Implantation and Placentation Flashcards
What is the trophoblast, chorion and amnion?
Trophoblast – cells of the ? that invade the ? and ? (Days ?) and secrete ?
Chorion – becomes the ? (? tissue)
Amnion – layer that ultimately becomes ?
Trophoblast – cells of the blastocyst that invade the endometrium and myometrium (Day 5-6) and secrete ßhCG
Chorion – becomes the placenta (placental tissue)
Amnion – layer that ultimately becomes amniotic sac
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What are the functions of the placenta?
?: secretes ?, ?, ? and ?
Transfers maternal ? and ? required to develop the baby. ( ? are transported so baby is born with ? )
Quick removal of ? (?, ?, ?, and ?)
Acts as a barrier from ?, etc.
Steroidogenesis: secretes E2, P4, cortisol and HPL (human placental lactogen)
Transfers maternal O2, carbs, fats, AAs, vitamins, minerals and Abs required to develop the baby, passive immunity
Quick removal of waste (CO2, urea, NH4, and minerals)
Acts as a barrier from bacteria, viruses, drugs, etc.
4 adaptations of the placenta that make it good at its job?
Huge maternal ?
Huge reserve in ?
Very high ?
Transfer system is ?
Huge maternal uterine blood supply: delivered at a low pa (gently over the villi submerged in the sea of maternal blood)
Huge reserve in function in case of blood loss or defects
Very high SA in contact with maternal blood for better exchange between mother and fetus
Transfer system in the placenta is highly adapted and efficient
Describe the placenta from day 14-15
blastocyst ? into ? + now is starting to ?
? = large ? surrounding ?
? = precursor to ?
? = outer ? layer that grows out + invades into ?
? = inner ? cell layer which will differentiate into ?
? = filled with maternal ?
? = makes ?
Placenta on day 14-15: Blastocyst completely embeds into endometrial tissue (white) + starts to develop further
Gestational sac (black) = large fluid cavity surrounding embryo
Connecting stalk = precursor to umbilical cord
Syncytiotrophoblast = outer trophoblast layer that grows out + invades into endometrium decidua
Cytotrophoblast = inner mononuclear stem cell layer which will differentiate into syncytiotrophoblast
Lacuna= filled with maternal blood – exchange surface from mother–> embryo
Extraembryonic mesoderm = makes connective tissue, BVs, muscles, etc.
What happens by week 8?
trophectoderm, mature trophectoderm
What does the chorion attach to?
As the baby grows, it ?
By week 8 of pregnancy, the outermost trophectoderm differentiates into two distinct regions:
Trophectoderm thins + regresses to form the chorion laeve
The mature trophectoderm that develops into the placenta is the chorion frondosum.
The chorion attaches to decidua basalis
As the baby grows, it obliterates the uterine cavity –> whole uterine cavity is filled by the baby in the amniotic sac with the placenta like a disk on one side
These diagrams show cross sections of villi. Explain what is happening in these images
Everything below the border of the invading syncytiotrophoblast layer is maternal blood (lacuna)
? go first – like a glove
? come next into the glove. Functions as ?
Finally, ? comes in to the glove. Develops into ?
Lacuna get closed off by ?–> maternal BVs supply ?, and ?
Syncytiotrophoblast go first – like a glove
Cytotrophoblast come next into the glove. Functions as a support structure for the developing placenta.
Finally, extraembryonic mesoderm comes in to the glove. Develops into blood vessels
Lacuna get closed off by syncytiotrophoblast layers and cytotrophoblast–> maternal BVs supply lacuna, and interacts w embryonic BVs exchange substances
What is the vs membrane and when is it formed?
The VSM cells ? + get more ? to ?
? villi further ↑ ?
They sit in ?
? cell thick to allow ?
Vasculosyncytial membrane (VSM) is the primary site of foetomaternal exchange
Formed when syncytiotrophoblast surrounds the terminal villi and makes close contact with capillaries.
The VSM cells sprout and get more convoluted to ↑ SA. Terminal villi further ↑ SA massively
They sit in maternal blood
One cell thick to allow quick, efficient transfer
Label and describe the placenta
? artery + ? artery carry ? blood into the ?, then picks up ? from the maternal blood in the ?, & travels back up in the ? back to the foetus : This is opposite to ? arteries & veins
Placental steroidogenesis begins very early on at about ? weeks
Foetal artery and umbilical artery carry deoxygenated blood into the placenta, picks up oxygen from the maternal blood in the placenta, and travels back up in the veins to the foetus
This is opposite to adult arteries and veins
Placental steroidogenesis begins very early on at about 7-8 weeks
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2 functions of the amniotic cavity?
The baby needs fluid to enable ? and developing ?
Protection: physical barrier around the embryo. Has antimicrobial/anti-inflammatory properties and protects against ascending infections (UTI, BV, STIs)
Homeostasis: temp., ion control, fluid, etc. Fluid – extremely important as its vital for lung and limb development!!
The baby needs fluid to enable kicking and developing limb range of motion, as it allows the fetus to move and exercise its muscles.
What happens if amniotic fluid ruptures early in pregnancy?
If amniotic fluid ruptures early in pregnancy, ? + ? dont develop and the baby born w severe ? (fluid needed for this as baby ? through that effectively). There will also be ?
This is a disaster and can kill the baby.
If amniotic fluid ruptures early in pregnancy, lungs and limbs do not develop and the baby born w severe pulmonary hypoplasia (fluid needed for this as baby breathes through that effectively). There will also be limb contractures, where the limbs are fixed in a bent or abnormal position.
This is a disaster and can kill the baby.
Image shows development of the amnion:
? = blue/pink/yellow line
If someone is scanned early on in pregnancy, a ? will be seen
Firstly, neural fold develops from ?
The ? just above it gets pulled around
The ? sac regresses at about ? weeks
Image shows development of the amnion:
Trilaminar disk = blue/pink/yellow line
If someone is scanned early in pregnancy, a yolk sac (black circle) will be seen
Firstly, neural fold develops from blue line (ectoderm)
The amniotic sac just above it gets pulled around
The yolk sac regresses at about 12 weeks (not seen at the genetic disorder screening nuchal scan)
Why do most miscarriages occur? 2 reasons, and describe them both in detail
PE is caused by inefficient ? and poor ?, leading to ?
Miscarriages often caused by placental disorders (up to 40%)!
Cause: usually abnormal chromosomal content due to errors at fertilization, resulting in abnormal placental tissue or poor placenta development
Pre-eclampsia: Mother develops HTN. Can be caused by inefficient development of maternal blood vessels and poor invasion of the placenta into myometrium, leading to placental insufficiency. Baby will be small and fragile.
Another disorder of the placenta is Hydatidiform mole. What is this?
Molar pregnancies - complications inc ?, + requires ?
Hydatidiform mole, aka molar pregnancy: 2 types:
Complete molar: empty oocyte fertilised by 1 or 2 sperm; all genes from father. Abnormal, swollen placental tissue forms fluid-filled cysts. Also no foetal tissue formation
Partial/incomplete molar - father provides 2 sets of chromosomes. Embryo has 69 chroms, not 46
Occurs when 2 sperm fertilize egg
May be normal and abnormal placental tissue–> early miscarriage
A molar pregnancy can have serious complications, inc choriocancer, and requires early treatment
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Placental CRH and cortisol - Both increase from T2 onwards
Cortisol involved in Fetal lung maturity + Metabolic changes (insulin resistance)
CRH – possibly involved in labour initiation?
