How Do We Breathe?

Every living creature must breathe in some way. All animal life breathes by taking in oxygen. Man gets his oxygen by taking air into the lungs.
It seems a simple thing for us to breathe. We do not even think about it as we do it. But I involve quite a complicated process when a person breathes in, air passes into the body through a series of tubes called "the upper respiratory tract". This starts with the nose. Here, particles which could be harmful to the lungs are stopped or strained out. The nose also warms the air.

From the nose the air turns down through the "pharynx", or throat. From here, the air goes through two smaller tubes called "bronchi", one of which enters each lung. The lungs are large, soft organs. Around the entire lung is a thin covering called "the pleura!'
The lung tissue is like a fine sponge in some ways. But in the lung there are spaces, or air sacs, and it is here that air is received from the bronchi, the proper gases are used, and unwanted gases are forced out. These air spaces are called "alveoli".

The air we take in contains oxygen, nitrogen, carbon dioxide, and water vapor. These same gases are present in the blood but in different amounts. When a fresh breath is drawn in, there is more oxygen in the alveoli than in the blood. So the oxygen passes through the very thin walls of the blood vessels (capillaries) and into the blood. Carbon dioxide goes from the blood into the air sacs of the lung and is exhaled.

While there is much more to the process of breathing, of course, this is the most vital part of it—the exchange of gases that enables all the cells to obtain oxygen and to get rid of carbon dioxide.

People need oxygen and air to live. People breathe out of their nose and mouth