Rib Cage Movement During Inhalation: A Simple Guide

During inhalation, the thoracic cavity expands through coordinated movements:

1. Ribs and sternum move upward and outward (bucket-handle and pump-handle motions), increasing the anteroposterior and lateral dimensions of the chest.
2. The diaphragm contracts and moves downward, flattening its dome shape and increasing the vertical dimension of the thoracic cavity.
3. Thoracic volume increases, creating negative intrapleural pressure that draws air into the lungs.

This mechanical process is driven primarily by the diaphragm and external intercostal muscles.