The appendix is a narrow, worm-like structure, hence the term "vermiform," meaning "worm-shaped." It is typically 5-10 cm in length and 0.5-1 cm in diameter, though lengths of up to 20 cm have been observed. Appendix, in anatomy, a vestigial hollow tube that is closed at one end and is attached at the other end to the cecum, a pouchlike beginning of the large intestine into which the small intestine empties its contents. The meaning of appendix . Definition of appendix . English dictionary and integrated thesaurus for learners, writers, teachers, and students with advanced, intermediate, and beginner levels. The appendix is a narrow blind-ended tube that is attached to the posteromedial end of the cecum (large intestine). It contains a large amount of lymphoid tissue but is not thought to have any vital functions in the human body. In this article, we shall look at the anatomy of the appendix – its anatomical structure and relations, neurovascular supply and lymphatic drainage.