Session 1: Laura Mongan (incomplete)

Question 1

What is the embryonic period of development?

Answer 1

Weeks 3 to 8

Question 2

(Briefly) What happens during the embryonic period? What significance does this have?

Answer 2

1. All major structures and systems form - lots of cell division and differentiation
2. Period with greatest risk of major congenital malformation (teratogenesis) due to environmental exposure and drug therapy

Question 3

What are the key events that occur during weeks 3 and 4 of development? (4)

Answer 3

1. Gastrulation
2. Neurulation
3. Segmentation
4. Folding

Question 4

What is gastrulation? When and how does it occur?

Answer 4

Process of changing the bilaminar embryonic disk (epiblast + hypoblast) into a trilaminar disk - week 3

Primitive streak forms in the caudal epiblast, leading to migration and invagination of epiblast cells

Question 5

What (from bilaminar embryonic disk) differentiates into the three germ layers?

Answer 5

Epiblast

Question 6

What are the three germ layers?

Answer 6

1. Ectoderm
2. Mesoderm
3. Endoderm

Question 7

What does the ectoderm give rise to?

Answer 7

Organs and structures that maintain contact with outside world - nervous system, epidermis

Question 8

What does the mesoderm give rise to?

Answer 8

Supporting tissues - muscle, cartilage, bones, vascular system (heart and vessels)

Question 9

What does the endoderm give rise to?

Answer 9

Internal structures - epithelial lining of GI tract, respiratory tract; parenchyma of glands

Question 10

What is different at the regions of the future mouth and anus in the trilaminar disk?

Answer 10

There is no mesoderm - ectoderm and endoderm lie next to each other

Question 11

What is the significance of the node at the primitive streak?

Answer 11

Ciliated cells at the node result in left-ward flow of signalling molecules - side-specific cascades initiated

Question 12

What important structure gets formed by the end of gastrulation?

Answer 12

Notochord

Question 13

What is a notochord and what is its significance?

Answer 13

• Solid rod of cells running in the midline (bisects embryonic disk
• Important signalling role in directing differentiation of overlying ectoderm to neurectoderm

Question 14

What is neurulation?

Answer 14

Process of formation of neural tube - develops into the spinal cord and brain in the future

Question 15

Name the different layers formed during neurulation (5)

Answer 15

1. Paraxial mesoderm
2. Intermediate mesoderm
3. Somatic mesoderm
4. Splanchnic mesoderm (viscera)
5. Intraembryonic coelom