Embryology 2

Question 1

What cells make the trophoblast

Answer 1

• Cytotrophoblast

- Syncytiotrophoblast

Question 2

What do cytotrophoblast & syncytiotrophoblast help the trophoblast with

Answer 2

Implantation

Question 3

What cells make the embryoblast

Answer 3

• Hypoblast

- Epiblast

Question 4

Why doesn’t the mother’s immune system attack the blastocyst

Answer 4

• Syncytiotrophoblast release substances which hide it from IS
• Multinucleated cells formed
• No gaps for immune cells to get to embryo

Question 5

What is the first stage of organisation of the body plan

Answer 5

Bilaminar formation

Question 6

What is the significance of the bilaminar

Answer 6

• Bilinear

- Established dorsal & ventral axis

Question 7

Why bilinear

Answer 7

Two embryoblast cells

Question 8

Which cells form the ventral aspect of embryo

Answer 8

Hypoblasts

Question 9

Which cells form the dorsal aspect of embryo

Answer 9

Epiblasts

Question 10

How does amniotic cavity form

Answer 10

Small fluid-filled cavity in epiblasts

Question 11

When does full implantation take place

Answer 11

Day 9

Question 12

What happens in full implantation

Answer 12

• Migration of hypoblast cells encase blastocyst cavity

- Primary yolk sac forms

Question 13

When does the coagulation plug form

Answer 13

Full implantation

Question 14

What is the function of the coagulation plug

Answer 14

Protect blastocyst on uterine lining

Question 15

How does embryoblast receive nutrients if no placental circulation happening yet

Answer 15

Diffusion of nutrients via uterine gland

Question 16

How is the uteroplacental circulation established

Answer 16

Syncytiotrophoblast erodes walls of maternal capillaries

Question 17

Where do the different cells receive their nutrients from

Answer 17

Trophoblastic lacuna

Question 18

What is the extraembryonic mesoderm

Answer 18

Layer of connective tissue derived from yolk sac cells

Question 19

When is extraembryonic mesoderm formed

Answer 19

Simultaneously with uteroplacental circulation

Days 10-11

Question 20

Where is extraembryonic mesoderm formed

Answer 20

Between 1ry yolk sac & cytotrophoblast

Question 21

When extraembryonic mesoderm is fully developed what does it cover

Answer 21

Amniotic cavity

Question 22

When does blastocyst receive blood supply

Answer 22

When trophoblast breaks down the capillary wall

Question 23

What forms and grows in the extraembryonic mesoderm

Answer 23

Chrionic cavity

Question 24

When does chrionic cavity form

Answer 24

Days 12-13

Question 25

When is 2ry (definitive) yolk sac formed

Answer 25

Days 12-13

Question 26

How is the 2ry yolk sac formed

Answer 26

2nd wave of hypoblast cells migrating

Question 27

Where are the amniotic cavity & 2ry yolk sac suspended

Answer 27

Chronic cavity by connecting stalk

Question 28

What forms the bilamina disc

Answer 28

Embryonic sac & definitive yolk sac

Question 29

What is the fate of the connecting stalk

Answer 29

Forms umbilical cord

Question 30

What hormones do syncytiotrophoblast secrete What is its function What is it helpful for

Answer 30

Human chronic gonadotrophin - hCG - Maintains endometrium - Role in maternal immunotolerence Pregnancy testing

Question 31

How frequent is abnormal implantation sites

Answer 31

- 2% of pregnancies | - 9% of pregnancy-related deaths

Question 32

What is placenta Previn

Answer 32

When placenta block vagina

Question 33

What can placenta Persia cause

Answer 33

Severe bleeding in late pregnancy

Question 34

Where do the majority of ectopic pregnancies happen

Answer 34

Uterine tube

Question 35

How can abdominal implantation happen

Answer 35

Zygote entering the gap between ovary & uterine tube

Question 36

When does lithopaedion occur

Answer 36

When abdominal pregnancy remains undiagnosed

Question 37

How does baby die in lithopaedion

Answer 37

Too large to be reabsorbed —> calcifies

Question 38

Why does foetus calcify in lithopaedion

Answer 38

Protect mother from its necrotic tissue

Question 39

What is the hydatidiform mole

Answer 39

Development of trophoblast without embryonic tissue

Question 40

What causes hydatidiform mole

Answer 40

Fertilisation of an empty egg

Question 41

Explain parental imprinting in relation to hydatidiform mole

Answer 41

Parental genes favour formation of trophoblast at the expense of embryo

Question 42

Why does hydatidiform mole still make you think someone is pregnant

Answer 42

Syncytiotrophoblast produces hCG —> +ve pregnancy test