Introduction
The endometrium is a pink layer of mucous membrane that lines the inside of the uterus. The endometrium plays a particularly important role during pregnancy when the fertilized egg uses the lining of the uterus for implantation. In women who have passed puberty and are still before their menopause, the lining of the uterus is subject to hormonal influence. During this time, sex hormones influence the menstrual cycle and thus the mucous membrane. If a fertilized egg fails to implant, part of the mucosa is shed and menstruation occurs.
Function of the uterine mucosa
In general, the lining of the uterus is a protective inner layer of the uterus in all women of all ages, which lines the organ with mucous membrane cells (epithelial layer). After puberty, the mucous membrane is subject to hormonal influence and plays an important role in pregnancy. Since the lining of the uterus is necessary for the implantation of the fertilized egg, the hormonally controlled cycle of the lining is an essential part of the body’s preparation for pregnancy.
Thus, in the days following the last menstrual period, there is a change in the tissue of the mucous membrane. Through the production of certain sex hormones, the mucosa is stimulated to enlarge, a so-called proliferation takes place. After ovulation, which occurs approximately in the middle of the cycle, the so-called secretion phase of the uterine lining is initiated.
During this phase, nutrient-containing fluids are secreted by glandular cells of the mucous membrane. This is intended to create the best possible conditions for the implantation of the fertilized egg. If pregnancy fails to occur, a hormonal change causes part of the lining of the uterus to secrete nutrients and menstruation to occur.
How does the thickness of the endometrium change?
The thickness of the uterine lining varies depending on the time of the individual cycle. Since this does not occur until after puberty and is only present until menopause, the thickness of the uterine lining normally only varies in women of a mature age. The thickness of the uterine lining can be determined by means of an ultrasound examination.
This is not normally necessary, but can be carried out as part of gynaecological diagnostics in the case of certain symptoms. In pre-menopausal and post-pubertal women, an endometrial thickness of more than 14mm is indicative of a possible pregnancy. In women who are post-menopausal, a mucosa over 11mm thick may indicate the presence of endometrial cancer, which is why such findings should be clarified.
At the beginning of the cycle is the menstruation. During this a large part of the mucous membrane is shed. The thickness is therefore reduced in this phase of the cycle.
After a few days, menstruation stops and a phase follows in which the mucosa grows and becomes significantly thicker. This phase of the cycle, which lasts about 9 days, is also called the proliferation or growth phase. In the secretion phase afterwards, in which the glands that are in the mucosa secrete more fluids, the uterine lining continues to grow. The end of the cycle, if pregnancy has not occurred, is initiated by the beginning of menstruation and the repeated shedding of a large part of the mucous membrane.