The document discusses several topics related to human reproductive cycles: 1. The ovarian cycle consists of the follicular and luteal phases, culminating in ovulation in the middle. The corpus luteum forms during the luteal phase and secretes hormones to prepare the uterus. 2. The menstrual cycle is controlled by ovarian hormones and has proliferative, secretory, and menstrual phases that regulate the endometrium. 3. Placentation begins with implantation and involves the formation of chorionic villi from the embryo and decidua from the endometrium to facilitate nutrient/waste exchange between mother and fetus without blood mixing. The placenta secretes important hormones throughout pregnancy.

1. Ovarian cycleOvarian cycle
Menstrual cycleMenstrual cycle
PlacentationPlacentation
Department of the Histology, Cytology and EmbryologyDepartment of the Histology, Cytology and Embryology
Tatiana GlobaTatiana Globa
State University of Medicine and Pharmacy “Nicolae Testemitanu”State University of Medicine and Pharmacy “Nicolae Testemitanu”

2. Ovarian cycle has 2 phasesOvarian cycle has 2 phases
• FOLLICULAR PHASEFOLLICULAR PHASE – consists of
the development of a primordial follicle
into a mature or Graafian follicle
• LUTEAL PHASELUTEAL PHASE – consists of the
formation of the corpus luteum, a
major-secreting gland
• At the middle of the ovarian cycle the
OVULATIONOVULATION takes place

3. Follicular Phase Luteal Phase

4. Endocrine Control
of Follicular
Development &
Ovulation
GnRH
(12 hrs. after LH peak)
-
Inhibin

5. Fate of Corpus Luteum (CL)
without fertilization
• FSH and LH release is inhibited by the
progesterone and estradiol released by
the CL
• Without LH, the CL lasts for ~14 days
before it degenerates

6. GnRH
LH maintains the
corpus luteum
Progesterone &
estrogen from CL
inhibits GnRH,
slowing the release
of FSH and LH
Without LH, the
CL degenerates
Junqueira et al. 8th
ed. Appleton and Lange
X X

7. Fate of Corpus LuteumFate of Corpus Luteum withwith
fertilization & implantationfertilization & implantation
• Chorionic gonadotropinChorionic gonadotropin (hCG) produced by the
placenta will support the CL for ~ 6 months
• also estrogen, IGF-I and II (from ovary), LH,
prolactin (from ant. pituitary) and insulin
contribute to formation and maintenance
• CL grows to a diameter of 5 cm
• Continues to secrete progesterone
• Decreases in size during last 3 months
• Begins to secrete relaxin in preparation for birth

8. Menstrual cycleMenstrual cycle
The endometrium is directly controlled by
OVARIAN hormones (estrogen,
progesterone), not by pituitary hormones
Menstrual cycle has 3 phases:
• Proliferative phaseProliferative phase is regulated by estrogens
• Secretory phaseSecretory phase is under the control of
progesterone
• Menstrual phaseMenstrual phase results from a decline in the
ovarian secretion of progesterone & estrogens

9. Stratum
Functionalis
Stratum
Basalis
Myometrium
Endometrium
(glands present;
dependent on
ovarian hormones
for appearance &
maintenance)
Uterine lumen

10. Arcuate
Arteries
(myometrium)
Uterine artery
Spiral arteries
(in endometrium –
dependent on
ovarian hormones for
growth &
maintenance)
Vascular Supply of Myometrium & EndometriumVascular Supply of Myometrium & Endometrium

11. Spiral arteries: dependent
upon estradiol for growth,
progesterone for
maintenance
Capillary bed with dilated
portions of capillary wall
(lacunae)

12. PROLIFERATIVE
PHASE
(days 4 – 14 of cycle)
MENSTRUAL CYCLE
4

13. Proliferative phase
- under control of
estradiol (follicular
phase of ovarian cycle)
- glands in s. basalis
under go mitosis
- stroma, glands,
spiral arteries grow
toward lumen
s. basalis

14. Proliferative phase: day 4 – day 14 of menstrual cycle

15. Hormonal control of
endometrial changes
during the menstrual
cycle:
SECRETORY PHASESECRETORY PHASE
(days 14 – 28 of cycle)

16. Secretory phase
- under control of
progesterone (luteal
phase of ovarian cycle
- uterine glands coiled,
larger lumens
- secrete glycogen,
mucin

17. Secretory phase: day 14 – 28 of menstrual cycle

18. Gestational hyperplasiaProliferative: day 9 Secretory: day 15 Secretory: day19
Pregnancy

19. Hormonal control of
endometrial changes during
the menstrual cycle:
MENSTRUAL PHASEMENSTRUAL PHASE
(days 1 – 4 of cycle)

20. Menstruation
At end of luteal phase of ovarian cycle,
Progesterone  Spiral arteries to constrict

21. Menstrual phaseMenstrual phase
- the involution of the corpus
luteum results from a decrease
in blood levels of steroid
hormones, leading to an
ischemic phase.
- a reduction in the normal blood
supply-causing intermittent
ischemia-and the consequent
hypoxia determine the necrosis
of the functional layer of the
endometrium, which sloughs off
during the menstrual phase.

22. Blastocyst
Blastocyst = inner cell mass
(embryo) +
outer shell
(trophoblast)
Fertilization
1
2
3
4
5
6
7
8
9
Morula

23. Placenta
Implanted in
the wall of the
uterus
Composed of
fetal portion
(chorion) and
maternal portion
(decidua)
Exchange of
gases, nutrients
waste products
without any
mixing of
maternal & fetal
blood

24. Functions of placenta
Act as
• respiratory organ
• excretory organ
• nutritive organ
• protective organ
• endocrine organ (progesterone, estrogens,
human chorionic gonatotropin, melanin
spreading factor, other hormones also
manufactured by the hypothalamus & pituitary.

26. This is a circumvallate placenta in which the membranes double back for a
short distance over the fetal surface when the chorionic plate is too small.
There may be increased fetal loss with this condition.

27. The maternal surface of a normal term placenta is seen here. Note that the
cotyledons that form the placenta are reddish brown and indistinct.

28. Placenta
• The morpho-functional unit is cotyledon. Placenta
has about 15-25 cotyledons.
• Proliferation of the trophoblast, growth of chorionic
mesoderm & blood vessel development give rise
to:
- primary chorionic villi – a mass of cells
- secondary villi – composed of a core of
mesenchyme surrounded by an inner layer of
cytotrophoblast & an outer layer of
syncytiotrophoblast
- tertiary villi – blood vessels have developed in
the cores

29. Inner cell mass
(embryo)
Uterine
lumen
Syncytiotrophoblast secretes
proteolytic enzymes
Maternal decidua

30. 9 days
Maternal
capillary
Uterine
lumen
Maternal decidua

31. Maternal
blood
enters
lacunae
Uterine gland
Syncytiotrophoblast
Uterine
lumen
Extraembryonic mesoderm
Cytotrophoblast
Maternal decidua
Blastocyst is now completely embeddedBlastocyst is now completely embedded
within the endometriumwithin the endometrium

32. Cytotrophoblast grows into syncytiotrophoblast:
(Maternal decidua)

33. Extraembryonic mesoderm invades primary villi:
Maternal decidua

34. (Intervillous spaces)
Fetal vessels grow into secondary villi:
Outer cytotrophoblast
shell
Maternal
decidua

35. 21 days
Maternal decidua
Human Embryology, Larsen, 1993 Churchill Livingstone

36. Fetal
Maternal
Small tertiary
villi will sprout
from larger ones
to increase
surface area for
exchange

37. Placenta – low magnification = Intervillous space
(maternal blood)

38. Villus from early pregnancy (during 3rd
Cytotrophoblast
Syncytiotrophoblast
Mesenchyme (embryonic CT)
Fetal capillaries

39. Villi from late pregnancy – 7th
month
By 4th
month, cytotrophoblast begins to thin out and is no longer obvious
syncytial knot

40. Placental barrier
• Syncytiotrophoblast
• Cytotrophoblast
• Basement membrane of trophoblast
• Connective tissue of the chorionic villus
• Basement membrane of endothelium
• Cytoplasm of endothelial cell

41. Placental Barrier
Intervillous space
(maternal blood)
O2, H2O,
electrolytes,
carbohydrates,
lipids, proteins,
antibodies
CO2, H2O, hormones,
metabolic waste
products

42. Placental structure and vascular dynamics
Fetal side
Maternal side

43. Placental Hormones
Syncytiotrophoblast secretes:
1. Human chorionic gonadotropin (HCG)
- detected 6 days after ovulation (pregnancy test)
- keeps CL alive
2. Placental lactogen – lactogenic and growth stimulating
properties for mammary gland (a.k.a. hCS: human chorionic
somatomammotropin)
3. Estradiol (made in cooperation with fetal adrenal cortex)
4. Progesterone
Cytotrophoblast also secretes:
IGF I and II; various other growth factors that stimulate
cytotrophoblast growth, plus hCG, estradiol,
progesterone

44. etal portion of
he placenta =
CHORION
. chorionic plate
. chorion
frondosum (villi)
. chorion laeve
(villi that were here
earlier have
degenerated)
Chorionic plate
Ham and Cormack, 8th
ed. J.B.Lippencott

45. Maternal portion of
he Placenta = DECIDUA
1. Decidua basalis
2. Decidua capsularis
3. Decidua parietalis
Ham and Cormack, 8th
ed. J.B.Lippencott

46. Decidual cells – glycogen, lipid for early embryonic nourishment;
later, produce decidual prolactin (trophic effects on CL), prostaglandins
(prevent immunologic rejection of fetus)of fetus), relaxin (dilates cervix and softens
pubic symphysis)
upper portion of decidua (near fetus)

48. Giant cells: multinucleated, trophoblast derivatives
that migrate into the decidua. Establish cleavage plane for
separation of placenta from endometrium after birth.

49. Fusion by 5th
month
(form cotyledons(form cotyledons
Placental septae