To better understand diverticulitis, it helps to understand the anatomy of the intestines.
The intestine is a long, continuous, tube inside the body. It lets the body absorb nutrients from food and liquids. The intestine is about 22 feet long. It includes the large intestine (colon) and the small intestine.
The small intestine has three parts:
- Connects to the stomach
- Middle portion of the small intestine
- Lower portion of the small intestine that connects to the cecum (first part of the large intestine)
The large intestine is also known as the colon. It is the last portion of the intestine.
The colon has several parts, including:
- The portion of the colon that connects to the ileum (small intestine). The appendix is a finger-like pouch that comes off of the cecum.
- Ascending colon:
- The first section after the small intestine, located on the right side
- Transverse colon:
- Sits horizontally across the upper abdomen
- Descending colon:
- Located on the left side of the abdomen
- A short, S-shaped section above the rectum
- The lowest internal part of the colon
- Hall NR. Managing diverticular disease. Practitioner. 2003 May;247(1646):392-6, 400, 402 passim. 
- Janes S, Meagher A, Frizelle FA. Elective surgery after acute diverticulitis. Br J Surg. 2005 Feb;92(2):133-42. 
- Pugliese R, Di Lernia S, Sansonna F, Scandroglio I, Maggioni D, Ferrari C, Costanzi A, Chiara O. Laparoscopic treatment of sigmoid diverticulitis: a retrospective review of 103 cases. Surg Endosc. 2004 Sep;18(9):1344-8. 
- Simpson J, Spiller R. Colonic diverticular disease. Clin Evid. 2004 Dec;(12):599-609.