Embryology

Question 1

2 divisions of trophoblast, at implantation

Answer 1

Synciotrophoblast: makes connection with epithelia

Cytotrophoblast: surrounds the blastocyst

Question 1

What happens when the capillaries are eroded by the synciotrophoblast?

Answer 1

The uroplacental circulation is established.

Question 2

What is the zygote called after the 8 cell stage when it starts moving towards the uterus?

Answer 2

Morula (morula stage)

Question 3

Bilaminar disk contents

Answer 3

Hypoblast (primary endoderm)
Epiblast (primary ectoderm)

Question 4

Amniotic cavity forms from _____

Answer 4

The epiblast

Question 5

The exocoelomic membrane forms from ____

Answer 5

The hypoblast

Question 6

What is the primary umbilical vesicle?

Answer 6

Hypoblast + Exocoelomic membrane.

= Yolk sac

Question 7

What is the extraembryonic mesoderm?

Answer 7

It is the layer that forms between the exocoelomic membrane and the trophoblast; its job is to detach the blastocyst from the trophoblast except at the connecting stalk.

Question 8

What is the extraembryonic coelum and what are its two divisions?

Answer 8

2 on the picture.

It is composed of:
- Extraembryonic splanchnic mesoderm (on the yolk sac)
- Extraembryonic somatic mesoderm (in contact with trophoblast)

Question 9

When does the primary umbilical cavity become the secondary umbilical cavity?

Answer 9

The the extraembryonic mesoderm forms and there is extraembryonic cavity

Question 10

The embryoblat is suspended to the chorion by the ________ into the extraceolomic cavity.

Answer 10

Connecting stalk.

Question 11

When is the fetomaternal circulation established?

Answer 11

When the primary chorionic villi are formed.

Question 12

From which embryoblastic layer does the endoderm originate?

Answer 12

EPIBLAST (migrating epiblastic cells replace hypoblastic cells, even though hypoblast is the primary endoderm). Epiblastic cells form all of the layers

Question 13

Name the 2 zones where ectoderm & endoderm remain fused during grastrulation

Answer 13

Cloacal membrane: urogenital tract

Prechordal plate: oropharyngeal membrane

Question 14

The prechordal plate induces ….

Answer 14

The notochord. Prechordal plate is a signalling center.

Question 15

Which structure’s failure to close leads to a sacrococcygeal teratoma?

Answer 15

Primitive streak

Question 16

Notochord main roles

Answer 16

Induced by prechordal plate:

Chord (solid structure), growing central to the trilaminar disk. Will:
- Induce neural plate (leading to neurulation, for CNS creation)
- Signal for axial MSK system (para-axial mesoderm)
- Define primordial longitudinal axis of the embryo

Question 17

Where does the cardiogenic area form?

Answer 17

On top of the prechordal plate

Question 18

What does the embryonic ectoderm give rise to?

Answer 18

CNS and PNS, inner ears, eyes, neural crest and many CT of the head.

Question 19

What does the intraembryonic mesoderm give rise to?

Answer 19

Pluripotent cells.
Skeletal muscles and CT, blood cells, lining of blood vessels, viscera’s smooth muscles

Question 20

What does the embryonic endoderm give rise to?

Answer 20

Epithelial linings of respiratory and digestive tracts, including associated glands

Question 21

What does the paraxial mesoderm give rise to?

Answer 21

Somites: 31 segments, from which axial skeleton and muscles arise

Question 22

What does the intermediate mesoderm give rise to?

Answer 22

Urogenital system

Question 23

What does the lateral mesoderm give rise to?

Answer 23

Lateral mesoderm + ectoderm = intraembryonic somatic mesoderm (anterior body wall)

Lateral mesoderm + endoderm = intraembryonic splanchnic mesoderm (digestive tube wall)

Question 24

What does anterior neuropore misclosure lead to?

Answer 24

Acencephaly

Question 25

What does posteror neuropore misclosure lead to?

Answer 25

Spina bifida

Question 26

What does the neural plate give rise to?

Answer 26

Neural crest cells: ganglia, neurons