Download BATCH 2014 Development of Placenta OUTLINE I. Implantation II

Reproduction Module
Development of the Placenta
13 January 2010
Dr. Bles Mantaring
OUTLINE
a.
It cannot be detached because this
will cause bleeding
b. Only treatment is the removal of
the uterus
iii. Abruption placenta
1. Premature separation of the placenta
from the uterine wall prior to birth
2. Obstetric problem will cause
a. Premature baby
b. Low birth weight
c. Likely cause hemorrhage for the
mother
d. Placenta breaks away, or “abrupt”
from the wall of the uterus too
early before the baby is born.
i. Premature birth
ii. Low birth weight
iii. Major blood loss in the mother
I. Implantation
II. Abnormalities in Placenta Delivery
III. Trophoblast
IV. Progesterone
V. Inhibition of Implantation
VI. Decidua
VII. Connecting Stalk
VIII. Chorionic Cavity
IX. Amniotic Fluid
X. Placenta
XI. Multiple Pregnancy
I.
II.
Group 04
Implantation
a. The blastocyst emerges from the Zona
Pellucida in a process called hatching
b. Blastocyst starts to embed in the
endometrium of the uterus
c. Starts at the end of the first week of
fertilization
d. Completed by the end of 2nd week
e. Trophoblast Differentiates into two layers
i. Syncitiotrophoblast
ii. Cytotrophoblast
Abnormalities Placenta Delivery
a. Normal Placenta
i. Fetus is delivered first, then the
umbilical cord and then the placenta
ii. Located at the posterior wall
b. Some abnormalities
i. Placenta previa
1. Implanted in the cervical canal,
impeding vaginal delivery of the
baby
2. The placenta is delivered first
rather than the baby, resulting to
hemorrhage; mother usually
undergoes abdominal delivery
ii. Placenta accrete
1. Placenta could invade the
maternal tissue up to the
permietrial lining of the uterus.
Thus, the placenta would be
difficult to detach sine this could
cause bleeding. The only solution
is for the uterus to be taken out
2. Placenta is attached to the uterine
mucosa
III. Trophoblast
a. Syncitiotrophoblast
i. Continuous multinucleate layer of
protoplasm
ii. No discernible cell boundaries
iii. Hormones secreted
1. Estrogen
2. Lactogen
3. Progesterone
a. Maintains secretory endometrium
iv. Human Chorionic Gonadotropin (HCG) =
most important
1. Increases in amount as go through
pregnancy
2. May double in multifetal pregnancy
3. Causes nausea/vomiting during first
trimester = this means you have high
levels of HCG
b. Cytotrophoblast – (or layer of Langhans)
i. Inner layer of the trophoblast
1. Interior to the syncitiotrophoblast in an
embryo
2. It serves to anchor the embryonic
chorion to the maternal endometrium
ii. Cytotrophoblasts are stem cells in the
chorionic villi
1. During differentiation, mononuclear
cytotrophoblast fuse together into the
multinucleated syncitiotrophoblasts
Alim. Alonzo. Anuran. Bautista. Biaco. Cang. Chan. Co. Sam. Sandel. Santos.
Page 1 of 5
BATCH 2014  Development of Placenta
i. When a female becomes pregnant, the
female undergoes changes in the
endometrium
ii. The transformation of secretory
endometrium to decida, and is dependent
on the action of estrogen and progesterone
and factors secreted by the implanting
blastocyst during trophoblast invasion
c. Decidual reaction
i. Cells undergo hypertrophy
ii. Endometrial accumulation of lipid and
glycogen in endometrial tissue
iii. Forms the three layers based on its
implantation: all the same, it just depends
on its relationship with the embryo
1. Decidua basalis – deep to conceptus, it
is where the embryo is implanted
2. Decidua capsularis – overlies the
conceptus
3. Decidua parietalis – remaning parts of
deciduas
d. Function of decidual cells
i. Provide an immunologically privileged site
for the conceptus
ii. Protects maternal tissue by preventing
uncontrolled invasion of syncitiotrophoblast
IV. Progesterone
a. Stimulates secretory phase prepares the
uterus for implantation
i. Secretory phase prepares the uterus for
implantation
b. Suppresses menstruation for the duration
of pregnancy
c. Inhibits uterine smooth muscle contraction
i. Allows the uterus to enlarge as fetus
grows
ii. Uterus will not contract even if it
stretches because of the hormones
produced during the pregnancy
d. Blocks T-Lymphocyte mediate immune
response
i. Prevents reaction with the non-cell of
the baby = baby is considered Non-Self
V. Inhibition of Implantation
a. Usually done on rape cases or women who
were assaulted or for unprotected coitus
b. Implantation can be inhibited by:
i. Large doses of estrogen (morning after
pill)
1. Inhibits ovulation by interfering
with transport of oocyte and
sperm in fallopian tube
2. Inhibits formulation of secretory
endometrium
a. There would be no
implantation
ii. Intra uterine devices
1. A small flexible plastic frame
inserted into the uterus through
the vagina
2. Causes an inflammatory response
in the uterine wall
3. The device prevents joining of
sperm and egg thus preventing
implantation
a. Because life is prevented,
church is against it
VI. Decidua
a. A specialized, highly modified
endometrium of pregnancy and is a
function of hemochorial placentation
b. Decidualization
Group 04
Primordial Uteroplacental Circulation: as the
syncitiotrophoblast erode the tissue it also erodes the
blood vessels, allowing blood to seep into the lacuna. This is
the start of the development of the placenta
Development of lacunae within the syncitiotrophoblast 
Syncitiotrophoblast erodes the maternal blood vessels 
Maternal blood containing oxygen and nutritive substances
flows into the lacuna (spaces)  primordial uteroplacental
circulation
VII. Chorionic Cavity
a. Develops during the 2nd week of embryonic life
b. Size is used to determine gestational age of
embryos
c. Components of chorion or chorionic
membrane
i. Extraembryonic mesoderm
ii. Cytotrophoblasts
iii. Syncitiotrophoblasts
d. Further development of the trophoblast:
i. Capillaries in tertiary villi make contact with
the following:
1. Capillaries in the chorionic plate
2. Capillaries in the connecting stalk –
there is now a communication
between embryo and placenta
Alim. Alonzo. Anuran. Bautista. Biaco. Cang. Chan. Co. Sam. Sandel. Santos.
Page 2 of 5
e.
f.
g.
h.
i.
j.
k.
l.
BATCH 2014  Development of Placenta
3. Forms the umbilical vessles
Types of villi in relation to the Chorionic
Plate:
i. Stem or Anchoring Villi
1. Villi that extends from the
chorionic plate to the deciduas
basalis
2. Mother villi
ii. Free or Terminal Villi
1. Villi arising from the sides of the
stem villi where exchange of
nutrients take place
2. Branches of the stem or anchoring
villi
Intervillous spaces – spaces between the
villi
Chorion fundosum – where the chorion
continues to develop
As pregnancy develops there will be an
absence of chorionic villi but at the
deciduas basalis where the fetus attaches
to the endometrium, the chorionic villi will
have profuse branching
The smooth area of the chorion at the
deciduas capitularis, is due to the
disappearance of the villi called the
Chorionic Laeve
The area in the decidua basalis which is
thick with villi is called the Chorion
Frondosum or Villous Chorion. This will
eventually form the placenta.
Cytotrophoblastic plate – stem villi where
there is branching and the presence of
terminal villi
Changes in the amniotic cavity in relation
to chorionic cavity
i. Amniochorionic membrane = fusion of
the amnion and chorion
ii. Growing amniotic cavity obliterates the
chorionic cavity
iii. When a pregnant women’s water
breaks the water is amniotic fluid
flowing out
VIII. Connecting Stalk
a. A thick layer of mesoderm that suspends
the embryo together with the amnion and
yolk sac suspended in chorionic cavity
b. Becomes the umbilicus
c. Chorionic plate
i. Extraembryonic mesoderm lining the
inside of the cytotrophoblast
d. Types of chorionic Villi in relation to the
Trophoblast (Syncitio and Cyto)
Group 04
i. Primary Chorionic Villi
1. Cytotrophoblast proliferate and
produce cell extensions into
syncitiotrophoblast
2. Covers entire chorionic sac
3. Start of the placental villi
4. Core of cytotrophoblasts
ii. Secondary Chorionic Villi
1. Primary chorionic villi acquire
mesenchymal core
2. Outermost layer will be
syncitiotrophoblast
iii. Tertiary Chorionic Villi
1. Development of capillaries in
secondary chorionic villi
2. Found in term of placentas
3. Definitive placenta villi
4. Under the microscope, look for the
presence of blood vessels
e. The inner Cytotrophoblasts proliferate up to
the Syncitium to form primary chorionic villi
primary would form mesenchymal core which
would be the secondary chorionic villi -->
capillaries would invade the lacuna As villi
develop, lacuna would become the primordium
of the intervillous space  Cytotrophoblast
proliferate during pregnancy and may
penetrate the syncitium, enclosing the
chorianic sac forming the outer
cytotrophoblastic shell. This anchors chorionic
sac to the endometrium.--> Shell surrounds the
trophoblast attaching the chorionic sac to the
endometrium
IX. Amniotic Fluid
a. Increases in the amount up to term pregnancy
b. Functions
i. Thermoregulation – keeps the baby warm
ii. Provides lubrication preventing the baby’s
body parts from growing
1. Allows for fetal movement
2. Acts like liquid shock absorber for the
baby by distributing any force that may
push on the mother’s uterus
a. Allows the baby to float around so
baby’s body parts wont stick to
each other
b. For the mother not to feel to too
much pain
c. For late pregnancy, the mother
usually complains of pain since
there is a decreasing amount of
amniotic fluid
Alim. Alonzo. Anuran. Bautista. Biaco. Cang. Chan. Co. Sam. Sandel. Santos.
Page 3 of 5
BATCH 2014  Development of Placenta
X. Placenta
2. Wedge shaped areas of the decidua
a. Primary site of nutrient and gas exchange
formed by the erosion of the decidua
between the mother and the fetus
basalis
b. Two components
3. Divides the placenta into cotyledons
i. Fetal part – develops from the chorionic
sac (chorion fundosum)
*Blood circulation in the placenta: Uterine artery will end in
ii. Maternal part – derived from the
spiral arteries as it penetrates the endometrium ; Spiral
deidua basalis
arteries – very sensitive to changes in hormones (i.e.
c. Histologic Importance
estrogen, progesterone)  blood from spiral arteries will
i. Maternal side – cobblestone
bathe the villi (nutrient exchange)  blood from fetus will
appearance with cotyledons
go back to endometrial veins
ii. Fetal – white shiny
d. Functions
vi. Placental Barrier
i. Exchange of gas by simple diffusion
1. Components
ii. Exchange of nutrients and electrolytes
a. Syncitiotrophoblast
1. Increases as pregnancy advances
b. Cytotrophoblast
iii. Transmission of maternal antibodies
c. Connective tissue of villus
1. IgG transported from mother to
d. Endothelium of fetal capillaries
fetus at 14 weeks
vii. With aging
iv. Hormone production
1. Decrease number of cytotrophoblast
1. Progesterone
a. The barrier thins out, allowing
2. Estrogenic hormones (estriol)
easier flow of nutrients through the
a. Stimulates growth of uterus
placental barrier
and mammary gland
2. Presence of syncitial knots
3. HCG
a. Nuclei of basement membrane
a. Maintains corpus luteum
grouped together
4. Placental Lactogen
3. Deposition of fibrinoid material on the
a. Give fetus priority on maternal
surface of the villi
blood glucose
4. EARLY PLACENTA
b. Promotes breast development
a. Histological
for milk production
i. RBC are nucleated
5. Metabolism of glycogen and fatty
ii. Presence of cytotrophoblasts
acids
5. TERM PLACENTA
a. Transport of gases and
a. RBC lack nucleus
nutrients
b. Discoid
b. Passive or facilitated diffusion
c. Thicker at center (due to umbilical
c. Active transport
cord) and tapers at sides
d. Pinocytosis
d. Heavy, weighs about 500-600g (1/6
6. Endocrine secretion
of fetal weight)
a. HCG
e. 15-20 cm in diameter and 2-3 cm in
i. Secretion begins as early as 8
thickness
days postovulation
ii. Basis of pregnancy test
Maternal surface:
Fetal Surface:
iii. Acts on ovary to maintain
1. cobblestone appearance
1. attachment of
corpus luteum during
2. presence of cotyledons
umbilical cord
pregnancy (due to
separated by grooves that
 With 2
progesterone; maintained for
were formerly occupied by
arteries and
2 months)
placental septa
a vein
b. Progesterone
 Syncitiotrophoblast
 If there is
v. Placental Septa
invades the uterine wall
only 1
1. Syncitiotrophoblast does not
and leaves a septa of
artery and 1
uniformly erode the decidua
decidua basalis in
vein, there
a. It leaves some parts of the
between. Septa does
is usually an
decidua called the placental
not reach the chorionic
abnormality
septa
plate and marks the
2. smooth and shiny
Group 04
Alim. Alonzo. Anuran. Bautista. Biaco. Cang. Chan. Co. Sam. Sandel. Santos.
Page 4 of 5
BATCH 2014  Development of Placenta
area of the cotyledon
(15‐20 cotyledons)
 Spiral arteries –
openings into the
cytotrophoblastic shell
resulting in blood
entering the
intervillluous spaces in a
pulsatile manner
3. Chorion is nearer to the
maternal side
(amniochorionic
membrane)
3. covered by
amnion
4. chorionic vessels
seen radiating from
the umbilical cord
5. Amnion is nearer
to the fetal side
XI. Multiple Pregnancy
a. Fraternal Twins
i. Fertilization of two oocytes
ii. Separate implantation
1. Separate placenta and amniotic
cavities
b. Identical Twins
i. Derived from a single zygote that
divided into two
ii. Sharing of placenta and amniotic cavity
depends on what developmental stage
the zygote divided
iii. Kinds of identical twinning
1. Dichorionic diamniotic = fraternal
twins
2. Monochorionic diamniotic =
identical twins = 1 chorion,
diamniotic
3. Monochorionic monoamniotic =
identical = high risk of congenital
anomalies
*Be able to identify the sides of the placenta and the
umbilical chord. Placenta is thicker in the center and
tapers at the ends.
Group 04
Alim. Alonzo. Anuran. Bautista. Biaco. Cang. Chan. Co. Sam. Sandel. Santos.
Page 5 of 5