Which muscles are primarily responsible for maintaining the position of ribs 1 and 2 during quiet respiration?

The scalenes are primarily responsible for maintaining the position of ribs 1 and 2 during quiet respiration. These muscles are located in the lateral neck and attach to the cervical vertebrae as well as the first and second ribs. During inspiration, the scalenes elevate these ribs, helping to expand the thoracic cavity and facilitate airflow into the lungs. This elevation is especially important for increasing the volume of the upper chest, supporting the respiratory mechanics during quiet breathing.

The internal intercostal muscles are mainly involved in forced expiration rather than quiet breathing. Their role is to depress the ribs during forced exhalation, which is not the primary function needed for maintaining rib position during normal, quiet respiration.

Pectoralis major, although it has some respiratory function, primarily serves as a prime mover for arm movement rather than stabilizing ribs during breathing.

Serratus anterior primarily functions to protract the scapula and assist in movements of the shoulder, rather than playing a direct role in maintaining the position of the upper ribs during quiet respiration.

Thus, the scalenes are essential for stabilizing and elevating the first two ribs during quiet breathing, making them the correct choice for this question.