The primate uterus: Cyclic changes

Herein we describe the events involved in hormonal regulation of the primate uterus. At the onset of each menstrual cycle the luminal portion of the uterine lining, the endometrium, is sloughed during menstruation and then regenerated in the follicular phase of the cycle. In the luteal phase, the endometrium is transformed into four distinct zones characterized by the degree of glandular sacculation, steroid receptor expression, cell proliferation, and vascularization. Progesterone drives endometrial secretory differentiation. In the absence of embryo implantation, the decline in progesterone at the end of the cycle leads to menstruation and the start of a new cycle.