9. Vertebrate Gastrulation I

Question 1

What is gastrulation according to Lewis Wolpert?

Answer 1

The most important event in your life

Gastrulation is crucial for the development of multicellular organisms.

Question 2

What is the strict definition of gastrulation?

Answer 2

Formation of the gut through internalization of epithelial sheet

Question 3

What is the broader definition of gastrulation?

Answer 3

Process leading to formation of three germ layers

Question 4

What does the ectoderm give rise to?

Answer 4

Skin, sense organs, nervous system

Question 5

What structures are formed from the mesoderm?

Answer 5

Skeleton, circulatory system, muscles, excretory system, most of reproductive system

Question 6

What does the endoderm develop into?

Answer 6

Digestive and respiratory tracts and associated structures

Question 7

What is invagination in gastrulation?

Answer 7

Inward movement/in-pocketing of epithelial sheet

Question 8

What drives invagination?

Answer 8

Apical constriction (contraction of apical actin-myosin meshwork)

Question 9

What is involution?

Answer 9

Collective cell migration led by ‘leader cells’ creating a second epithelial sheet inside embryo

Question 10

What is delamination?

Answer 10

Duplication of epithelial sheet to create another layer

Question 11

What is ingression?

Answer 11

Cells lose epithelial phenotype and become invasive

Question 12

What transition is involved in ingression?

Answer 12

Epithelial-to-mesenchymal transition (EMT)

Question 13

What is epiboly?

Answer 13

Spreading movement to cover embryo

Question 14

What drives epiboly?

Answer 14

Cell division, intercalation, changes in cell size/shape

Question 15

What happens during initial polarity and axis formation in frog gastrulation?

Answer 15

Egg has animal-vegetal polarity; sperm entry triggers cortical rotation

Question 16

What is the ‘grey crescent’?

Answer 16

Future dorsal lip of blastopore formed after cortical rotation

Question 17

What is the blastula stage?

Answer 17

Stage with multiple cell divisions creating a fluid-filled cavity (blastocoel)

Question 18

What defines the animal and vegetal poles in the blastula?

Answer 18

Animal pole has smaller cells; vegetal pole has larger cells due to yolk content

Question 19

What initiates early gastrulation in frogs?

Answer 19

Begins at dorsal lip of blastopore with bottle cells undergoing apical constriction

Question 20

What occurs during mid gastrulation?

Answer 20

Involution continues; cells migrate under blastocoel roof

Question 21

What is formed during late gastrulation?

Answer 21

Three germ layers fully formed; notochord forms in dorsal mesoderm

Question 22

When does human gastrulation occur?

Answer 22

During the second week of gestation

Question 23

What structures are involved in human gastrulation?

Answer 23

Epiblast and hypoblast

Question 24

What forms the primitive streak in human gastrulation?

Answer 24

Equivalent to dorsal lip in frog

Question 25

What is formed by invagination in human gastrulation?

Answer 25

Endoderm (replaces hypoblast)

Question 26

What does ingression form in humans?

Answer 26

Mesoderm through EMT

Question 27

What does the remaining epiblast become?

Answer 27

Ectoderm

Question 28

What are the key functions of gastrulation?

Answer 28

Establishes three germ layers, creates body axes, forms notochord

Question 29

What is the blastocoel?

Answer 29

Cavity that facilitates movements and separates germ layers

Question 30

What is the blastopore?

Answer 30

Opening where cells internalize (becomes anus)

Question 31

What is the archenteron?

Answer 31

Primitive gut cavity

Question 32

What is the notochord?

Answer 32

Mesodermal structure that induces neural plate

Question 33

What is the primitive streak?

Answer 33

Site of cell movements in human embryo

Question 34

True or False: Gastrulation links to subsequent stages such as neural induction.

Answer 34

True