What is the role of the diaphragm in inspiration?
It contracts to pull the ribs and sternum outwards
It relaxes to decrease the volume of the thoracic cavity
It contracts to flatten and increase the volume of the thoracic cavity
It relaxes to pull the ribs outwards and sternum inwards
During inspiration, the diaphragm contracts and flattens, which increases the volume of the thoracic cavity and creates a pressure gradient for the movement of air into the lungs. Hence, option 3 is the correct answer.