Question

What are the muscles involved in expiration?

1) Rectus abdominis
2) Internal intercostals
3) Serratus posterior inferior
4) Transversus thoracis
5) Obliquus externus abdominis

Answer 1

The muscles involved in expiration are the internal intercostal muscles, rectus abdominis, obliquus externus abdominis, transversus thoracis, and serratus posterior inferior. These muscles help in drawing the ribs together, compressing the abdomen, and depressing the ribs, which contribute to the exhalation of air from the lungs.

Step-by-step explanation:

The muscles involved in expiration include:

1. Internal intercostal muscles - these muscles help to draw the ribs together and constrict the rib cage during expiration.
2. Rectus abdominis - part of the abdominal muscles that contract to increase abdominal pressure, which pushes up on the diaphragm and forces air out of the lungs during forced expiration.
3. Obliquus externus abdominis - works with other abdominal muscles to compress the abdomen and assist in forced exhalation.
4. Transversus thoracis - helps to depress the ribs during forced expiration.
5. Serratus posterior inferior - assists in depressing the lower ribs to decrease thoracic volume during active expiration.

Expiration can be a passive or active process depending on the breathing conditions. Normally, during quiet breathing, the process is passive and does not require significant muscular contraction as the lungs recoil from their inspiratory state. However, during forced expiration, as seen during vigorous exercise or coughing, these muscles become more actively involved.