Saturday, January 15, 2011

Facts on Menstrual cycle

When I was still a student, I didn’t like maternal and child nursing or topics that pertain to taking care of pregnant women and the child. I really find it hard to understand and memorize facts about it and so I really am having difficulty appreciating it. But then again, when you are in this profession or whatever profession you are in right now you really could not get away from topics that you hated most back when you were studying. And so, I would like to take this opportunity to share to you some information’s from Maternal and child nursing which I think is very helpful not only for me but also for all of the students out there who are finding their way to becoming a nurse. Lets start from some basic concepts.

Menstrual Cycle Physiology

What is the average duration of the                              The average duration of the
menstrual cycle, duration of menses, and                  menstrual cycle is 28 days. The
amount of blood loss during menses?                         average duration of menstrual flow
is 4 days. On an average, women lose
less than 60 mL of blood during each

What are the two phases of the menstrual                 Follicular (or proliferative) phase and
cycle and how long does each last?                             the luteal (or secretory) phase,
separated by ovulation. (Follicular/
luteal describe the ovarian changes,
proliferative/secretory describe the
endometrial changes)
By convention, day 1 marks the onset
of menses. The follicular phase begins
on day 1 and lasts approximately
14 days (days 114) in a 28-day cycle,
until ovulation occurs. The luteal
phase then commences and lasts until
approximately day 28 (days 1428)

What causes the variability in the length                     The duration of the follicular phase
of the menstrual cycle?                                                    (the luteal phase is constant)

Describe the hormone pathway involved                    The cycle begins in the arcuate
in the menstrual cycle (see Fig. 4-1) and                     nucleus of the hypothalamus where
name which structures produce                                   gonadotrophin-releasing hormone
each hormone                                                                     (GnRH) is released in a pulsatile
fashion. GnRH stilmulates the
anterior pituitary to release folliclestimulating
hormone (FSH) and
luteinizing hormone (LH). These
gonadotropins then cause the ovaries
to release the sex steroid hormones
estradiol and progesterone.
Estrogenand progesterone feedback
negatively on both the hypothalamus
andthe pituitary gland

What is happening in the ovary during the                     The ovary beings with
menstrual cycle?                                                               approximately one million primordial
follicles at birth (20 million at week
20 in utero). Each follicle contains an
oocyte arrested in prophase of
meiosis. The oocyte is surrounded by
pre-granulosa cells and these are
surrounded by pre-theca cells. In the
follicular phase, FSH stimulates the
pre-granulosa cells to become
granulosa cells. The granulosa cells
secrete estradiol. The pre-theca cells
in turn become theca cells and secrete
androgens, which are aromatized by
the granulosa cells into estradiol.
One follicle with the highest number
of granulosa cells, FSH receptors, and
estradiol production becomes the
dominant follicle and all other
follicles become atretic. This follicle is
released during ovulation and
becomes the corpus luteum. The
corpus luteum secretes progesterone
and a smaller amount of estrogen
during the follicular phase of the
cycle. If fertilization does not occur, it
degenerates into the corpus albicans

What is the function of the corpus luteum?                Secretion of progesterone and
estradiol. It is the only structure that
produces progesterone in significant
quantities which sustains the
pregnancy until the placenta is

What is happening to hormone levels in                      At menstruation, concentrations of
the follicular phase?                                                          estradiol, progesterone, and LH are
at their lowest point. FSH and LH
levels begin to rise in response to
the low estrogen and progesterone.
Estradiol levels, secreted from the
dominant ovarian follicle, begin to
rise by day 4. Just before ovulation,
estradiol levels peak. This peak
causes a positive feedback on LH
secretion, leading to the LH surge
and a smaller FSH surge, which
results in ovulation 3038 hours
later. Progesterone levels remain low
throughout the follicular phase
What is happening to hormone levels in                      The LH surge causes granulosa and
the luteal phase?                                                                theca cells to secrete progesterone
and smaller amounts of estrogen.
Progesterone peaks 34 days after
Estrogen levels decrease immediately
after ovulation but slowly rise with
the growth of the corpus luteum.
Progesterone and estrogen (at low to
moderate levels) both act via negative
feedback to suppress LH and FSH. If
fertilization and implantation do not
occur, progesterone and estradiol
levels diminish after 11 days. FSH
increases as the corpus luteum

What is happening to the endometrium in                   At menses, the endometrium sloughs
the proliferative phase?                                                   off until it becomes a thin line. During
the proliferative phase estradiol levels
rise, resulting in the proliferation of
the uterine endometrium. The
endometrium becomes thicker and
more glandular and the spiral arteries
elongate. On ultrasound, it appears as
a triple stripe pattern

What is happening to the endometrium in                   The progesterone released from the
the secretory phase?                                                        corpus luteum leads to slowing of
endometrial proliferation,
reorganization of the glands (resulting
in a more edematous stroma), and
further coiling of the spiral arteries.
This results in the loss of the triple
stripe pattern and its replacement
with a uniformly bright
endometrium. If pregnancy does not
occur, the endometrium degenerates

What are the primary clinical                                          Estradiol
manifestations of estradiol and                                     Endometrium: thickens stroma and
progesterone during the menstrual cycle? elongates glands (creates proliferative
endometrium); Endocervix: stimulates
secretion of thin, watery mucus.
Produces ferning pattern when
spread on a glass slide;
Vagina: promotes vaginal thickening
Endometrium: causes tissue to
become edematous and blood vessels
to thicken and twist (creates
secretory endometrium);
Endocervix: thickens endocervical
mucus, causing it to become stringy;
Breast: stimulates acinar glands,
causing breasts to round;
Other: raises basal body temperature
by 0.61°F. Causes some women to
have the emotional, physical, and
behavioral changes of premenstrual
syndrome (PMS)

What layer of the endometrium sloughs                      The functionalis layer (inner layer)
off during menses?                                                           sloughs off after glandular and
stromal degeneration

What hormone mediates menstrual                             Prostaglandins, especially PGF2á. It is
cramps and how is it synthesized?                               released by the secretory
endometrium in response to
progesterone and causes uterine

Thats it. Hope you learned something from this. Next time, I will be posting about family planning.. till next time..


  1. very useful knowledge,. hank for your information

  2. very informative article, these are things every women should know.

  3. is ur diagram copyright? i want to use it for an essay?

  4. so helpful thanks! med student...i keep learning this and forgetting it over and over again, u broke it down very bookmarking this page


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