The human appendix, a vestigial structure, is part of which structure.

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. It is not clear whether the appendix serves any useful purpose in humans.

The answer is anatomy.

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segmented body, an exoskeleton made from chitin, and joint appendages.