Defecation can be initiated by voluntary actions that stimulate a defecation reflex. This “straining” includes a large inspiration of air, followed by closure of the larynx and forceful contraction of air, abdominal muscles. As a consequence, the pressure in the abdominal cavity increases and forces feces into the rectum. Stretch of the rectum initiates a defecation reflex and external anal sphincter stimulated by increased abdominal pressure. The increased abdominal pressure also helps push feces through the rectum.