caecum cecum A pouch in the digestive tract that connects the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve, and is the beginning of the large intestine. It is also separated from the colon by the cecocolic junction. intestinum crassum caecum blind intestine intestinum crassum cecum caecum ceca caeca blindgut intestinum caecum digestive tract diverticulum