Abdominal Pregnancy Anatomy
To better understand ectopic pregnancy, it helps to understand the anatomy of the uterus, cervix, and Fallopian tubes.
The female reproductive organs include the vagina, cervix, uterus, fallopian tubes and ovaries. The lining of the uterus is called the endometrium.
Before ovulation, the endometrium grows and becomes thick: the endometrial tissue and blood vessels support the fertilized egg when it enters the uterus.
During ovulation, an egg is released from one of the ovaries and enters the fallopian tube. If the egg is fertilized as it passes through the fallopian tube, it attaches to the endometrium on the inside of the uterus. The endometrium continues to support the fertilized egg as it grows.
If the egg is not fertilized, the egg does not attach to the endometrium and the endometrium breaks down. The uterus sheds the endometrium, which causes the bleeding associated with the menstrual period.
Female reproductive anatomy:
- Aboud E. A five-year review of ectopic pregnancy. Clin Exp Obstet Gynecol. 1997;24(3):127-9. 
- Dialani V, Levine D. Ectopic pregnancy: a review. Ultrasound Q. 2004 Sep;20(3):105-17. 
- Fisch JD, Ortiz BH, Tazuke SI, Chitkara U, Giudice LC. Medical management of interstitial ectopic pregnancy: a case report and literature review. Hum Reprod. 1998 Jul;13(7):1981-6. 
- Furlong LA. Ectopic pregnancy risk when contraception fails. A review. J Reprod Med. 2002 Nov;47(11):881-5. 
- Lozeau AM, Potter B. Diagnosis and management of ectopic pregnancy. Am Fam Physician. 2005 Nov 1;72(9):1707-14.