What does the endometrium line?

The endometrium is the inner lining of the uterus. It plays a crucial role in the reproductive system by providing a suitable environment for implantation of a fertilized egg and supporting early stages of pregnancy. The endometrium thickens and sheds during the menstrual cycle, which is a key feature of female reproductive health. The other structures listed do not have this lining; for instance, the ovary produces eggs but is not lined by endometrial tissue, the fallopian tube is primarily a site for fertilization and transport of the egg, and the vagina serves as the passageway to the external environment and does not have an endometrial lining. Understanding this distinction is important when studying reproductive anatomy and physiology.