2. Gastrulaton

Question 1

When does Gastrulation occur?

Answer 1

1. In the third week of development

Question 2

Briefly, what occurs during gastrulation?

Answer 2

1. Bilaminar disk –> Trilaminar disk
2. Consists of three germ layers:

• Ectoderm
• Mesoderm
• Endoderm

Question 3

In depth, how does gastrulation occur?

Answer 3

1. Primitive streak forms in the caudal (top bit) epiblast
2. Migration and invagination of epiblast cells
3. Displacement of hypoblast (lower layer) and creation of third layer
4. = ectoderm, mesoderm, endoderm

Question 4

There are two holes in which layer, and what is their purpose?

Answer 4

1. There are two holes in the MESODERM (one near the top, one near the bottom if you’re looking at the mesoderm from above or below)
2. They will become the future mouth and anus

Question 5

What layers form from the epiblast, the new layer and hypoblast respectively?

Answer 5

1. Ectoderm
2. Mesoderm
3. Endoderm

Question 6

What body ‘parts/systems’ are derived from each layer?

Answer 6

Question 7

What does a cross section of the embryo look like now it has three layers?

Answer 7