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Respiration is a permanent process that never stops because the amount of air within our lungs must remain constant. This mechanism has specifically adapted organic structures: the respiratory pathways and the lungs.

Even though the structure of the lungs is conditioned to dilate and contract according to the entry or exit or air, the activity of other organs and tissues is needed to facilitate the respiratory process and they all work together.

The attached structures that collaborate in pulmonary ventilation are the diaphragm, intercostal muscles, thorax muscles and abdominal muscles. The entry of air and exit of carbon dioxide from our body is organized by mechanical respiration, which takes place in two stages: inhalation and exhalation. Both allow the air inside the lungs to be constantly replenished with fresh air. 


When we inhale, the diaphragm contracts and changes the shape of the thorax. When we inhale air from our surroundings, the contraction of the diaphragm compresses the abdominal viscera, increasing the size of the thorax, allowing the lungs to inflate with the air that was inhaled. The intercostal muscles also contract and allow the ribs to elevate, increasing thoracic capacity even further.


After inhalation, exhalation automatically follows. When we expel air from our body, the muscles that participate in inhalation relax. The diaphragm regains its original shape and the ribs move down and in.

The lungs contract and the space within the thorax diminishes. Finally, air returns to the outside when it is exhaled by the upper airways.

Resistance of the airways

The walls of the respiratory pathways present a certain degree of resistance to the passage of air from and to the lungs. During inhalation, muscle contractions aid in the expansion of the thorax, this decreases airway resistance to the entry of air. The joint work of the muscles found in this area allows air to follow the correct path.

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