Which muscles assist in expiration?

The correct choice emphasizes the role of specific abdominal muscles during expiration. During the process of breathing, expiration can be both passive and active. In a restful state, expiration is primarily a passive process that occurs due to the elastic recoil of the lungs. However, during active expiration – such as during vigorous exercise or when blowing out air forcefully – certain muscles become important.

The rectus abdominis and internal obliques are key players in this active phase of expiration. They function to increase intra-abdominal pressure and push the diaphragm upwards. This movement decreases the volume of the thoracic cavity and propels air out of the lungs more efficiently.

Understanding the mechanics of breathing reveals that the diaphragm is the primary muscle involved in inspiration rather than expiration. Similarly, the external intercostals also participate mainly in the inhalation process. The scalene and trapezius muscles, along with the serratus and latissimus dorsi, play roles in other movements and functions but are not primarily involved in the active process of expiration.

Thus, recognizing the specific contributions of the rectus abdominis and internal obliques clarifies their crucial role in mechanizing the expiration process.