What is the function of the intercostal muscles?

The intercostal muscles play a crucial role in the mechanics of breathing by facilitating the movement of the thoracic cage. They are located between the ribs and consist of two main groups: the external intercostal muscles and the internal intercostal muscles.

During inhalation, the external intercostal muscles contract, elevating the ribs and expanding the thoracic cavity, which lowers the pressure inside the lungs and allows air to flow in. Conversely, during exhalation, the internal intercostal muscles can contract to help depress the ribs, thus aiding in forcing air out of the lungs. This coordinated action of the intercostal muscles is essential for efficient breathing and maintaining proper respiratory function.

In summary, the primary function of the intercostal muscles is to facilitate the movement of the thoracic cage during breathing, making option B the correct choice.