Kindly pay attension to key words as you read….
Reproductive cycle begins at puberty as the hypothalamus ( rgan within the brain) pulse Generator is activated.
Menstrual cycle are mostly irregular during the first 2yrs after first menses (Menachre) and 3yrs before cessation of menses( menopause)
Secretion from the brain( Gonadotrophin releasing Hormone (GnRH) guides secretion of Follicle stimulating hormone (FSH) and leutinizing hormone (LH)
The following hormone play vital role in maintaining regular mense/ fertility namely estrogen,progesterone norepinephrine, dopamine B- endorphin ,inhibit, Activin
GnRH must be released in pulsatile fashion( pulse like fashion)usually once between 60-90 minutes
Variation in pulse frequency of GnRH release alters the ration of FSH to LH. Increase frequency of GnRH like once in one hour is common in follicilar ( egg) development phase of menstrual cycle and result in follicular recruitment. While release of once in 2-3 hr is typical of luteal phase( second phase of menstrual cycle)
Menstrual cycle can be divided for convenience into 4 phases namely menstrual phase. .During the menses,follicular phase when follicle(eggs) are recruited ;ovulation phase..period surrounding ovulation and luteal phase ..from ovulation to onset of next mense.
Follicle(eggs) do not developed when the LH pulse decline to interval of less than 2-3 hrs. Also high and prolong GnRH exposure saturated GnRH receptors causing anovulation (no release of egg on that cycle) by down regulation.
Follicles are usually stored in a “resting pool”. Once they leave the resting state there is only two possibilities.. ovulation or altresia (dying off).Altresia account for more than 99% of follicular lost.
It takes average of 85 days ( about 3 completed menstrual cycle)for follicle to reach point of ovulation from the “resting pool”
Process of follicle (egg) generation ie folliculogenesis can be divided into 4 phases..namely recruitment selection, Dominance and ovulation phases.
Recruitment takes place between day 2,3 and 4 of mense (while you are menstruating) and by day 5,both menstrual flow( in most women) and follicular recruitment ends. In some women, this recruitment process is defective and contributes to infertility in some women
Dominant phase…Naturally except ovulation is induced( assisted)spontaneously multiple ovulation is atypical (rare) .The dorminant ( selected)follicle is selected early when it developed LH receptors while other follicles that started the journey dies off.
Selection..Usually Day 7 Mark’s the time when the influence of a single follicle creates an environment in which only it can adequately mature and be ovulated.
By Day 8,Selection end and maturation begins in preparation of ovulation.
While these are going on at the ovarian end, the Uterine lining that started 1cm will grow to a thickness of 8-10mm and by day 11,thickness will reach 16–20mm.while estradiol level( esttogen) reaches its peak of 24-36hrs before ovulation
When ovulation approaches around day 14 in a 28day menstrual cycle, blood supply to the ovary increase,the ovarian ligament contract, pulling the ovary closer to the fallopian tube ,so that when ovulated, it can enter the tube for transportation. .
Ovulation occurs 10-12hour of LH peak and 36 hours after the estradiol peak.The most reliable indicator for the timing of ovulation is the onset of the LH surge which begins 28-32 hrs before ovulation.
A defective luteal phase can contribute to infertility and early pregnancy wastage .This defect is becoming more common lately among women and greatly contributing to menstrual irregularity and infertility
After 2-3 days of tubal transport following sucessgul fertilization , the embryo enters the Uterine cavity on day 17 and will not be attached to the uterine epithelium( lining for2-3 days. The embryo is highly susceptible to injurious condition at this phase as other phase too
Implantation takes place between day 20-24 in a 28 day cycle.. Peak level of progesterone are seen between 8-9days after ovulation that corresponds to time of implantation of the fertilised embryo.
Human Chorionic Gonadotrophins (HCG)..Basis for pregnancy test is secreted from day 22 following invasion of the endometrium and HCG serves to rescue the corpus luteum and maintain function with secretion of progesterone until placenta ( tissue that is delivered after baby is delivered) start producing hormones to keep the pregnancy going..
Without fertilization and subsequent implantation,decreasing hormonal (steroidal) level leads to increasing coiling and vasoconstriction of the spiral arteries which supply the upper 2/3rd of the functional endometrium and fibrin thrombus accumulation within endometrial capillaries
Mense therefore ensures at day 28. Menstrual bleeding is controlled by the vasoconstriction of the ruptured basal arteries in the denuded basal layer. Defects in these area and clothing factors deficiency can result in heavy menstrual losses.
The basal layer is not shed and it is the from this layer that the uterus regenerates again and the cycle resumes back .
Clinical implication…All issue that relates to irregular menses, not ovulating in a menstrual cycle, infertility, prolong bleeding ,heavy flow and pregnancy wastages ( miscarriges) ,all have connection to improper functioning of the menstrual cycle and also form bases of treatments including infertility treatment
If you need further information and evaluation contact us on our various social handles facebook page: GCEM hospital,or visit wwwgcemhospital.com or follow me on Facebook Blessing Okangba; Instagram drokangba, Twitter drOkangbaBC .
I appreciate Vivian Lewis MD ; Landes Bioscience Vademecum
Dr Okangba Blessing
Consultant Obs//Gynae. GCEM Hospital