Menstruation Cycle— (also termed as female reproductive cycle) can be defined as episodic uterine bleeding in response to cyclic hormonal changes. It is the process that allows for conception and implantation of a new life. The purpose of a menstruation cycle is to bring an ovum to maturity and renew a uterine tissue bed that will be responsible for its growth should it be fertilized. Menstruation cycle is consists of two interrelated cycles: the menstrual cycle and the ovarian cycle. Menarche—is the first menstrual period in girls, may occur as early as age 8 or 9 or as late as age 17 and still be within normal limits.
Four Phases of the Menstruation Cycle
a. Menstrual Phase (days 1–7)—shedding of the endometrium; low
estrogen levels, scanty cervical mucus; lining of the uterus is at its thinnest state; total blood loss during menses range from 30 to 80 ml and iron loss is 12 to 29 mg.
b. Proliferative phase (days 8–11)—endometrium thickens, increasing
estrogen, and cervical mucus becomes more clear, thinner, and more
elastic. This phase is also called follicular, postmenstrual and estrogenic phase. It is favorable to sperm.
c. Secretory phase (days 18–25)—Estrogen levels fall and progesterone
increases. Endometrium becomes thicker and secretes glycogen to
prepare for the fertilized ovum. If fertilization occurs, the fertilized ovum or zygote will implant in 7-8 days after fertilization.
d. Ischemic phase— (days 26–28) Levels of estrogen and progesterone fall. Spiral arteries, which nourish the endometrium, vasoconstrict causing the endometrium and blood to be shed, which begins the next menstrual phase. If fertilization does not take place, the corpus luteum shrivels as its lifespan is only up to 7 days from the date of ovulation.
Ovarian Cycle
a. Follicular phase (days 1–14)—Ovarian follicle (and ovum) mature
under the influence of FSH and LH. At first, several follicles develop,
but eventually one outgrows the others. The follicles secrete estrogen,
which accelerates maturation. Estrogen affects endometrium, and
ovulation occurs after the LH surge.
b. Luteal phase (days 15–28)—After ovulation, the ovarian follicle
becomes the corpus luteum and produces progesterone, which suppresses
the growth of other follicles. The corpus luteum degenerates
after a week or so, and, if fertilization doesn’t occur, the hormone
levels drop, the endometrium is shed, and the menstrual flow starts.
[...] Menstruation Cycle [...]