1. MENESTRUAL CYCLE
FERTILIZATION
IMPLANTATION

2. • Monthly menstruation is an obvious
marker that the various levels of
interaction between
-hypothalamus,
- pituitary,
- ovary &
-uterus are functional.

4. Endocrine cycle
Ovarian cycle
Endometrial cycle

6. GnRH…………………..Hypothalamus
Gonadotropins………..Pitutary
-FSH
-LH
Steroids…………………Ovary
-Estrogen
-Progestrone

7.  GnRH -Gonadotropin Releasing Hormone
 controlling factor for gonadotropin secretion
 synthesized by neurosecretory cells in the
hypothalamus
 carried by hypophysial portal system to anterior
lobe of pitutary
 Unique among releasing hormones b/se
1. simultaneously regulates the secretion of 2
hormones (FSH & LH)
2. must be secreted in pulsatile fashion to be
effective

9. Gonadotropins (FSH and LH)
-produced by the anterior pituitary
gonadotroph cells
-responsible for ovarian follicular stimulation
-FSH, LH, TSH, hCG all share identical α
subunits and differ only in the structure of
their β subunits

10.  The structural similarity between FSH, LH, and TSH.
The α subunits are identical and the β subunits differ.

11. Follicle Stimulating Hormone (FSH)
-stimulates development of ovarian
follicles
-stimulates production of estrogen by
follicular cells
Luetinizing Hormone (LH)
-trigger for ovulation ( release of
secondary oocyte)
-stimulates follicular cells & corpus
luteum to produce progesterone

13.  regulated at both endocrine and paracrine
levels
 Phases of ovarian cycle
-Follicular (pre ovulatory)
phase,
-Ovulation, and
-Luteal (post ovulatory) phase

14.  Oocytes in the ovary
- 7 million present during fetal life ,
- 2 million present at birth ,
- 400,000 present at the onset of
puberty, &
 >99.9 % of follicles undergo atresia
through a process of apoptosis
 Only 400 follicles are normally released
during female reproductive life

15. Development of ovarian follicle
characterized by;
-growth & differentiation of primary oocyte
-proliferation of follicular cells
-formation of zona pellucida
-dev’t of theca folliculi

16. Occurs around mid cycle
Triggered by a surge in LH production
Mechanism of ovulation………..

17.  After ovulation the walls of ovarian follicle & theca folliculi
develop in to glandular structure, corpus luteum, under LH
influence
 Corpus Luteum;
-secrets progesterone & some estrogen
-prepare endometrium for implantation
 Fate of corpus Luteum;
1) If the oocyte is fertilized
-enlarges to form corpus luteum of pregnancy
-placenta takes over function by around 8-10 wks
2) If no fertilization occurred
-involutes & degenerates 10-12 days after ovulation
-subsequently transformed in to white scar tissue in the
ovary….corpus albicans

19.  The functional layer of the endometrium is sloughed off
& discarded with the menestrual flow
 Origin of menstrual blood
-arterial bleeding greater than venous
 Mechanism of mensus….
rupture of arteriole of a coiled artery
hematoma formation
Superficial endometrium distends & ruptures
Fissures develop in adjacent functionalis layer
Blood & tissue fragments sloughed

20. Coincides with growth of ovarian follicles
Controlled by estrogen
2 to 3 fold increase in the thickness of
endometrium
Phase of repair & proliferation
Glands increase in number & length
Spiral arteries elongate
Length of cycle may vary among women

21.  Coincides with luteal phase of ovary
 Progesterone dependant
 Glandular epithelium secrete a glycogen rich
material
 Glands become wide, tortuous and saccular
 Endometrium thickens
 Spiral arteries become increasingly coiled
 Direct arteriovenous anastomosis are
prominent features
 Length of cycle usually fixed ( 14 days)

22. 1) If fertilization does not occur;
-the corpus luteum degenerates
-estrogen & progesterone levels fall &
the secretory endometrium enters an
ischemic phase
-menestruation occurs.

23. 2) If fertilization occurs;
-Decidualization (transformation of
secretory endometrium to decidua)
 DECIDUA
-a specialized, highly modified
endometrium of pregnancy
-a function of hemochorial placentation
 Types of decidua
1. Decidua basalis
2. Decidua capsularis
3. Decidua parietalis

24.  Duration of flow
1-8 days (5 on average)
 Frequency / cycle length
21-36 days (28 on average)
 Amount of blood flow
10-80ml (50 on average)
 Character of blood
Dark, non-clotting blood
 Degree of discomfort
No dysmenorrhea

25. CERVIX
VAGINA
BREASTS

27.  The union of egg & sperm
 Sequence of coordinated events
1. Passage of sperm through corona radiata
2. Penetration of the zona pellucida
3. Fusion of plasma membranes of the oocyte
& sperm
4. Completion of the second meiotic division of
oocyte & formation of female pronucleus
5. Formation of the male pronucleus
6. Fusion of pronuclei into a single diploid
aggregation of chromosomes…….the ootid
becomes a zygote

29. 10 microns (0.01mm)
(0.05 to 0.1 microns)
(0.5 to 1.5 microns)
(5 microns)
(5 to 8 microns)
(60 microns)
VIRUS
BACTERIA
RBC
LYMPHOCYTE
SPERM
SIZE COMPARISONS
100 microns
OVUM

30. SPERM NUCLEUS
EGG NUCLEUS
DIPLOID NUCLEUS
(syngamy - syn = together;
gamy = gametes)
FERTILIZATION ZYGTOTE ( = yoke)

31. Usual site is the ampulla of the fallopian
tubes
Results when intercourse occurs during
the 2 days preceding or on the day of
ovulation
Restores the normal diploid number of
chromosomes
Determines chromosomal sex of the
embryo

32.  Zygote
- a diploid cell with 46 chromosomes
-undergoes cleavage into blastomeres
 Morula..a solid mulberry-like ball of
cells
 The morula enters the uterine cavity
about 3 days after fertilization
 Gradual accumulation of fluid b/n the cells
of the morula ……..early blastocyst

40. The Blastocyst
1. Earliest stages of blastocyst;
-wall consists of single layer of ectoderm
2.As early as 4-5 days after fertilization;
-58 cell blastula differentiatesinto
5 embryo producing cells(inner cell
mass)
53 cells to form trophoblasts

41.  Takes place 6 or 7days after fertilization
 Divided in to 3 phases
1) APPOSITION
-initial adhesion of the blastocyst to the
uterine wall
2) ADHESION
-increased physical contact b/n the blastocyst &
uterine epithelium, &
3) INVASION
-penetration & invasion of syncytiotrophoblasts &
cytotrophoblasts in to the endometrium , inner
third of the myometrium & , uterine vasculature.

42.  Succesful implantation requires receptive
endometrium
 Uterine receptivity is limited to days 20-24 of
the cycle
 Implantation most commonly occurs on the
upper posterior uterine wall
 At the time of interaction with the
endometrium, the blastocyst is composed of
100-250 cells.
 By the 10th day the blastocyst becomes totally
encased with in endometrium

44. Hmmm…! Life is a journey!