Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

What rib motion involves lateral expansion during inhalation?

1. Pump handle motion

2. Bucket handle motion

3. Caliper motion

4. Flare motion

The correct answer is: Bucket handle motion

The concept of rib motion during inhalation involves different mechanisms that facilitate breathing. The bucket handle motion specifically refers to the lateral expansion of the ribs as they move. During inhalation, as the diaphragm contracts and moves downward, there’s a simultaneous outward motion of the lower ribs. In this context, the bucket handle motion refers to how the lower ribs, particularly the 8th through 10th ribs, move in a way that resembles the action of a bucket handle being lifted. This movement allows for increased lateral expansion of the chest cavity, enhancing the lung capacity as the air is drawn in. Understanding this mechanism is crucial for comprehending how the thoracic cavity expands and the lungs fill with air. In comparison, the pump handle motion primarily describes anterior-posterior movement at the upper ribs during inhalation. Caliper motion involves the movement of the first rib and is not primarily associated with lateral expansion. Flare motion deals with the motion of the ribs in relation to the body’s posture without emphasizing the lateral expansion aspect during inhalation.