Gastrulation in mammals and chick

Question 1

What is formed during gastrulation?

Answer 1

Gastrula

Question 2

What does gastrulation specify?

Answer 2

Anterior posterior axis
Three germ layers

Question 3

How many layers does the pre-gastrulation embryo consist of?

Answer 3

2

Question 4

What are the two pre-gastrulation embryonic layers?

Answer 4

Epiblast and the hypoblast

Question 5

Why is the pre-gastrulation embryo a bilaminar structure?

Answer 5

It has two layers

Question 6

Epiblast other name?

Answer 6

ICM

Question 7

What lines the ICM?

Answer 7

Primitive endoderm

Question 8

Hypoblast other name?

Answer 8

Primitive endoderm

Question 9

What does gastrulation involve?

Answer 9

Cell migration and movement
Changes in cell cell interactions (adhesion)
Cross talk between cells (signalling pathways)

Question 10

Why do cell adhesions change during gastrulation?

Answer 10

Cells need to move, migrate and occupy new positions

Question 11

What is epiboly?

Answer 11

Cells flattening along their apico-basal axis

Question 12

What do bh epiboly and convergent extension cause/

Answer 12

Cells increase their SA

Question 13

What is convergent extension?

Answer 13

when a multilayered sheet of cells become narrower as cells make new contacts.

Question 14

What is invagination?

Answer 14

folding of an area of the exterior sheet of cells towards the inside.

Question 15

Effect of invagination on the apical and basal side?

Answer 15

Apical side becomes narrower
Basal side becomes broader

Question 16

What is the apical side of a cell?

Answer 16

The side facing towards the lumen, and away from the basement membrane

Question 17

What is ingression?

Answer 17

Cells detach bc they lose their cell-cell contacts, and migrate into the interior of the embryo

Question 18

WHat is involution?

Answer 18

The epithelium turns around on itself and spreads in the direction opposite to its basal margin.

Question 19

Why is the blastocoel cavity lost just before implantation?

Answer 19

The epiblast moves into where it was

Question 20

What is the embryonic visceral endoderm?

Answer 20

Visceral endoderm cells overlaying the epiblast
Lines the viscera of the body

Question 21

What happens to the epiblast between 5 and 5.25 days?

Answer 21

A combination of cell death and cell survival signals

Question 22

What do the cells lining the visceral endoderm produce?

Answer 22

BMP4

Question 23

What does BMP4 promote after being produces by the cells lining the visceral endoderm?

Answer 23

Cell death

Question 24

Effect of cells lining the visceral endoderm producing BMP4?

Answer 24

CElls on the inside will die bc they arent attached to a basement membrane

Question 25

Why do epiblast cells closest to the visceral endoderm not die?

Answer 25

They have a basement membrane between the visceral endoderm and the cells of the epiblast

Question 26

What is the consequence of the cells in the centre of the epiblast dying and the ones lining it living?

Answer 26

There is a cavity in the middle of the embryo, and the embryo becomes cup shaped

Question 27

What happens to the junction between the extraembryonic visceral endoderm and the embryonic visceral endoderm as a result of the cavity forming?

Answer 27

A thickening

Question 28

What is the thickening between the extraembryonic visceral endoderm and the embryonic visceral endoderm responsible for?

Answer 28

Start of gastrulation