ABSTRACT
The primary functions of the human endometrium are to allow the implantation of a normal embryo and provide mechanisms for the clearance of tissue and hemostasis at menstruation. At the same time, the endometrium must also provide a defense against invasion by potential pathogens and prevent the implantation of an abnormal embryo. In order to achieve these functions, the endometrium undergoes profound changes in structure and function during each cycle that result in defined periods of proliferation, embryo receptivity, and menstruation. The cyclic structural changes are evident on every level of examination, from gross inspection to electron microscopy. Both structural and functional changes are the result of changes in the molecular components of each cell, whereas a lack of appropriate cyclic changes is thought to underlie many common disorders, including abnormal uterine bleeding, infertility, endometriosis, and endometrial cancer. Therefore, a thorough understanding of the molecular and cellular alterations of the endometrium across the cycle should provide new approaches to the prevention, diagnosis, and treatment of endometrial disorders.
