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The endometrium is the mucous membrane that lines the inside of the uterus (womb).
The endometrium changes throughout the menstrual cycle. It becomes thick and rich with blood vessels to prepare for pregnancy. If the woman does not get pregnant, part of the endometrium is shed, causing menstrual bleeding.
Last Revised: March 20, 2013
Author: Healthwise Staff
Medical Review: Sarah Marshall, MD - Family Medicine & Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology
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