Endometrium and cervix

Female reproductive organs in pelvis, with close-up of uterus, endometrium, cervix, and vagina.

The cervix is the lower part of the uterus that opens into the vagina.

The endometrium is the mucous membrane that lines the inside of the uterus. The endometrium changes throughout the menstrual cycle. About once a month, it thickens with extra blood vessels. A pregnancy can occur if a fertilized egg attaches to, or implants in, the endometrium. If a pregnancy doesn't occur, part of the endometrium is shed, causing menstrual bleeding.

Current as of: November 27, 2023

Author: Healthwise Staff
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