Vascular endothelial growth factor and the endometrium

Endometrium in adult female primates undergoes cyclical regeneration during the menstrual cycle. A key feature of this remarkable tissue remodelling is the growth and development of the vasculature. At the end of menstruation, when two-diirds of the endometrium has been shed, the basalis contains ruptured arterioles and venules. Yet by day 5 of menstruation these vessels have been repaired and continue to undergo proliferation and branching during the rest of the cycle. Whilst intennenstrual bleeding may arise in some women, this is not usually the case, and presumably reflects the ability of endometrial vessels to maintain their integrity during the menstrual cycle. The process of new vessel growth is called angiogenesis.