What Are the Functions of the Human Appendix?

Following Darwin's theory of evolution, scientists considered the appendix a leftover vestigial organ, meaning an organ previously more fully developed in the human species that currently serves no function. Studies prove otherwise. Appendix function warrants further research, but strong evidence substantiates this 80-million-year-old body part's role in health and development.

Features

• A finger size, slimy, dead-end sac, the appendix measures between 2 and 8 inches long and a half-inch wide. According to Talkorigins.com, "The appendix is longest in childhood and gradually shrinks throughout adult life. The wall of the appendix is composed of all layers typical of the intestine, but it is thickened and contains a concentration of lymphoid tissue."

Fetal Development

• The appendix assists in fetal development. According to Christopher Wanjek on Livescience.com, "As quickly as 11 weeks after conception, the appendix starts making endocrine cells for the developing fetus. Endocrine cells secrete useful chemicals, such as hormones, and the appendix endocrine cells secrete amines and peptide hormones that help with biological checks and balances as the fetus grow."

Immune Function

• The appendix helps create and train white blood cells. Acting as a lymphoid organ after birth, the appendix wards against disease. According to LiveScience.com, "Lymphoid organs, with their lymphoid tissue, make white blood cells and antibodies. The appendix, by virtue of its lymphoid tissue, is part of a complicated chain that makes B lymphocytes (one variety of white blood cell) and a class of antibodies known as immunoglobulin A antibodies." The location of the appendix exposes white blood cells to a bounty of drugs, viruses and bacteria that cells learn how to fight. Chemicals also originate in the appendix that dispatch white cells to needed locations throughout the body.

Biofilms

• According to Medical News Today, "Different microbes that help the digestive system break down foods inhabit the gut. The gut rewards these microbes by feeding them and keeping them safe." William Parker, research immunologist for Duke University Medical Center, and his team looked at the relationship between the bacteria and found what is called a biofilm. Medical News Today explains it is "a thin and delicate layer of microbes, mucous and immune system molecules living together on the lining of the gut." The scientists say the immune system looks after these microbe colonies in the biofim. Parker states, "By protecting these good microbes, the harmful microbes have no place to locate. We have also shown that biofilms are most pronounced in the appendix and their prevalence decreases moving away from it."

Safe House

• Immunologist William Parker explains in the Journal of Theoretical Biology, that the appendix protects important bacteria. Parker's report states,"the human appendix is well suited as a ''safe house'' for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen." (See Reference 4) In the event of illnesses causing diarrhea, the appendix harbors good bacteria until the system cleanses the body completely. Uncontaminated, the bacteria leave the appendix, rebooting the digestive system and repopulating the gut.