Which muscles are classified as accessory muscles of respiration?

The classification of accessory muscles of respiration includes those muscles that assist in the process of breathing, particularly during times of increased respiratory effort or distress. The neck muscles (such as the sternocleidomastoid and scalene muscles) play a significant role in elevating the thorax and increasing lung volume, especially when the primary muscles like the diaphragm are insufficient to meet the body's respiratory demands. The abdominal muscles can also contribute by aiding forced expiration, thereby helping to push the diaphragm back up and expel air more efficiently.

Understanding the function of accessory muscles is crucial in clinical situations where respiratory distress is present, as their engagement indicates a need for increased ventilatory support. The primary muscles, such as the diaphragm and intercostals, perform normal breathing functions, while accessory muscles come into play during exertion or respiratory compromise.