Final answer:
The muscles that contract to decrease thoracic cavity dimensions during exhalation are C. transversus thoracis and D. internal intercostals. The diaphragm relaxes during exhalation and does not contribute to the decrease in thoracic volume. Understanding the role of these muscles is crucial for comprehending the mechanics of breathing. Both C & D are correct answers .
Step-by-step explanation:
The student asked which muscles contract to decrease thoracic cavity dimensions during exhalation. During the process of exhalation, certain muscles are activated to decrease the thoracic cavity's volume, thereby increasing internal pressure and pushing air out of the lungs.
The primary muscles responsible for this action are C. transversus thoracis and D. internal intercostals. The transversus thoracis muscles help depress the ribs during forced exhalation, helping to decrease the volume of the thoracic cavity. The internal intercostal muscles are particularly important as they draw the ribs together, constricting the rib cage and thus decreasing the thoracic cavity size during exhalation. It's worth noting that the diaphragm, while a key muscle for inspiration by moving downward and increasing thoracic volume, relaxes during exhalation, but it does not contract to reduce thoracic volume.
Understanding the mechanics of breathing involves knowing how various muscles of the thorax, such as the diaphragm and both sets of intercostal muscles, contribute to the actions of inhalation and exhalation. The external intercostal muscles facilitate inhalation by raising the rib cage and expanding the thoracic cavity. In contrast, during exhalation, the focus shifts to the internal intercostals and transversus thoracis for reducing thoracic volume.