ABSTRACT
The basis for all understanding of endometrial biology is to realize that this tissue is composed of different cell types. The major cell types in the endometrium are epithelial cells, stromal cells and vascular endothelial cells. Epithelial cells in glands and the luminal epithelium are functionally quite different, and even within the same anatomical position epithelial cells may have different functions. Endometrial stroma is composed of a heterogeneous population of cells, the fibroblast-like cells being the major cell type. In addition, endometrial stroma contains various types of leukocytes, the number of which varies depending on the phase of the menstrual cycle. Some of the fibroblast-like stromal cells undergo decidual differentiation during the late luteal phase. Also, the extracellular matrix that underlies the epithelium as the basement membrane and surrounds the stromal cells as interstitial matrix is assumed to play an important role in endometrial biology.
