placenta embryology

Question 1

purpose of the placenta ?

4

Answer 1

1) protection from microorganisms reaching the foetus
2) Nutrition from maternal circulation
3) Exchange of O2,CO2 = respiratory
4) Excretion , removal of waste products from the kidney
5) progesterone and oestrogen production taken over from corpus luteum

Question 2

what is decidua reaction

decidua = mothers membrane

Answer 2

1) trophoblast binds to endometrium causing the Decidua reaction
after implantation = the endometrium is called the decidua
it has 3 parts :
1) decidua basalis
2) decidua capsular
3) decidua parietals
2+3 fuse at week 14-16 –> decidua Vera
2) Progesterone = increased vascular swelling + glycogen granules for nourishment, capillaries form

Question 3

development of the placenta

Answer 3

Day 7 : implantation via integrin
day 8 :development, the trophoblast cells differentiate into the outer multinucleated syncytiotrophoblast ( produces Human Chorionic Gonadotropin) and cytotrophoblasts
Day 9 : yolk sac + Extraembryonic mesoderm
Day 12 : extraembryonic mesoderm surrounds the yolk sac ( splanchnic ), and Amniotic cavity (somatic mesoderm)

Question 4

what is the role of the multinucleated syncytiotrophoblast?

Answer 4

1) bring nutrients
2) produce Human Chorionic Gonadotropin (hCG)
3) makes blood lakes to provide nutrients

Question 5

What happens in week 3 ? development of the chorionic cavity ?

Answer 5

1) Primary villi = cytotrophoblasts in centre surrounded by synctiotrophoblast
2) Secondary villus = mesoderm core develops in the centre , then cytotrophoblasts+ synctiotrophoblast on outside
3) Tertiary villus = blood vessels of fetus in mesoderm

Question 6

what has happened by week 5 ?

3

Answer 6

• tertiary vilii form
• cytrotrophoblast now encompass the synctiotrophoblast = cytotrophoblastic shell
• Umbilical cord development

Question 7

what is the purpose of the amniotic sac

Answer 7

1) 1L of fluid
2) gives baby shape and definition
3) The baby is moving against resistance hence develops muscle
4)amniotic fluid = hydrates the skin, lungs , GI tract
5)

Question 8

Outline the Feto-Maternal exchange

Answer 8

1) cytotrophoblast = external by the end, they invade into the spiral arteries, making hybrid blood vessels
2) Maternal blood= pools into the intervillious spaces
3) Nutrients –> Chorionic Villi ( fetal capillaries )

Question 9

Umbilical cord components

Answer 9

2 arteries= umbilical arteries ( waste, low in nutrients, deoxygenated )
1 Vein = oxygenated
Warttons jelly contracts and closes these vessels after birth

Question 10

Decidual ( motherly ) components

Answer 10

1) Decidua basalis = embryonic pole = placenta
2) Decidau capsularis = opposite the decidua basalis
3) Decidua Parietalis = not associated with the embryo