Question

which of the following muscles increases the volume of the thorax during a normal inhalation? (1) diaphragm (2) external intercostals (3) internal intercostals (4) rectus abdominis multiple choice 2, 4 1, 3 2, 3 3, 4

Explanation:

During normal inhalation, the diaphragm contracts and moves downward, increasing the vertical dimension of the thoracic cavity. The external intercostal muscles also contract, elevating the ribs and increasing the anterior - posterior and lateral dimensions of the thorax. The internal intercostals are mainly involved in forced exhalation, and the rectus abdominis is an abdominal muscle that helps in forced exhalation and trunk flexion, not in increasing thoracic volume during normal inhalation.

Answer:

No option identifier is given in the question format, but the correct muscles are the diaphragm (1) and external intercostals (2). If we had to choose from the given option - like formats: None of the provided options (2,4; 1,3; 2,3; 3,4) are correct. The correct combination should be 1, 2.