Appendix. Light micrograph of a section through a human appendix. The appendix is a blind-ending small diameter tubular extension of the gut, arising from the caecum of the large bowel. Seen here are the lining mucosa around a small central lumen (space, white), and several blue-stained tissue patches that represent lymphoid follicles. Magnification: x11, when printed 10 centimetres high.