Respiration is a process, which conducts the circulation of air between the lungs and the external environment. Two main mechanisms involved in the respiration process is the act of inspiration and expiration. Inspiration involves the inhaling of oxygen into the lungs. Expiration involves the exhalation of carbon dioxide into the external environment. Respiration is important to human body because it is a major contributor to speech. As mentioned in the paragraph above, a variety of muscles play a key role in the respiratory process. Muscles are subdivided into primary and accessory muscles. For the function of inhalation certain muscles are used. The primary muscles of inhalation (breathing in) are the diaphragm and the intercostal muscles.
