The expression of many of these proteins vary depending on the menstrual cycle, for example the progestorone receptor and thyrotropin-releasing hormone both expressed in the proliferative phase, and PAEP expressed in the secretory phase.Other proteins such as the HOX11 protein that is required for female fertility, is expressed in endometrial stroma cells throughout the menstrual cycle.In humans, the cycle of building and shedding the endometrial lining lasts an average of 28 days.The endometrium develops at different rates in different mammals.In both cases, the endometrium initially proliferates under the influence of estrogen.However, once ovulation occurs, in addition to estrogen, the ovary will also start to produce progesterone.These two layers occur only in endometrium lining the cavity of the uterus, not in the lining of the uterine (Fallopian) tubes: In the absence of progesterone, the arteries supplying blood to the functional layer constrict, so that cells in that layer become ischaemic and die, leading to menstruation.
The endometrial lining undergoes cyclic regeneration. Humans and great apes display the menstrual cycle, whereas most other mammals are subject to an estrous cycle.
The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus.
It has a basal layer and a functional layer; the functional layer thickens and then is sloughed during the menstrual cycle or estrous cycle.
The entire process occurs over a period of several days.
Menstruation may be accompanied by a series of uterine contractions; these help expel the menstrual endometrium.
The endometrium consists of a single layer of columnar epithelium plus the stroma on which it rests.