Embryology 2

Question 1

Where is the primitive streak formed?

Answer 1

Midline of the epiblast by invagination (dipping in of cells).

Question 2

What can form once the primitive streak has formed?

Answer 2

The axis of the embryo

Question 3

Where do the epiblast cells migrate to?

Answer 3

Between epiblast and hypoblast layers

Question 4

Name the three germ layers formed.

Answer 4

1. Ectoderm
2. Mesoderm
3. Endoderm

Question 5

What happens when the three germ layers have been formed?

Answer 5

Trilaminar disc is formed and become specialised.

Question 6

Describe the formation of the notochord.

Answer 6

The primitive streak is in the ectoderm layer
Cells sink down from primitive streak to form a sold tube
The solid tube of cells is called the notochord

Question 7

Describe the neural tube formation

Answer 7

The neural plate is in the ectoderm
Neural plate sinks down to from a neural tube
Notochord induces ectodermal cells in the midline to form a neural tube

Question 8

What is the process of neural tube formation called?

Answer 8

Neurulation

Question 9

What does the sonic the hedgehog gene do?

Answer 9

Carries instructions to make a protein called Sonic hedgehog

Question 10

What induces the mesoderm to thicken?

Answer 10

The neural tube

Question 11

Name the three parts that the mesoderm separates into.

Answer 11

Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm

Question 12

Which part of the mesoderm splits?

Answer 12

Lateral plate mesoderm

Question 13

What does segmentation of paraxial mesoderm form?

Answer 13

Somites

Question 14

Name the three parts which each somite divides into.

Answer 14

1. Dermatome
2. Myotome
3. Sclerotome

Question 15

What do dermatomes form?

Answer 15

Dermis of skin

Question 16

What does the myotome form?

Answer 16

Muscles

Question 17

What does the sclerotome form?

Answer 17

Bones including vertebrae.

Question 18

What day of the embryotic period does the heart start to beat?

Answer 18

Day 24

->maybe think of Christmas Eve?

Question 19

Which parts of the body develop from the neural tube during week 4-8?

Answer 19

Forebrain
Midbrain
Hindbrain
Spinal cord

Question 20

Where does the gut form from?

Answer 20

Endoderm during weeks 4-8

Question 21

Where does the urogenital system form from?

Answer 21

Intermediate mesoderm during weeks 4-8

Question 22

Where do body cavities form from?

Answer 22

Lateral plate mesoderm during weeks 4-8

Question 23

How many pairs of somites form during weeks 4-8?

Answer 23

43 pairs

Question 24

Where do the 43 pairs of somites form?

Answer 24

Paraxial mesoderm and then differentiate further

Question 25

What else happens during week 4-8?

Answer 25

Limb buds form
Neck development- pharyngeal arches