Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

What type of rib motion is primarily associated with the anterior-posterior expansion during respiration?

1. Pump handle motion

2. Bucket handle motion

3. Caliper motion

4. Flare motion

The correct answer is: Pump handle motion

The type of rib motion that is primarily associated with anterior-posterior expansion during respiration is pump handle motion. This motion refers to the way the upper ribs (especially the 1st to 5th ribs) move during inhalation. As the ribs elevate during this phase of breathing, they pivot around the costovertebral and costotransverse joints, causing a flaring outwards and forwards at the front of the rib cage. This movement increases the thoracic cavity's volume in the anterior-posterior dimension, which is essential for drawing air into the lungs. This pump handle action helps to create a negative pressure in the thoracic cavity, facilitating lung expansion and airflow. Other types of rib motion, such as bucket handle motion, primarily involve lateral expansion rather than anterior-posterior expansion. Bucket handle motion relates to the lower ribs moving away from the midline increasing the transverse diameter of the thoracic cavity. Caliper motion and flare motion are less commonly referenced in this context and typically involve unique movements of the ribs that do not primarily contribute to anterior-posterior expansion during respiration.