What is Breathing?-Inspiration and Expiration

The act of breathing is essential for all aerobic creatures in order to survive. Cellular respiration is a process where oxygen is taken in and used to produce energy, with carbon dioxide being expelled as a waste product. In order for gas exchange to take place, air must first be brought into the lungs via the act of breathing, or “external respiration”. Once inside the lungs, oxygen diffuses into the alveoli where it can be used by the body.

The pumping of oxygen-containing fresh air into the lungs and pumping of the carbon dioxide-containing air out of the lungs is called breathing. Breathing is a mechanical process. It consists of two phases, inspiration and expiration Breathing occurs rhythmically. The frequency of breathing in a man at rest is 15 to 20 times per minute.

Properties Of Lungs Associated With Breathing

Three properties of the lungs and their associated parts help in breathing

1. Elastic nature of lungs: Lungs are spongy in nature. The lungs themselves can not pull air in or push it out. The passive expansion of elastic lungs takes place during inspiration. Similarly, passive contraction of the lungs takes place during expiration.

2. Diaphragm: The floor of the chest cavity is the diaphragm. It is a muscular sheet. When these muscles relax, the shape of the diaphragm is more dome-like. On the other hand, when the muscles of the diaphragm contract, its shape becomes less dome-like.

3. Chest wall: Walls of the chest cavity are composed of ribs and intercostal muscles. When intercostal muscles between the ribs contract, the ribs are elevated. When these intercostal muscles are relaxed, the ribs settle down.

Inspiration

The moving of the fresh air in the lungs is called inspiration. The space inside the chest cavity is increased during inspiration. This space is increased in two ways: a) The muscles of the ribs contract and elevate the ribs upward and forward.

b) The muscles of the diaphragm also contract and the diaphragm become less domelike These two movements increase the volume of the chest cavity. It reduces pressure in the chest cavity When the pressure in the lungs is decreased, the lungs expand. The expansion of the lungs creates a vacuum in the lungs. There is higher atmospheric pressure outside. So air rushes into the lungs from outside. This is called inspiration.

Expiration

The removal of the consumed chest cavity is reduced in two ways: air from the lungs is called expiration. 55 The space in the a) The intercostal muscles of the ribs are relaxed during expiration. Therefore, the ribs move downward and inward. So the space in the sides of the chest cavity is reduced

b) At the same time, the muscles of the diaphragm are relaxed and the diaphragm becomes more domelike. So the chest cavity is also reduced from the floor This reduction in the space of the chest cavity exerts pressure on the lungs. This pressure Presses the lungs and the air inside the lungs moves out of the lungs. This is called expiration.