Placenta And Fetal Membranes Flashcards
4 fetal membranes
- Chorion
- Amnion
- Umbilical vehicle
- Allantois
2 parts of the placenta
- FETAL PART : chorionic sac (outermost fetal membrane)
2. MATERNAL PART : from endometrium (most functional part of placenta) = decidua
What connects placenta circulation to fetal circulation
Umbilical cord vessels
Site of blood and nutrient exchange from mom and fetus
Placenta
Decidua and 3 parts
Functional part of endometrium, leaves with baby
- Decidua basalis
- Decidua Capsularis
- Decidua Parietalis
Decidua Basalis
Deep to conceptus, where blastocyst implants into endometrium
Maternal part of placenta
BABY + PLACENTA
Decidua Capsularis
Superficial and overlies the conceptus
CHORION
Decidua Pareitalis
Remaining parts of the decidua
WALLS OF UTERUS
Decidual Reaction
Done by the decidua basalis cells that undergo massive lipid and glycogen accumulation and look pale = nutrients for embryo
when do trophoblasts differentiate and to what
10th day, as blastocyst is embedded into endometrium
- Cytotrophoblast (inner)
- Syncytiotrophoblasts (outer)= invades and displaces decidual cells —-> decidua basalis
Lacunae appear
In the syncytiotrophoblast
Fill with blood and uterine secretion, forms networks
Primordial Uteroplacental Circulation
O2 and nutrients pass to embryo by diffusion through lacunae networks bathing the embryo
(Before any Blood supply network has established)
The Amnion is
Thin tough membrane around fetus and amniotic fluid
= will eventually grow to X chronic cavity and line the umbilical cord
Where do amnioblasts come from
From the Epiblast
Amniotic Fluid
Cushion fetus, reg temp, increases with gestation
(Has aa, carbs, fats, enzymes, Hs., salts, ions, steroids)
Over time GIGU and RESP takes over
How much amniotic fluid at birth
700ml-1000ml
Extraembryonic mesoderm (hypoblast) consists of
- Extraembryonic somatic mesoderm : lines trophoblasts and over amnion
- extraembryonic Splanchnic mesoderm : around umbilical vesicle
- Extraembryonic Ceolom : around amnion and umbilical vesicle
Chorionic sac 3 components
Cytotrophoblasts + Syncytiotrophobalsts + extraembryonic somatic mesoderm
Poly Hydraminos
Excessive fluid
CAUSES: CNS + genetic deformities + GI blockage
ABD pain, swelling and bloating,breathlessness, PROM risk, uterus grows too big
*Premature rupture of membranes = PROM
Oligohydramnios
Not enough fluid (<400ml),
CAUSES : renal agenesis, pulmonary hypoplasia,
Club foot, maternal HTN
Placenta 3 critical components
Villous Chorion = fetal part sticking into decidua basalis
Chorionic villi
Decidua basalis = maternal part
Cytotrophoblasts do what after implantation to form the placenta at the decidua basalis site
- It proliferates to make the CHORIONIC PLATE right below the villus chorion (fetal part)
- Extends extensions through the syncytiotrophoblasts to attach to decidua basalis = CYTOTROPHOBLASTIC SHELL
- Encloses the lacunae networks inside the villus chorion forming the INTERVILLOUS SPACE
Intervillous space
Forms lacunae network and site of blood with the fetal villi sticking in to it
Placental Septa
Decidua erosion that happens as the cytotrophocytes that enclose the lancunea network eroded villi by maternal decidua basalis (on either side of villi)
Parts that are not eroded forming the villi = Cotyledons
Which weeks do intervillous space of placenta contain maternal blood due to the decidual erosion
Week 11-14
(In areas that the villous chorion and decidua basalis connect and form openings into each other) * BY spiral arteries
Primary Chorionic Villi
When cytotrophoblasts first grow into the syncytiotrophoblasts
Week 2 end
And then forms small columns (week8) which become SMOOTH and VILLOUS chorion
* cytotrophoblasts core and covered by syncytiotrophoblasts
The smooth vs villus chorion
the decidua basalis = villous chorion
The decidua Capsularis = smooth chorion (columns degenerate)
The Secondary Chorionic Villi
Extraembryonic mesoderm grows into the primary villi (WEEK3)
Core : Extraembryonic mesoderm (fetal CT)
Covered by cytotrophoblasts and syncytiotrophoblasts
Tertiary Chorionic Villi
Some of the Extraembryonic mesoderm have become BVs
CORE : Capillaries and CT
Then cytotrophoblast layer
Then syncytiotrophoblasts layer’
*Late pregnancy = cytotrophoblasts are lost slowly and syncytiotrophoblasts organize into syncytial knots
Tertiary Chorionic Villi have 3 types to BV villi inside
all from the villus chorion
MAIN STEM VILLI : extend from chorionic plate
*BRANCH VILLI : extend from main stem villi to increase SA, (main exchange)
ANCHORING VILLI : attach to the maternal tissues on the cytotrophoblastic shell
Cotyledons contain
2 or more main stem villi + many branch villi
As the the chorionic villi are formed there are some changes happening to the decidua
- Villous chorion = placenta site
Capsularis = smooth chorion - Capsularis part bulges into the uterine cavity eventually hitting the other uterine wall
- Casularis degenerates : Amnion and Chorion fuse = Amniochorionic membrane
- Amniochorionic membrane fuses with decidua paietalis on opposite wall facing the vagina opening
Before 20 week
Syncytiotrophoblasts, cytotrophoblasts, CT in villi, endothelium of fetal capillaries
After 20 weeks
Syncytiotrophoblasts, CT in Villi, endothelium of fetal capillaries
(Lost cytotrophoblast) - late pregnancy
What CANT cross the placenta membrane
Protein Hs. (AP, PP)
Bacteria
aa like structured drugs (methyldopa)
What CAN cross the placental membrane
Nutrients : H2O, glucose, aa, VIT, electrolytes
H. : testosterone, progestins, T3/T4
IgG
Insulin (some)
Waste
Drugs + alcohol
Infections of : Varicella, rubella, measles, herpes, listeria….
What is inside the umbilical cord
Enclosed by amnion and inside is mucous tissue = WHARTON’S JELLY
- 2 Umbilical A.s (deoxygenated)
- 1 Umbilical V (80% oxygenated)
X Umbilical Artery
By chromosome or fetal anomalies
Can impact 3rd stage labor
Agenesis or degraded one of A.s, detected before birth
Placenta Previa
Placenta implants in lower uterine segment or cervical
= 3rd trimester bleeding
= high risk if you have had prior placental previa or c-section
Placenta Accrete/a
Partial or complete absence of the decidua = villous chorion adheres to myometrium directly
= placenta does not separate at birth
= sever and life threatening postpartum bleeding
Hydatidiform Mole
Replacement of normal villi by dilated or hydropic (edematous) translucent vesicles
- Partial Mole
- Complete Mole
Partial Mole
Portions of villi are edematous, capillaries can be seen in the villi
Fetal tissue can be found
Ovum fertilized with 2 sperm (69XXY or 92XXXY)
Complete Mole
All villi enlarged, covered with trophoblast invasion
No fetal tissue
Fertilization of blighted ovum ——> all DNA is paternal (2 sperm or 1 duplicated sperm) (46XY, 46XX)
Invasive Mole
Complete mole (which has no genetic info) that penetrates or perforated the uterine wall = hemorrhaging
Dx: high hCG
Sx: female has + pregnancy test and no fetal tissue in ultrasound
Tx: chemotherapy
Gestational Choriocarcinoma
Highly invasive tumor from trophoblast cells
50% of molar pregnancies
Dx: High hCG with no uterine enlargement
Tx: chemotherapy and other agents combined
Monozygotic Twins
SAME chorion sac
Divides at :
2-8 cell (0-72hr) ——> 2 amnion, 2 chorion * MOST separate placentas
Blastocyst (4-8 days) ——> 2 amnion, 1 chorion
Implanted (9-12 days) ——> 1 amnion, 1 chorion
Most monozygotic twins divide when
from embryoblast at blastocyst (65%)
35% divide at 2 morula stage - own chorionic and amniotic sacs
Dizygotic Twins
From 2 zygotes (2 amnions and 2 chorions) =Fraternal twins
Implant separately = 2 chorions, 2 amnions
Adjacent Implantatin = 2 amnions, 2 fused chorions, 2 placentas
