Complete the sentence by using the drop-down lists. The primary muscles of respiration are the: dropdown dropdown

Choice 1 reason: The diaphragm is the most important primary muscle of respiration. It contracts and flattens during inspiration, increasing thoracic volume and allowing air to flow into the lungs. Without diaphragm function, effective breathing cannot occur. Choice 2 reason: The intercostal muscles, particularly the external intercostals, assist in respiration by elevating the ribs during inspiration. They expand the chest cavity, supporting the diaphragm’s action. Together, these muscles are considered the primary muscles of respiration.