MENSTRUAL CYCLE

INTRODUCTION
• Menstrual cycle is the cyclic events that takes place in a rhythmic fashion during the
reproductive period of a woman’s life.
• Onset of menstrual cycle- generally 12-15 years
• First ever occurrence – Menarche
• Cessation – menopause
• Duration – 28 days
 PHASES IN MENSTRUAL CYCLE
❑ PROLIFERATIVE PHASE
❑ SECRETORY PHASE
❑ PREMENSTRUAL PHASE
❑ MENSTRUAL PHASE
 PROLIFERATIVE PHASE
• The layer of endometrial tissue lost in the last menstruation is rebuilt during this
phase (Statum functionalis).
• By the end of menstruation ( around day 5), endometrium is about 0.5mm thick and
consist only of stratum basalis.
• As new follicles develops, they secrete more estrogen.
• Estrogen stimulates mitosis in the stratum basalis and helps in regrowth of blood
vessels.
• By day 14, endometrium become 2-3 mm thick.
 SECRETORY PHASE
• This phase extends from day 15 to day 26 of a typical
cycle.
• After ovulation, corpus luteum secretes progesterone.
• Progesterone stimulate endometrial glands to secrete
glycogen.
• By the end of this phase, endometrium becomes
5-6mm thick.
 PREMENSTRUAL PHASE( ISCHEMIC PHASE)
• It occurs during the last 2 days, it is also the period of endometrial
degeneration.
• As there is no pregnancy, corpus luteum atrophies and progesterone
level falls.
• Drop in progesterone triggers contraction of spiral arteries of
endometrium, thereby causing endometrial ischemia.
• As a result endometrium falls from uterine wall and get mixed with
blood and serous fluid in lumen and forms menstrual fluid.
 MENSTRUAL PHASE
• When enough menstrual fluid accumulates in uterus, it begins
to discharge from vagina for a period called ,Menstrual phase.
• First day of discharge marks day 1 of a new cycle.
• On an average woman expel 40ml of blood and 35ml of serous
fluid over a 5 day period.
• Menstrual fluid contains fibrinolysin, so it does not get clot.
 CHANGES DURING MENSTRUAL CYCLE
❑ OVARIAN CHANGES

❑ UTERINE CHANGES

❑ VAGINAL CHANGES

❑ CHANGES IN CERVIX
 OVARIAN CHANGES
❑ FOLLICULAR PHASE

❑ OVULATION

❑ LUTEAL PHASE
 FOLLICULAR PHASE
• Usually extends from the beginning of menstruation until the time of ovulation
which takes place on 14th day.
• The portion from the end of menstruation until ovulation is called preovulatory
phase.
• After ovulation, a new cohort of follicles descends from the cortex, deeper into the
ovary and begins to grow.
• Each follicle develops an antrum.
• There occur a 5- day selection window in which one of them is selected to mature
and ovulate in the next month.
• This follicle is called Dominant follicle.
• During this phase FSH stimulates the continued growth of all follicle.
• It also stimulate granulosa cells of antral follicles to secrete estradiol.
• In response to estradiol, dominant follicle upregulates its receptors for FSH, LH and
estradiol itself and become sensitive to hormone.
• Anterior pituitary gland secrete less FSH, but an increasing amount of LH.
• The dominant follicle has the richest blood supply and greatest density of FSH
receptors, so it continues to grow( reaches a diameter of about 20mm) by the late
follicular phase
• It is then regarded as the graafian( mature) follicle.
 OVULATION
• It is the rupture of mature follicles and the release of its egg ( around day 14).
• Estradiol stimulates a surge of LH and a lesser spike in FSH secretion by the
pituitary.
• Follicular fluids are build rapidly and the follicles swell( twice the usual thickness of
ovary) and looks like blister on the ovarian surface.
• The follicular wall and adjacent ovarian tissues are weakened by inflammation and
proteolytic enzymes.
• With mounting internal pressure and weakenening of walls, the mature follicle
ruptures.
• Ovulation takes only 2-3 minutes.
• A nipplelike stigma appears on the ovarian surface over the follicle and it seeps
follicular fluid for 1-2 minutes and the follicle bursts.
• The remaining fluid oozes out and are swept up by ciliary current and taken into
uterine tube.
 LUTEAL PHASE
• From day 15 – 28.
• During this phase corpus luteum is developed and hence this phase is called luteal
phase.
• After ovum is released, the follicle is filled with blood which is called corpus
haemorrhagicum and are called lutein cells.
• This transformation from ruptured follicle to corpus luteum is regulated by LH.
• LH stimulate growth of corpus luteum and also increases the levels of estradiol and
progesterone.
• LH secretion declines steadily over the rest of the cycle, as does FSH.
• This decline is because of the high levels of estradiol and progesterone.
• If pregnancy does not occur, the corpus luteum undergo involution around day 22.
• And by day 26 involution completes and now corpus luteum becomes an inactive bit
of scar tissue called corpus albicans.
 UTERINE CHANGES
❑ PROLIFERATIVE PHASE
❑ SECRETORY PHASE
❑ MENSTRUAL PHASE
 HORMONAL REGULATION
❑ FOLLICLE STIMULATING HORMONE( FSH)
❑ LUTEINIZING HORMONE( LH)
❑ ESTROGEN
❑ PROGESTERONE
❑ FSH – Stimulates egg development and release of estrogen
❑ LH – Stimulate the release of egg and stimulate estrogen and progesterone
production
❑ Estrogen – Promote development and maintenance of female reproductive
structures, feminine secondary sex characters
• Inhibit release of GnRH, FSH, LH
❑ Progesterone – Works with estrogen to prepare endometrium for
implantation
• Prepare mammary glands to secrete milk
• Inhibit release of GnRH and LH
 ANDROGEN IN WOMEN
• Androgens like testosterone are sex hormones.
• Androgen help people enter puberty and mature physically
• All genders make androgens, but males produce more of them.
 ROLE OF ANDROGENS IN WOMEN
• Regulates menstruation
• Aids conception and pregnancy
• Minimizes bone loss( osteoporosis)
• Stimulate pubic and underarm hair growth
COMMON ANDROGEN RELATED HEALTH PROBLEMS
• Hyperandrogenism is seen in females and that can cause Polycystic Cystic Ovarian
Syndrome( PCOS).
• Hypoandrogenism can lead to;
Bone fractures and osteoporosis
Fatigue
Low sex drive
 ANDROGEN CONDITIONS THAT AFFECT FEMALE
• Acne
• Amenorrhea or abnormal menstruation
• Excessive hair growth( hirsutism) or hair loss
• High blood pressure and high cholesterol
• Infertility
• Obesity
• Ovarian tumors
 REFERENCE
• ANATOMY AND PHYSIOLOGY THE UNITY OF FORM AND
FUNCTION,KENNETH S. SALADIN, McGraw- Hill education.

• GYTON AND HALL TEXTBOOK OF MEDICAL PHYSIOLOGY, JOHN