Fetal membranes and placenta

Question 1

What is the role of the placenta?

Answer 1

Act as respiratory organ for foetus and the nutritive support from maternal circulation, excretion of waste and endocrine ( placenta takes over p/o from corp.l)

Question 2

Immune effects of the placenta?

Answer 2

Protects from microorganisms from crossing blood/placenta barrier- norovirus, mumps, rubella syphillis etc

Question 3

What is the decidua?

Answer 3

CT reaction of endometrium after implantation, prepares decidua (main maternal placenta component)

Question 4

How does decidua reaction take place?

Answer 4

Progesterone induced- inc. vascular swelling of stromal cells, accumulation of glycogen (nourishment for early embryo), prog. sprouting and ingrowth of caps.

Question 5

Decidua reaction days 7 + 8

Answer 5

Implantatino begins via integrin connections and HB-EGF

8. amniotic sac starts to form

Question 6

decidua reactions days 9 + 12

Answer 6

yolk sac starts to form and extraembryonic mesoderm begins to develop
12. EE mesoderms surrounds amniotic yolk and sac
yolk- EE splanchnic mesoderm
sac- EE somatic mesoderm

Question 7

Day 12 of decidua reaction

Answer 7

Trophoblastic lacunae form syncitotropoblasts (primitive fetal vessels)
Maternal sinusoids encapsulated within syncitiotrophoblast layer (embryo w nutrients)
Extraembryonic coelom starts to appear > chorionic cavity (day 13- 16)w

Question 8

What are the roles of syncitiotrophoblasts and cytotrophoblasts?

Answer 8

SCTB- invasive cells which get embryo to nutrient supply, target endometrium to break open sinusoids > trophoblastic lacunae
CTB- supply of syncitiotrophoblasts and produce villi in placenta

Question 9

What is the significance of the trophoblastic lacunae filling with blood?

Answer 9

Become villi of placenta ( foeto-maternal boundary), primary v fill with mesoderm and become sec. chorionic villi

Question 10

What are the differences between 1, 2 and 3 villi?

Answer 10

1. Cytotrophoblasts
2. Infiltrating extrambryonic mesoderm fills internal cavity
3. Mesoderm differentiates to form small blood vessels and fetal blood

Question 11

What should be done by week 3?

Answer 11

Connection between f and m vessels initiated
CTB start to proliferate around SCTB in collars
Chorionic cavity surround fetal tissues, connected by extraembryonic mesoderm connecting stalk

Question 12

What should be done by week 5?

Answer 12

Tertiary villi formed
CTB have encompassed SCTB, cytotrophoblast shell
Connecting stalk mesoderm develop fetal capillaries, primitive umbilical cord

Question 13

Feto-maternal exchange

Answer 13

CT invade endometrial spiral arteries (hybrid BV created)
Maternal blood pool in intervillous spaces (coated by SCTB), nutrients diffuse/ AT’erred into chorionic villi containing fetal capillaries and lead into vessels of C.stalk and to developing foetus.

Question 14

How are villi formed?

Answer 14

Stem vs branch villi- start off w several layers of barrier tissue, reduced to 2 partial layers and allows for close connections of M+F blood

Question 15

What are the 3 decidual layers formed?

Answer 15

D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo

Question 15

What are the 3 layers formed from endometrium in decidual reaction?

Answer 15

D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo

Question 15

What are the 3 decidual layers formed?

Answer 15

D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo

Question 15

What are the 3 decidual layers formed?

Answer 15

D. Basalis- embryonic pole > placenta ( paired with chorion frondosum- remember chorion foetal contb. DB and CF maternal)
D. Capsularis- opposite DB, caps site of implantation
D. Parientalis- all other endometrial surface not directly associated with embryo

Question 16

How is amnion formed?

Answer 16

Decidua P+C fuse w. amniochorionic membrane by end of tri. 3

Question 17

What is the role of amniotic fluid?

Answer 17

Made of water and fetal cellular debris- hydrates skin lungs and GI tract (swallowing), fluid comes from maternal cells and amnioblasts
Late gestation when urinary tract active, excretion into A.F

Question 18

How do maternal spiral arteries function?

Answer 18

Spurt into intravillous space, bathe into branching villus which has large SA and can take up nutrients/ exchange gas quickly

Question 19

Placental circulation and HDN

Answer 19

Rh+ blood of foetus mixing with Rh- mother- maternal immune system detects as foreign and RBC destruction
More a problem in 2nd pregnancy after AB produced from first exposure (parturition)

Question 20

Placental endocrine function

Answer 20

Programmes maternal metabolism to ensure it meets foetal demands- HGC, progesterone, oestrogen, placental parathyroid hormone, relaxin, CRH, chorionic somatommatrophin

Question 21

Role of 2 umblical arteries and 1 umbilical vein

Answer 21

Return deoxygenated blood with waste from foetus to placenta

Veins return oxygenated, nutrient rich blood from placenta to foetus- vessels are in Wharton’s jelly

Question 22

Umbilical abnormalities

Answer 22

Single umbilical artery ( common w genetic conditions), Entanglement, compression or prolapse

Question 23

Placental abnormalities

Answer 23

Shape, placenta previa, pre-eclampsia, abnormal implantation, trophoblastic disease (tumours)
PP- Blocks normal vaginal delivery, C section
Pre- eclampsia- HT and proteinuria- CTB in spiral arteries don’t invade properly- eclampsia, renal failure, PO

Question 24

Implantation abnormalities

Answer 24

Morbidly adherent placenta, doesn’t fully detatch at parturition and severe haemorrhage/ damage to uterus
Accreta- too deep in endometrium (mm)
Increta- into myommetrium
Percretia- through perimetrium

Question 25

Molar pregnancies (gestational trophoblastic disease)

Answer 25

Non cancerous- complete, egg w no maternal DNA or partial (triploid gestations)
Cancerous- invasive, arise if benign moles progress