Explanation

Colon is the site of water absorption from undigested and unabsorbed food (faeces). When the pallet of faeces from the sigmoid portion of colon enters into the rectum, distension of the rectal wall initiate the feeling for defecation. It is due to defecation reflex. The defecation reflex induces peristalsis movement in the sigmoid portion of the colon and rectum, which forces faecal matter towards the egestion pore