Embryology Lecture

Question 1

Where does fertilisation normally take place?

Answer 1

In the ampullary region of the fallopian tube

Question 2

What is embryonic age?

Answer 2

The time since fertilisation

Question 3

What is the germinal stage?

Answer 3

Time from fertilisation to end of second week

Question 4

What is the embryonic period?

Answer 4

The time from third week to end of eighth week

Question 5

What is the foetal period?

Answer 5

The time from ninth week to birth at 38 weeks

Question 6

What is the gestational age?

Answer 6

Time since last menstruation. Embryonic age age - 2 weeks

Question 7

By day 3 of development the cell has developed an outer and inner cell mass. What are they called?

Answer 7

Outer = trophoblast
Inner = blastocyst

Question 8

What does the primitive endoderm contain?

Answer 8

Yolk sac and gut endoderm

Question 9

What does the trophoblast (outer cell layer) contain?

Answer 9

Yolk sac and placenta

Question 10

What is the definition of trophoblast?

Answer 10

Food bud

Question 11

From what week are the nutrients provided by the mother’s blood?

Answer 11

Week 12 onwards

Question 12

Where is the normal implantation site for the blastocyst (inner cell layer)?

Answer 12

The upper part of the body of the uterus on the posterior wall

Question 13

What is a placenta previa and why might the mother need a caesarian section?

Answer 13

A placenta previa = placenta blocking the cervical opening

There would be extreme haemorrhage if delivered normally

Question 14

What week of development does the trophoblast differentiate into 2 layers? What are they called?

Answer 14

Week 2
Cytotrophoblast
Syncytiotrophoblast

Question 15

What are the 2 layers of the bilaminar embryonic disk called?

Answer 15

Epiblast

Hypoblast

Question 16

The hypoblast contributes to formation of 2 cavities - what are they?

Answer 16

Yolk sac

Chorionic cavity

Question 17

At the end of the 2nd week the epiblast (1 of the 2 layers of bilaminar disc) is disk shaped. In week 3 a feature appears on the epiblast - what is it called?

Answer 17

Primitive streak

Question 18

What is the bioethics of the primitive streak?

Answer 18

Appearance of the primitive streak is the appearance of a defined individual

Question 19

The bilaminar disk becomes a trilaminar disk - what are the 3 layers of this?

Answer 19

Ectoderm
Mesoderm
Endoderm

Question 20

What is the process of creation of the ectoderm, endoderm and mesoderm called?

Answer 20

Gastrulation

Question 21

What does the ectoderm create?

Answer 21

Organs and structure in contact with outside world

Question 22

What does the mesoderm create?

Answer 22

Supporting tissues eg muscle cartilage and the vascular system

Question 23

What does the endoderm create?

Answer 23

Internal structures

Question 24

When does gastrulation begin and what is it?

Answer 24

3rd week development - start of embryonic period (week 3-8)

Bilaminar disk converted to trilaminar disk - three germ layers (mesoderm, endoderm and ectoderm)

Question 25

What runs down the midline attaching to the node at the top of the primitive streak?

Answer 25

The notochord

Question 26

What does the notochord do?

Answer 26

Converts ectoderm to neurectoderm (beginning of CNS)

Question 27

What is the conversion of ectoderm to neurectoderm called?

Answer 27

Neurulation

Question 28

When do somites first appear?

Answer 28

At day 20

Question 29

Somites derive into 3 tissue types - what are they?

Answer 29

Dermatome (dermis)
Myotome (muscles)
Sclerotome (bones)

Question 30

What is the buccopharyngeal membrane?

Answer 30

Future mouth site

Question 31

At what development stage does implantation usually occur?

Answer 31

Blastocyst

Question 32

From which embryonic tissue are the 3 germ cell layers derived?

Answer 32

Epiblast

Question 33

What is the cloacal membrane?

Answer 33

Future anus

Question 34

What is an ectopic pregnancy?

Answer 34

When blastocyst is in the fallopian tube rather than uterus