endometrium /en′dōmē″trē·əm/ [Gk, endon + metra, womb] , the mucous membrane lining of the uterus, consisting of the stratum compactum, the stratum spongiosum, and the stratum basale. The endometrium changes in thickness and structure with the menstrual cycle. The stratum compactum and the stratum spongiosum constitute the pars functionalis and are shed with each menstrual flow. The pars functionalis is known as the decidua during pregnancy, when it underlies the placenta. Compare myometrium, parametrium.
