Allergic to Milk Anatomy
To better understand lactose intolerance, it helps to understand the anatomy of the intestines.
The intestine absorbs nutrients from food and liquids. The intestine is about 22 feet long in an adult. It includes the large intestine 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
- Lovelace HY, Barr SI. Diagnosis, symptoms, and calcium intakes of individuals with self-reported lactose intolerance. J Am Coll Nutr. 2005 Feb;24(1):51-7. 
- Suarez FL, Savaiano DA, Levitt MD. Review article: the treatment of lactose intolerance. Aliment Pharmacol Ther. 1995 Dec;9(6):589-97. 
- Swagerty DL Jr, Walling AD, Klein RM. Lactose intolerance. Am Fam Physician. 2002 May 1;65(9):1845-50.