en·do·me·tri·um / ˌendōˈmētrēəm/ • n. Anat. the mucous membrane lining the uterus, which thickens during the menstrual cycle.DERIVATIVES: en·do·me·tri·al / -trēəl/ adj.

endometrium Mucous membrane, well supplied with blood vessels, that lines the uterus. The endometrium sheds each month as part of the menstrual cycle.

endometrium The mucous membrane that lines the uterus of mammals. It comprises an upper mucus-secreting layer, which is shed during menstruation, and a basal layer, which proliferates to form the upper layer. See also menstrual cycle.

endometrium (en-doh-mee-tri-ŭm) n. the mucous membrane lining the uterus. It becomes thicker and more vascular during the latter part of the menstrual cycle and much of it breaks down and is lost in menstruation. If pregnancy becomes established the endometrium becomes the decidua.