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
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
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
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.
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.
25.
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
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)
47.
48. Giant cells: multinucleated, trophoblast derivatives
that migrate into the decidua. Establish cleavage plane for
separation of placenta from endometrium after birth.
Estradiol has negative feedback on FSH release and almost stops LH secretion – however both are still synthesized and stored in the gonadotropes. At midcycle, the pituitary gonadotropes become more sensitive to GnRH and the graafian follicle releases a maximum level of estradiol, which now effects a positive feedback effect on GnRH, causing gonadotropes to release LH and some FSH as well
Relaxin causes dilation of cervix, softens symphysis pubis in preparation for birth
Branches of arcuate arteries enter basalis layer, where they ascend to functionalis layer as spiral arteries.
Lacunae are thin-walled, dilated segments of the capillary bed. Spiral arteries give off numerous capillaries.
The layer of trophoblast closest to the inner cell mass is called the cytotrophoblast and consists of an irregular layer of ovoid, mononucleated cells thatundergo extensive proliferation.
At day 8, the portion of the cytotrophoblast that pushes into the endometrium differentiates into the syncytiotrophoblast. The syncytiotrophoblast is formed by the fusion of cytotrophoblast cells, forming a multinucleated syncytium possessing microvilli at its surface.
The syncytiotrophoblast forms spaces, or lacunae which will shortly become filled with maternal blood
The syncytiotrophoblast invades the endometrium (decidua) and ruptures the maternal arterial and venous blood vessels. The maternal blood flows from the arterial vessels into spaces (lacunae) that form at day 9 within syncytiotrophoblast. The maternal blood is drained by the ruptured veins and returns to the mother’s circulatory system.
By day 13, the cytotrophoblast cells grow into the syncytiotrophoblast to form primary villi.
By day 16, the extraembryonic mesoderm derived from the inner cell mass invades the center of the primary villi, producing secondary villi.
By day 21, fetal vessels (part of the umbilical circulation) grow into the secondary villi, forming tertiary villi.
Cytotrophoblastic shell anchors blastocyst to decidua – cytotrophoblast cells migrate out from tertiary villi to surround blastocyst
Placenta Functions as lungs, GI tract and kidneys for the fetus!
Chorion laeve forms chorionic sac
decidual prolactin has trophic effects on CL; relaxin softens cervix and pubic symphysis; prostaglandins help to prevent immunologic rejection of fetus
