1. The menstrual cycle
Dr Ismaiel Abu Mahfouz

2. Menstruation Definition
A woman's monthly bleeding from the reproductive
tract induced by hormonal changes of menstrual
cycle
For menstruation to occur
Coordinated HPO axis
Responsive endometrium
Patent outflow

3. The menstrual cycle hormones

4. GnRH A peptide hormone Synthesized and released from GnRH neurons in
hypothalamus
Responsible for the release of FSH & LH from
 anterior pituitary

5. FSH A glycoprotein polypeptide hormone
Granulosa cell proliferation and differentiation
Antral follicle development
Oestrogen production
Inhibin synthesis
Induction of LH receptors on dominant follicle

6. LH A glycoprotein hormone The main promoter of constant androgen
production from the theca cell
The pre-ovulatory LH surge
Triggers ovulation and follicular rupture
Induces resumption of oocyte meiotic maturation
Causes luteinization of granulosa cells (formation of corpus luteum)

7. Estradiol
Suppresses FSH due to a -ve feedback leading to selection of a dominant follicle
Triggers LH surge due to a +ve feedback
Increases endometrial thickness
Stimulates cervical glands to secrete a particular type of mucus which is essential for sperms to pass through

8. Progesterone
Induces secretory endometrium to enhance embryo implantation
Maintains endometrium in 1st week of pregnancy
Modifies endometrial glandular structure (more number, more tortuous)
Involved in gene expression in endometrium needed for implantation

9. Inhibin Secreted by granulosa cells in ovary
Two hormones : Inhibin A & B
Secreted by granulosa cells in ovary
Inhibits production of FSH via –ve feedback
Involved in control of gamete production,
embryonic and fetal development

10. Hormonal interaction GnRH Sex steroids Gonadotropins - FSH - LH
- Esradiol
- Progesterone
Gonadotropins
- FSH
- LH

11. The ovarian cycle The endometrial cycle
The menstrual cycle
The ovarian cycle
The endometrial cycle

12. The ovarian cycle

13. The Ovarian Cycle Follicular phase (pre-ovulatory)
Recruitment & selection of dominant follicle
Increasing levels of estradiol & inhibin B
Ovulatory phase
LH surge
Rupture of pre-ovulatory follicle wall
Release of viable ovum
Luteal phase (post-ovulatory)
Corpus luteum development
Increasing levels of progesterone
Secretory changes in endometrium
Menstrual phase

14. Follicular Phase
A group of the most mature follicles (called “antral follicles”) are recruited
Only follicles most sensitive to FSH undergoes a further development
Follicle most sensitive to FSH continue to
develop and produce a large amount of estradiol
and inhibin B
Remaining follicles become atretic (99%)

15. Ovulatory phase An event in the menstrual cycle by which a
selected mature follicle breaks and releases a
viable oocyte
Each month, one egg is released ; occasionally, two or more
If pregnancy does not occur, menstruation
starts after exactly two weeks

16. Ovulatory phase Mechanism of follicle rupture
Increase of intra-follicular pressure
Perifollicular ovarian smooth muscle contractions
Vascular alterations in peri-follicular vessels
Prostaglandins and proteolytic enzymes
Cytokines, O2 free-radicals, nitric oxide and angiotensin II

17. Ovulatory phase Ovulation
Ovulation occurs hours after onset of LH surge

18. Luteal phase Peak level of progesterone occurs 7 days after ovulation
This approximates the time of implantation
In early pregnancy, hCG maintains luteal function with secretion of progesterone until placental steroidogenesis is established

19. Menstrual phase
Rapid ↓ in steroids → shedding of the unused endometrium
Inflammatory mediators (PGs, ILs, and TNF) → vasospasm in spiral arteries → hypoxia and endometrial devitalisation
Haemostatic mechanisms will be activated including platelet plugs, coagulation cascade, and fibrinolysis
Endometrium shed down to basalis layer

20. Phases of the endometrium
Duration
2-8 days
Estrogen
Variable
Vascular growth
Progesterone
Fixed 14 days
Gland tortuosity & secretion, stromal oedema ,decidual reaction of the endometrium

21. Endometrial breakdown
Basalis layer remains Undergoes repair
Endometrium is protected from the lytic
enzymes in the menstrual fluid by mucinous
layer of carbohydrate products secreted from glands and stromal cells

22. Menstrual Fluid Autolysed functionalis layer Inflammatory exudate RBC
Proteolytic enzymes (mainly plasmin)
If rate and flow are high clots are formed

23. Hypothalamus Ant. Pituitary Inhibin E GnRh -VE FSH LH surge follicle
-ve feedback
Dominant follicle E
Ovulation
Estrogen

25. Cervical changes Follicular phase Luteal phase
Internal os: funnel shape
Tightly closed
Mucus: thin &watery
Thick & viscid
Stretchability: increased
Lost

26. Normal menstrual cycle
Menstrual cycle should be described according to
four specific symptomatic components
Frequency
Duration
Volume
Regularity

27. Normal Menstrual Cycle
Frequency (Length)
Mean is 28 days +/- 7 days
Menstrual cycle tends to shorten with age
Initially irregular
Duration of menstruation
Normal range: 4.5 – 8.0 days, Mean: 5 days
Prolonged >8 days, shortened < 4.5 days
With advancing age: duration decreases
Volume of menstrual blood loss (ml)
Range: 20 – 50 mls, Mean 40 ml
Heavy >80 ml; light < 5 ml