Breathing is the act or process of respiration and it consists of two phases, inspiration and expiration. During inspiration, the diaphragm and the intercostals muscles contract. the diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the intercostals muscles pull up the ribs to expand the rib cage and further increasing the volume of the alveoli (Blake, 2001). The increase of volume in the alveoli lowers the air pressure below the atmospheric pressure. As we all know that air always flows from a region of high pressure to a region of lower pressure. …
