Breathing is a vital process that allows the exchange of gases between the organism and the environment. The human body needs oxygen to survive and, during breathing, this oxygen is absorbed and carbon dioxide, a metabolic waste, is expelled. The breathing mechanism is complex and involves several parts of the respiratory system. Let's understand the process in 10 steps:
1. Inspiration
Inspiration, or inhalation, is the process by which air enters the lungs. This occurs when the intercostal muscles and diaphragm contract, increasing the volume of the chest cavity. As a result, the pressure inside the lungs decreases, allowing air to enter.
2. Passage of air through the upper airways
The inhaled air passes through the nose or mouth, where it is moistened, warmed and filtered of foreign particles. Then the air passes through the pharynx and larynx.
3. Passage of air through the trachea
The trachea is a tube that conducts air from the larynx to the bronchi. It has cartilage rings that keep it open, allowing air to pass through.
4. Distribution of air to the lungs
The bronchi, which are extensions of the trachea, conduct air into the lungs. The bronchi branch into smaller tubes called bronchioles, which in turn branch into even smaller structures called alveoli.
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5. Gas exchange in the alveoli
Gas exchange takes place in the alveoli. Oxygen in the air passes through the thin walls of the alveoli into the blood capillaries, while carbon dioxide passes from the capillaries into the alveoli, where it is exhaled.
6. Transport of oxygen and carbon dioxide
Oxygen is carried in the blood bound to haemoglobin, a protein present in red blood cells. Carbon dioxide is transported primarily as bicarbonate in blood plasma.
7. Use of oxygen in cells
Oxygen is used by the body's cells to produce energy, a process known as cellular respiration. During this process, carbon dioxide is produced as a waste product.
8. Expiration
Exhalation, or exhalation, is the process by which carbon dioxide is removed from the body. This occurs when the intercostal muscles and diaphragm relax, decreasing the volume of the chest cavity. As a result, pressure inside the lungs increases, forcing air out.
9. Regulation of breathing
The rate and depth of breathing are regulated by the central nervous system in response to levels of carbon dioxide and oxygen in the blood.
10. Defense against pathogens and foreign particles
The respiratory system has defense mechanisms that help protect the body against pathogens and foreign particles. This includes the mucus produced in the airways, which helps to capture and remove these particles, and the cilia, which move the mucus out of the lungs.
In short, breathing is a complex process that involves many parts of the respiratory system and is essential for life.
