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The internal intercostal muscles play a significant role during the process of expiration, particularly during forceful exhalation like during exercise or coughing. Their primary function is to depress the ribs, which helps decrease the volume of the thoracic cavity. When these muscles contract, they pull the ribs downward and inward, leading to an increase in intrathoracic pressure. This action facilitates the expulsion of air from the lungs.

Understanding the anatomical positioning and contraction of the internal intercostals clarifies their role in breathing mechanics. While other muscles and movements are involved in respiration, such as the diaphragm and external intercostals for inhalation, the internal intercostals are specifically adapted for aiding expiration by lowering the rib cage.

The other options do not accurately describe the functions related to expiration performed by the internal intercostals. Elevating the ribs and enhancing inhalation are primarily functions of the external intercostal muscles and accessory muscles of respiration. Stabilizing the sternum does not directly relate to the mechanics of respiration but rather involves postural support. Thus, the correct understanding of the internal intercostals reveals their specific action in reducing thoracic volume to assist with effective expiration.