Menstruation (aka period, monthly) is the periodic discharge of blood and mucosal tissue from the endometrium (i.e. inner lining of the uterus) through the vagina.
Is it just blood?
It's blood, as well as the surface tissue from the inner lining of her womb.
Menstrual cycle is the cycle that occurs in the uterus and ovary that makes sexual reproduction possible in fertile women. It helps to produce eggs, and prepare the uterus for pregnancy. The average menstrual cycle ranges from 21-35 days, the average being 28 days. The length of a menstrual cycle is counted in days from the first day of menstrual bleeding.
|Day||Ovarian cycle||Uterine cycle|
|1-5||Follicular phase, where through the action of rising FSH (follicle stimulating hormone) the ovarian follicles mature and get ready to release one which will dominate and mature into an egg||Menstruation, a sign that a woman has not become pregnant. Refer above|
|5-14||Proliferative phase, where estrogen causes proliferation (i.e. grow) of the endometrium (lining the uterus). As the egg matures, levels of estradiol (and estrogen) increase|
|Ovulation, where the mature egg is released from the ovarian follicles into the oviduct. Whereas estradiol suppressed luteinizing hormone (LH) production in the follicular phase, as the egg matures, levels of estradiol reach above a threshold which reverses the effect, instead stimulating LH in an LH surge, which matures the egg, and weakens the wall of the follicle. After release from the ovary, the egg is swept into the fallopian tube by the fimbria|
|14-28||Luteal phase, where FSH and LH cause remaining parts of the dominant follicle to transform into corpus luteum, which produces progesterone. Progesterone induces production of estrogen. The corpus luteum also suppresses production of FSH and LH that the corpus luteum needs to maintain itself, so the corpus luteum atrophies||Secretory phase, where the corpus luteum produces progesterone, which makes the endometrium receptive to implantation of the blastocyst and supportive of early pregnancy|
Last menstrual period (LMP) is where pregnancies are dated in weeks starting from the first day of a woman's last menstrual period. The due date can be estimated by adding 280 days (9 months and 7 days) to the LMP. This method assumes accurate recall by the mother, regular 28 day cycles, and that conception occurs on day 14 of the cycle. It may overestimate the duration of the pregnancy, and be subject to an error of more than 2 weeks. → Pregnancy U/S done in the 1st trimester should be used to determine gestational age
Is the cycle... cyclical ?
It should be. It's usually 28 days, but can be +/- 1 week, so between 21-35 days.
How does the cycle exactly occur?
So there are 2 major parts to it. Follicular and luteal phase. Follicular constitutes the 1st half of the cycle, so day 1-14, where rising FSH causes the ovarian follicles to mature. Menstruation occurs at day 1. Proliferation begins at day 5, where estrogen causes the lining of the womb to grow. Ovulation happens at day 14, at the middle of the cycle, where a mature egg is released from the ovarian follicles.
How about the luteal phase?
So it's the 2nd half of the cycle, or day 14-28. It's where the remaining parts of the dominant follicle, transform into the corpus luteum. The corpus luteum makes progesterone, which is why it's also called the secretory phase. Progesterone makes the inner lining of the womb more receptive to implantation, and supportive of pregnancy. The corpus luteum also suppresses the production of FSH and LH, that it needs to maintain itself. So, the corpus luteum itself dies.
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