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.