L52. Embryology

Question 1

What is a fertilised ovum called?

Answer 1

Zygote

Question 2

After what period of time is a zygote formed?

Answer 2

24h

Question 3

What is the mass of cells formed from 4-6 days called?

Answer 3

Morula

Question 4

What is the hollow ball of cells formed from 6-10 days called?

Answer 4

Blastocyst

Question 5

What are the components of a blastocyst?

Answer 5

Outer layer of cells (trophoblast) and an inner cell mass.

Question 6

At 10 days, what does the trophoblast contain?

Answer 6

2 layered-embryo

Question 7

Name the 2 layers of the 2 layered embryo.

Answer 7

Epiblast (inner layer)

Hypoblast (outer layer)

Question 8

What do the epiblast and hypoblast do?

Answer 8

Epiblast gives rise to the embryonic ectoderm, mesoderm and endoderm.
Hypoblast helps form the endoderm.

Question 9

How many placentas are present in identical twins?

Answer 9

1 placenta

Question 10

How many placentas are present in fraternal twins?

Answer 10

2 placentas

Question 11

What is the groove called which forms during development?

Answer 11

The primitive streak

Question 12

Where are mesodermal cells found?

Answer 12

Between the epiblast and the hypoblast

Question 13

What do mesodermal cells do?

Answer 13

Push through the primitive streak and spread out to form the 3rd layer

Question 14

What is organogenesis?

Answer 14

When organs (including CNS) develop between weeks 3-8

Question 15

Describe the flow chart of how the neural tube develops.

Answer 15

Neural fold -> neural groove -> neural tube

Question 16

What is the condition called when the neural tube persists?

Answer 16

Spina bifida

Question 17

What happens around 25 days old?

Answer 17

Front and back ends of the embryo fold in the middle (folds around yolk sac) and heart, liver and lungs appear.

Question 18

Name the 3 embryonic layers and their positions.

Answer 18

Ectoderm (outer covering)
Mesoderm (middle)
Endoderm (inner lining)

Question 19

What is the ectoderm involved in producing?

Answer 19

Skin, oral mucous membranes, CNS, enamel

Question 20

What is the mesoderm involved in producing?

Answer 20

Connective tissue, blood vessels, reproductive system

Question 21

What is the endoderm involved in producing?

Answer 21

Respiratory system, alimentary (pharynx to anus)

Question 22

What is the ectomesenchyme?

Answer 22

A “4th layer” which develops the peripheral nervous system (sensory and autonomic nerves) and oral structures (except enamel)