pouch that is considered to be the beginning of the large intestine

The cecum is a part of the large intestine. It helps with fermenting dietary fiber. It comes before the colon and after the ileum in the gastrointestinal system. The appendix is connected to the cecum. The size of the cecum varies in humans and other omnivores but it is large in herbivores and small in most carnivores.

Drawing of colon seen from front
(cecum colored red)