The endometrium is the part of the uterus that is shed during menstruation. Answer E, rugae is a term used in anatomy to describe a series of ridges produced by the folding of the wall of an organ. Answer D, cervical mucosa deals with the lining of the cervix. While this is part of the uterus, it is not shed during menstruation.
This leaves answers B and C. Answer C, mesometrium basically is a ligament that attaches the uterus to the body. This eliminates everything except answer B, which is in fact, correct. The Myometrium is the middle layer of the uterine wall and its main job is to induce contractions for childbirth. However, when there is no fertilized egg, it is shed.
Myometrium-this question is phrased in a slightly tricky way, so it's important to break it down before looking at the answers. There are two things to think about here. First, you need to decide if a structure is part of the uterus. If it is part of the uterus, then you need to decide if it is shed during menstruation. The correct answer will be a structure that is part of the uterus but is not shed during menstruation. Answers about structures that are not shed during menstruation because they are not part of the uterine wall are incorrect. The myometrium is our correct answer. It is the middle muscular component of the uterine wall and it is not shed during menstruation. The endometrium is the inner mucosal coat of the uterus. It exhibits many characteristic changes during the menstrual cycle and all but its stratum basalis is shed during menstruation. The mesometrium is the mesentery of the uterus which forms the major part of the broad ligament of the uterus. It is not even part of the uterine wall, so it's not the answer to look for. Cervical mucosa lines the cervix, which is the inferior portion of the uterus. This mucosa is shed during menstruation. Finally, the uterus does not have rugae - rugae are the folds found in the lining of the vagina (and stomach).