Cecum and appendix
The ileum joins the large intestine from the side, through the ileocecal valve. Below the junction the cecum forms a blind pouch about 6 cm deep in the lower right abdomen. The valve and a thickened ring of muscle let chyme pass into the colon and keep the colon's contents, rich in bacteria, from flowing back.
The cecum opened, showing the opening of the ileum with its valve and the opening of the appendix, Gray's Anatomy, 1918, figure 1075Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray1075.png)
The appendix opens from the cecum about 2 cm below the valve. It is a narrow tube, on average about 9 cm long, with much lymphoid tissue in its wall.
The appendix cut across, with lymph nodules in its wall, Gray's Anatomy, 1918, figure 1074Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray1074.png)
When its opening is blocked it can swell and become infected. The pain of appendicitis often starts around the navel and moves to the lower right. Some 7 to 9 percent of people have it in their lifetime.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on the large intestine.
- Arthur Guyton and John Hall, Textbook of Medical Physiology, 13th ed. (2016), ch. 64.
- Dennis Addiss and others, The epidemiology of appendicitis and appendectomy in the United States, American Journal of Epidemiology 132 (1990): 910 to 925.
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