In infants, the appendix is a conical diverticulum at the apex of the cecum, but with differential growth and distention of the cecum, the appendix ultimately arises on the left and dorsally approximately 2.5 cm below the ileocecal valve. The taeniae of the colon converge at the base of the appendix, an arrangement that helps in locating this structure at operation. The appendix is fixed retrocecally in 16% of adults and is freely mobile in the remainder.
The appendix in youth is characterized by a large concentration of lymphoid follicles that appear 2 weeks after birth and number about 200 or more at age 15. Thereafter, progressive atrophy of lymphoid tissue proceeds concomitantly with fibrosis of the wall and partial or total obliteration of the lumen.
If the appendix has a physiologic function, it is probably related to the presence of lymphoid follicles. Reports of a statistical relationship between appendectomy and subsequent carcinoma of the colon and other neoplasms in humans are not supported by controlled studies.