A uretha is part of a vagina.
Last time I checked, boys didnt have vaginas.
Well, maybe you do.
The lining of the uterus shed during the menstrual cycle is called the endometrium. It is the innermost layer of the uterus that thickens in preparation for potential pregnancy and is shed if fertilization does not occur.
endomoetrium
The uterus has 3 layers: Endometrium. This is the inner lining. It is shed during your period.
The lining of the uterus breaks down and is shed during menstruation if fertilization does not occur.
The lining of the uterus is shed during the menstrual phase of the menstrual cycle. This is when the body sheds the built-up uterine lining in the absence of a fertilized egg, resulting in menstrual bleeding.
During your period, the nutrient-rich lining that's been forming for almost a month is shed, if no pregnancy has occurred. This lining is need for the baby, so if your pregnant, it's not shed, and hence, no period during the pregnancy, or a time thereafter.
Premenstrually the lining thickens and is later shed if there is no fertilized egg to implant into the lining. A hormonal imbalance, infection or endometriosis can all cause a thickening of the lining, irregularly during your cycle.
Your muscles in your uterus are contracting in order to shed the lining in the uterus to rid it from your body.
The blood lining of the uterus gradually thickens during a woman's menstrual cycle in order to be prepared to receive the fertilized egg. This lining will shed during the menstrual period if no fertilized egg has implanted.
The thick uterine lining is necessary in preparation for a potential pregnancy. If fertilization does not occur, the lining is shed during menstruation. A thick lining ensures a hospitable environment for a fertilized egg to implant and grow.
If implantation does not occur, the blastocyst (embryo) does not successfully attach to the lining of the uterus. In this case, the body will shed the lining during the next menstrual period. The process starts anew during the next ovulation cycle.
The lining of the uterine cavity is called the "endometrium". It consists of the functional endometrium and the basal endometrium. Shedding of the functional endometrial lining in humans is responsible for menstrual bleeding.