Physiology of Menstruation

1. Dr. Salini Mandal B.G.
Lecturer
Dept of OBG
FMHMC
Menstruati
on

2. DEFINITION…
• Menstruation is the visible manifestation of
cyclic physiologic uterine bleeding due to
shedding of the endometrium.

3. MENSTRUAL CYCLE
• 28 + 7 DAYS
• Flow : 4 + 2 days
• Volume : 5 – 80ml
• Regulated by Hypothalamus – Pituitary –
Ovarian Axis

4. • Menstrual cycle can be explained in 2 cycles which
occur concurrently.
– THE OVARIAN CYCLE
– THE UTERINE CYLCLE
• OVARIAN CYCLE:
– Follicular phase, Ovulation, Luteal phase
• UTERINE CYCLE:
– Regenerative phase, Proliferative phase, Secretory
phase, Menstrual phase

6. THE OVARIAN
CYCLE

8. FOLLICULAR
PHASE
THE OVARIAN
CYCLE

10. PRIMORDIAL FOLLICLE
• Originate in the Endoderm
• Migrate to the genital ridge at 5 -5 6 weeks
• Maximum at 16 – 20 weeks : 6 – 7 million
• At birth : 2 million
• At puberty : 0.3 to 0.5 million
• Only 400 -500 follicles ovulate during a woman’s
reproductive years

11. • The primodial follicle is nongrowing and consists of
an oocyte, arrested in the diplotene stage of meiotic
prophase, surrounded by a single layer of spindle –
shaped granulosa cells

12. • The initial recruitment and growth of the primordial
follicles is gonadotropin independent and affects a cohort
over several months
• The total duration of time to achieve pre ovulatory status is
approximately 85 days
• First visible signs of development are
– Increase in the size of oocyte
– granulosa cells becoming cuboidal

13. The Pre antral Follicle
• Oocyte enlarges and is surrounded by a
membrane(acellular barrier) produced by the
follicular fluid, the zona pellucida.
• The granulosa cells undergo a multilayer proliferation
as the theca layer continues to organize from the
surrounding stroma.

14.  The granulosa cells of the preantral follicle synthesizes
all 3 classes of steroids
 Estrogens are produced more than androgens or
progestins
 An aromatase enzyme system converts androgens to
estrogens and is a factor limiting ovarian estrogen
production.
 Aromatization is induced or activated through the action
of FSH.

15. The Preovulatory Follicle
• Granulosa cells in the preovulatory follicle
enlarge than the theca cells
• And theca becomes vacuolated and richly
vascular, giving the preovulatory follicle a
hyperemic appearance.
• The oocyte proceeds in meiosis, approaching
completion of its reduction division.
• Approaching maturity, the preovulatory follicle
produces increasing amounts of estrogen.
• Estrogen peaks approximately 24 to 36 hours
prior to ovulation.

18. • The onset of the LH surge occurs when the peak
levels of estradiol are achieved.
• In providing the ovulatory stimulus to the selected
follicle, the LH surge seals the fate of the remaining
follicles, with their lower estrogen and FSH content,
by further increasing androgen superiority.
• LH promotes luteinization of the granulosa in the
dominant follicle, resulting in the production of
progesterone

19. • A threshold of LH concentration must be maintained
for at least 14 to 27 hours in order for full maturation
of the oocyte to occur.
 Usually the LH surge lasts 48 to 50 hours

20. Ovulation
• Dominant follicle shortly before ovulation reaches
the surface of the ovary.

23. Luteal phase
• PROLIFERATION
• VASCULARISATION
• MATURATION
• REGRESSION

24. PROLIFERTION
• Collapsed walls of the empty follicle form
convolutions. The opening through which the ovum
escapes soon becomes plugged with fibrin.
• Granulosa cells undergo hypertrophy without
multiplication
• Cells become large, polyhedral with pale nuclei and
frothy cytoplasm

25. Vascularisation
• Within 24 hrs of the rupture of the follicle small
capillaries grow into granulosa layer towards the
lumen accompanied by lymphatics and fibroblasts.

26. Maturation
• By 4th day, luteal cells have attained the maximum
size.
• After 7.8days of ovulation, the corpus luteum attains
a size of about 1.2cm and reaches its secretory peak.
• Theca cells hypertorphy…
• Luteal cells become greatly enlarged and develop
lipid inclusion, giving the cells a distinctive yellowish
colour.

27. REGRESSION
• On the day 22 – 23 of cycle, retrogression starts.
• First evidence of degeneration is the appearance of
vacuolisation in the cells.
• There is deposition of fat in the lutein cells and
appearance of hyaline tissue between them.
• The lutein cells atrophy and the corpus luteum
becomes corpus albicans..

29. UTERINE
CYCLE

30. ENDOMETRIUM
• Lining epithelium of the uterine cavity above the
level of internal os.
• It consists of surface epithelium, glands, stroma and
blood vessels.
• 2 layers:-
– Basal zone
– Functional zone

33. BASAL ZONE
• About one-third of the total depth of the
endometrium and lies in contact with the
myometrium.
• Consists of stromal cells which stain deeply and are
compactly placed.
• The base of the endometrial glands extends into the
layer
• Supplied by the basal arteries

34. • Uninfluenced by hormones  so no change observed
during the cycle.
• After shedding of the superficial part during
menstruation, the regeneration of all the components
occurs from this BASAL ZONE.

36. FUNCTIONAL ZONE
• Under influence of the fluctuating cyclic ovarian
hormones, oestrogen and progesterone.
• 4 cycles:
– Regenerative
– Proliferative
– Secretory
– Menstruation

37. STAGE OF REGENERATION
• Regeneration of the endometrium starts even before
the menstruation ceases and is completed 2 – 3days
after the end of menstruation.
• The cubical surface epithelium is derived from the
gland lumina and stromal cells.
• New blood vessels grow from the stumps of the old
one.
• The glands and stromal cells are regenerated from
the remnants left in the basal zone

38. • Glands are lined by cuboidal epithelium and lie
parallel to the surface.
• Stromal ground substance re-epands.
• Thickness – 2mm

39. STAGE OF PROLIFERATION
• Extends from 5th or 6th day to 14th day (till ovulation).
• Changes occur due to rise in level of ovarian
oestrogens.
• Proliferation of all elements  first slowly then
rapidly.
• Glands become tubular and lie perpendicular to the
surface.
• Epithelium becomes columnar with nuclei at the
base.

40. • Epithelium of one gland becomes continuous with
other.
• Stromal cells become spindle (mitosis)
• Spiral vessel etend unbranched to a region below he
epithelium where they form loose capillary network.
• Subepithelial congestion visible.
• Thikness 3-4 mm

41. Secretory phase
• Due to combined effect of estrogen and
progesterone from corpus luteum after ovulation.
• Endometrium contains receptors for progesterone
which are induced by estrogen.
• All components display growth. It begins on day 15
and ceases 5 – 6 days prior to menstruation.
• Surface epithelium becomes more columnar and
ciliated at places

42. • Glands increase in size. Lining epithelium becomes
taller with appearance of secretion containing
glycogen between the nuclei and the basement
membrane (subnuclear vacuolation).
• Earliest evidence of ovulation
• This persists until about 21st day of cycle.
• The intracellular secretion then enters the gland
lumina on the way to the uterine cavity pushing the
nuclei back to the basement membrane giving saw-
toothed appearance.
• Blood vesels undergo marked spiralling.

43. • Stromal cells – swollen, large and polyhedral and
after 21st day tend to collect more superficially
around the neck of the glands.
• Thicknes – 5 - 6mm
• Endometrial growth ceases 22nd or 23rd day prior to
an infertile cycle. (due to the dehydration of the
glands)
• Capillaries and vessels are engorged.24 – 48hrs prior
to menstruation  changes are pronounced.
Withdrawal of hormones  intense spasm of
vessels.

44. MENSTRUAL PHASE
• Degeneration and casting off of an endometrium
prepared for a pregnancy.
• Regression of the corpus luteum with the fall of
oestrogen and progesterone  preceding feature
• No hormone  regressive changes.
• Mainly vascular origin.
• Stasis of blood and spasms of arterioles  damage
of arteriolar walls.

45. • Phase of relaxation leads to escape of blood out of
the vessels through the damaged walls.
• Degenerative process is rapid and involves all the
components of the functional damages layer.
• Blood along with the functional layer is shed into the
uterine cavity.
• Blood coagulates in the uterine cavity but soon
liquifies by plasmin.
• The flow stops as a result of combined effect of
prolonged vasoconstriction, myometrial contraction
and local aggregation of platelets with deposition of
fibrin.
• Resumption of estrogen secretion  leads to clot
formation over the vessels.

49. MENSTRUAL SYMPTOMS
• PREMONITORY SYMPTOMS:
– Pelvic discomfort
– Backache
– Fullness of the breasts or mastagia
– Headache and depression(may be).
• Bleeding + colicky pain at the beginning. (if more –
dysmenorrhoea)

50. CERVICAL CYCLE
FOLLICULAR PHASE LUTEAL PHASE
•Internal os – funnel shaped
• Mucus - thin and watery
•Stretchability – increased to
beyond 10 cm
•Fern tree pattern appearance
•Glycoprotein network – parallel,
thus facilitating sperm penetration
•Glandular epithelium - taller
• tightly closed
•Thick and viscid
•Lost
•Lost
•Interlacing bridges, preventing
sperm penetration
•Glands – more branched

51. VAGINAL CYCLE
FOLLICULAR PHASE LUTEAL PHASE
•Cytology : showing
preponderance of superficial
large cornified cells with
pyknotic nuclei.
•Background of the smear -
clear
•Preponderance of
intermediate cells with folded
edges (navicular cells)
•Dirty due to presence of
leucocytes and bacilli

52. GENERAL CHANGES
PREOVULATORY OVULATORY PREMENSTRUAL
•No symptom •Pain abdomen on
either iliac fossa
•Slight vaginal
bleding
•Mucoid vaginal
discharge
•Irritability, lethargy,
constipation
•Acne
•Pelvic discomfort
•Abnormal gain in
weight
•Mastalgia