Final answer:
The scalene muscles help to increase the size of the thoracic cavity during inhalation, which allows air to enter the lungs due to a decrease in internal pressure.
Step-by-step explanation:
The scalene muscles help to increase the dimensions of the thoracic cavity. During inhalation, these muscles, along with the diaphragm and intercostal muscles, contract to expand the thoracic cavity, which in turn decreases the pressure inside the lungs compared to the atmospheric pressure. The scalene muscles help to increase the thoracic cavity dimensions. These muscles work together to flex, laterally flex, and rotate the head, and also contribute to deep inhalation. When you inhale, your chest rises because the thoracic cavity expands, and when you exhale, your chest falls because the thoracic cavity decreases in size.This pressure differential allows air to flow into the lungs, facilitating the process of deep inhalation.