Enlargement of Thoracic Cavity by Diaphragm Contraction

The thoracic cavity is a chamber enclosed by the ribcage and the diaphragm, which is the primary muscle responsible for breathing. The contraction of the diaphragm results in the enlargement of the thoracic cavity, which allows for the inhalation of air.

Function of Diaphragm in Breathing

The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. During inhalation, the diaphragm contracts and moves downwards, increasing the volume of the thoracic cavity. This causes a decrease in air pressure inside the lungs, which results in the inflow of air. In contrast, during exhalation, the diaphragm relaxes and moves upwards, reducing the volume of the thoracic cavity and increasing air pressure, which causes the outflow of air.

Other Muscles Involved in Thoracic Cavity Enlargement

In addition to the diaphragm, the external intercostal muscles also play a role in the enlargement of the thoracic cavity during inhalation. These muscles are located between the ribs and contract to lift the ribs upward and outward, which also increases the volume of the thoracic cavity. However, the internal intercostal muscles, located beneath the external intercostals, are involved in the opposite action, which is the contraction during exhalation to decrease the volume of the thoracic cavity.

Conclusion

In summary, the enlargement of the thoracic cavity is primarily achieved by the contraction of the diaphragm during inhalation. This action decreases air pressure inside the lungs, allowing for the inflow of air. While the external intercostal muscles also contribute to thoracic cavity enlargement, the internal intercostal muscles are involved in thoracic cavity reduction during exhalation.