. The nasal cavity leads to the funnel shaped pharynx from where the air enters a box-shaped chamber the larynx or the voice-box.
Larynx or the voice-box is also called ‘Adam’s apple’ and is more prominent in men than in women. Larynx has vocal cords that make sound. The opening of the pharynx into the larynx is guarded by a flap-like structure called epiglottis. The opening to the larynx is also kept open except during swallowing. During swallowing this opening is closed by epiglottis to prevent food from entering the windpipe.
3. Windpipe or Trachea:
Trachea or the windpipe is a long, wide tube running through the neck in front of the oesophagus. It is supported by rings of cartilage which prevent it from collapsing. At its lower end the trachea divides into two smaller tubes called the bronchi.
4. Bronchi (Singular Bronchus):
The trachea divides into two bronchi – a right bronchus and a left bronchus, each of which enters the lung on its own side.
Lungs are like two elastic and conical bags. They are very soft and spongy. This is because they contain lot of air. In fact, one human lung weighs less than half kg. Since they are very elastic, they stretch every time you breathe in air and spring back to their normal shape when you breathe out. As the air enters the lungs, blood takes up the oxygen from it and gives out carbon dioxide and water which is breathed out through the nose. Blood carries the oxygen to all parts of the body.
- Mechanism of breathing: Human lungs lie in an air thigh chest cavity which is bounded on the lower side by a muscular partition called diaphragm. The entire process of breathing can be slit into two phases – breathing in and breathing out.
- Breathing in: In this phase, the diaphragm contracts and the volume of the chest cavity increases. The lungs also expand and get filled with air.
- Breathing out: The diaphragm relaxes and reduces the volume of the chest cavity. This squeezes out the air from the lungs.