How the air is exchanged from lungs to blood?

Air exchange from the lungs to the bloodstream takes place through a specialized process known as external respiration. This process includes the following steps:

1. Inhalation: During inhalation, the diaphragm and intercostal muscles contract, causing the chest cavity to expand. This expansion lowers the air pressure in the lungs, drawing in fresh air from the atmosphere through the nose or mouth.

2. Conduction: The inhaled air travels through the respiratory passages, which include the nasal passages, pharynx, larynx, trachea, and bronchi. These structures act as conduits for air movement, allowing it to reach the deeper parts of the lungs.

3. Gas exchange in the alveoli: The bronchi divide into smaller branches called bronchioles, which end in tiny sacs called alveoli. The alveoli are the main sites of gas exchange. They have extremely thin walls lined with capillaries, which are tiny blood vessels.

4. Diffusion of oxygen and carbon dioxide: Oxygen from the inhaled air diffuses across the thin alveolar walls and into the capillaries. Simultaneously, carbon dioxide, a waste gas produced by cellular respiration, diffuses from the capillaries into the alveoli.

5. Exhalation: After gas exchange, the diaphragm and intercostal muscles relax, causing the chest cavity to recoil and reducing its volume. This increase in intrathoracic pressure expels the stale air from the lungs through the respiratory passages and out of the body.

6. Transport of gases by the blood: Oxygen picked up by the capillaries combines with hemoglobin, an oxygen-carrying protein in red blood cells, to form oxyhemoglobin. This oxyhemoglobin is then transported by the bloodstream to body tissues, where oxygen is released. At the same time, carbon dioxide carried by the bloodstream is released from the capillaries into the alveoli to be exhaled.

This continuous process of inhalation, gas exchange in the alveoli, and exhalation ensures a constant supply of oxygen to the body and eliminates waste carbon dioxide, playing a crucial role in maintaining vital functions and supporting overall health.