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Embryology, Pregnancy & Birth > Placenta #1 > Flashcards

Placenta #1 Flashcards

1
Q

Why is the placenta a dualistic organ?

A

Derived from mother & foetus

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2
Q

What does the foetal part of the placenta develop from?

A

Chorion fondosum

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3
Q

What does the maternal part of the placenta develop from?

A

Decidua basalis

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4
Q

How does the placenta connect to embryo?

A

-Placenta connects to the conceptus via the umbilical cord
-Conceptus = all structures that develop from zygote

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5
Q

What is the endocrine role of the placenta?

A

Secretes oestrogens and progesterone to maintain pregnancy

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6
Q

Shape of placenta?

A

Flattened discoid organ

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7
Q

What is the foetal surface of the placenta covered in?

A

-Amnion (innermost membrane enclosing embryo)
-Umbilical cord inserted

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8
Q

What is found on the maternal surface of the placenta?

A

-Attaches to decidua basalis
–> which is formed by 15-20 cotyledons
-Cotyledons = transmit foetal blood & allow exchange of O2 & nutrients with maternal blood - are formed by interaction of patches of allantochorion with endometrium

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9
Q

Chorion vs amnion?

A

-Amnion = innermost membrane enclosing embryo
-Chorion = outermost membrane enclosing embryo

A before C!

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10
Q

What is the chorioamnion?

A

-Membranes surrounding the embryo
-Made up of:
*Amnion = innermost
*Chorion = outermost

A before C!

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11
Q

How is the chorioamnion formed?

A

Basal & chorionic plates meet @ edges to form chorioamnion membranes

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12
Q

Where is amniotic fluid found?

A

Within the amniotic membrane that surrounds the embryo

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13
Q

Describe the amnion.

A

-Translucent CT base
-Non-ciliated epithelial cells

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14
Q

What is the chorion (where foetal part of placenta develops from) developed from?

A

From trophoblast layer of blastocyst

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15
Q

Describe how the embryonic placenta forms.

A

Embryonic placenta develops from proliferation of syncytiotrophoblast & cytotrophoblast cells & extraembryonic layer of mesoderm cells

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16
Q

What is important to do following delivery of the placenta - in terms of membranes?

A

Check both the chorion & amnion are present

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17
Q

What is important to do following delivery of the placenta - in terms of membranes?

A

Check both the chorion & amnion are present
–> absence of one = linked to congenital abnormalities

18
Q

How does the umbilical cord/funis develop?

A

-Extends from foetal surface of placenta (chorion fondosum) to umbilical areas of foetus
-Originates from duct between amniotic sac & yolk sac

19
Q

What vessels are found within the umbilical cord?

A

x2 umbilical arteries
–> these spiral around:
x1 umbilical vein (in Wharton’s jelly = mucoid CT)

20
Q

What does this histological image show?

A

Cross-section of umbilical cord
-x2 umbilical arteries
-x1 umbilical vein
-Wharton’s jelly
-Epithelial surface

21
Q

Where does placenta formation begin here?

A

Partially implanted early bilaminar blastocyst (6 days)

22
Q

Outline the basics of what implantation is & what cellular components make up the blastocyst during this.

A

Implantation = blastocyst is implanted into uterine endometrium
-Inner cell mass = embryoblast -> becomes embryo
-Outer cell mass = trophoblast -> becomes placenta & membranes (chorion)

23
Q

What changes occur to the trophoblast during implantation?

A

Trophoblast proliferates forming x2 layers
-Syncytiotrophoblast (outer)
-Cytotrophoblast (inner)

24
Q

What day does placentation begin?

A

Day 7

25
Q

Describe placenta formation.

A

-Trophoblast -> outer layer of cells enveloping blastocyst
-Trophoblast makes contact with maternal endometrium (the decidua basalis) to form maternal portion of placenta

Prelacunar
As blastocyst makes contact with decidua basalis = PLACENTATION BEGINS!!!
-Maternal placenta develops from decidua basalis (deepest layer of endometrium – lining of uterus)

-X3 cell types – derived from trophoblast:
*Villous cytotrophoblast cells - germinative (contains stem cells) population - proliferates throughout pregnancy & fuses to generate the syncytiotrophoblast (along with chorionic villi & placenta)
*Syncytiotrophoblast - forms epithelial covering of villous tree & is main endocrine component of placenta
*Extravillous trophoblast cells - non-proliferative & invade the maternal endometrium

-Embryonic placenta develops from chorion fondosum
–> Basal & chorionic plates meet @ edges to form chorioamnion -> amniotic membrane/amnion = envelopes embryo & the chorionic membrane/chorion = surrounds amnion

-Amnion = innermost membrane surrounding embryo (with amniotic fluid within)
-Chorion = outermost membrane surrounding amnion

-Chorionic membrane forms chorionic villi -> burrow into endometrium = makes up foetal portion of placenta

Lacunar
Lacunae from - these will become the intervillous spaces (filled with maternal blood = basal plate/maternal side of placenta)

26
Q

Chorionic & basal plate meaning?

A

-Chorionic plate = embryonic surface
-Basal plate = maternal surface

27
Q

Describe the structure of the basal plate (maternal surface of placenta).

A

-Perforated by spiral branches of uterine vessels

28
Q

What is found in the chorionic plate (embryonic side of placenta)?

A

-Primitive mesenchymal tissue containing branches of umbilical vessels
-Layer of cytotrophoblast & syncytiotrophoblast
-Stem villi connected to chorionic plate

29
Q

What is found in the basal plate (maternal side of placenta)?

A

-Part of layer of decidua basalis
-Degeneration of the outer syncytiotrophoblast at the cytotrophoblast shell & decidua junction
-Cytotrophoblast shell
-Syncytiotrophoblast

30
Q

What layer of the blastocyst forms a large part of the placenta & provides nutrients to the developing embryo?

A

Trophoblast

31
Q

What are the 2 layers of the trophoblast (outer layer of blastocyst)?

A

During most of foetal gestation -> trophoblast = made of x2 layers
1. Cytotrophoblast = in contact w/ endothelium of foetal capillaries
2. Syncytiotrophoblast = outer layer – in direct contact w/ maternal blood
-As gestation progresses -> cytotrophoblast atrophies – so at full term is only single layer of cells separating maternal blood & foetal capillary endothelium

32
Q

What are placental/chorionic villi?

A

Found on chorion of placenta & contain foetal blood vs (branches of umbilical arteries [x2] + branches of umbilical vein [x1])

33
Q

What are the intervillous spaces?

A

Spaces between chorionic villi - contains maternal blood (spiral arteries - which are branches of uterine arteries) flows into - on the basal plate of the placenta

34
Q

Describe maternal-placenta circulation.

A

*Uterine arteries with oxygenated blood branch into spiral (endometrial) arteries which perforate the basal plate (maternal surface) into the intervillous spaces of the placenta -> so uterine carry blood into placenta then spiral/endo carry to intervillous space
*Endometrial veins with deoxygenated blood branch into uterine veins -> so endo carry blood out of intervillous space to uterine veins

35
Q

What does the septum of the placenta contain?

A

-Decidual elements - covered by trophoblast cells

36
Q

What are cotyledons?

A

Areas between septa - on basal plate/maternal surface of placenta

37
Q

What is a test in pregnancy that can take blood sample from placenta?

A

CVS - Chorionic villus sampling

38
Q

Where is the foetal blood supply & maternal blood supply found?

A

-Foetal = in the chorionic villi
-Maternal = in chorionic spaces (by perforating basal plate)

39
Q

What are the different types of chorionic villi?

A
40
Q

What are some examples of (umbilical) cord conditions & what can happen?

A

-Short cord - traction & premature separation leading to insufficiency- abruption

-Long cord - cord around neck, cord prolapse, true knot

-Hyper & hypo-coiled cord – intrauterine growth restriction, foetal demise, associated with hypertensive disorders, placental abruption, maternal diabetes, polyhydramnios

-Anomalous insertions - marginal/Battledore, velamentous bifurcate – retained placenta, vasa previa, foetal blood loss - anaemia

-Vasa previa (can cause severe flood loss from foetus - as unprotected blood vs from umbilical cord travel across opening of cervix) – anaemia, foetal demise

41
Q

Placenta conditions resulting from incorrect location?

A

-Incorrect implantation = early miscarriage

-Abnormal trophoblast invasion – placenta accreta, preeclampsia, infarctions, abruption, pre-eclampsia,

-Low lying placenta & placenta previa (placenta completely/partially covers cervix) – lower segment caesarean section, short cord- traction & premature separation leading to insufficiency- abruption

-Bi lobed/Succenturiate lobe – vasa previa, post-partum haemorrhage and infection

Embryology, Pregnancy & Birth (9 decks)

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