Role of the Ribs, Internal and External Intercostal Muscles, and the Diaphragm in Ventilation of the Lungs:
Ribs:
The ribs form the framework of the thoracic cage and play a crucial role in ventilation.
During inhalation, the ribs move upwards and outwards, increasing the volume of the thoracic cavity.
This outward movement of the ribs, especially the action of the true ribs and the sternum, contributes to the expansion of the thoracic cavity during inhalation.
Internal Intercostal Muscles:
The internal intercostal muscles are located between the ribs on the inner aspect of the thoracic cage.
During forced exhalation, the internal intercostal muscles contract, pulling the ribs downward and inward.
This movement decreases the volume of the thoracic cavity, aiding in the expulsion of air from the lungs.
External Intercostal Muscles:
The external intercostal muscles are situated between the ribs on the outer aspect of the thoracic cage.
During inhalation, the external intercostal muscles contract, pulling the ribs upward and outward.
This action expands the thoracic cavity, increasing its volume and creating a negative pressure gradient that allows air to flow into the lungs.
Diaphragm:
The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity, separating it from the abdominal cavity.
During inhalation, the diaphragm contracts and flattens, increasing the vertical dimension of the thoracic cavity.
This downward movement of the diaphragm further enlarges the thoracic cavity, creating a vacuum effect that draws air into the lungs.
During exhalation, the diaphragm relaxes and returns to its dome-shaped position, reducing the volume of the thoracic cavity and assisting in the expulsion of air from the lungs.
