The intercostal muscles are a group of muscles located between the ribs. They play a crucial role in the respiratory process by helping to expand and contract the chest cavity during breathing. There are three main types: external, internal, and innermost intercostal muscles, each serving different functions in inhalation and exhalation. When you inhale, the external intercostal muscles contract, lifting the ribs and increasing the volume of the thoracic cavity. Conversely, during exhalation, the internal intercostal muscles help pull the ribs downward, aiding in the expulsion of air. Proper functioning of these muscles is essential for effective breathing.