Gastrulstion And Neurulation

Question 1

Name each part

Answer 1

Question 2

how does the endoderm form?

FIRST STEP OF GASTRULATION

Answer 2

at the begining of week 3, a node will form on the epiblast layer. (this is known as the primitive streak)
the epiblast cells will divide and flood through this node into the embryo and replace some of the hypoblasts.
This is forming the endoderm.

Question 3

how is the mesoderm formed?

SECOND STEP OF GASTRULATION

Answer 3

mesoderm forms as the epiblasts spread between the outer most layer of epiblasts and now the inner most layer of epiblasts that have now made the endoderm.

Question 4

what is the notochord?

Answer 4

it provides both mechanical and signalling cues in the developing embryo.
it will organise the dorsal structures like the spine/ nervous system

Question 5

what will the notochord release and why?

Answer 5

the notochord will release chordin, noggin and follistatin.
this is so that it blacks BMP in order to get the develoment of the NS.

Question 6

what are BMP and what do they do?

Answer 6

they are bone morphogenic proteins . this will drive formation of the skin on the back, but the notochord wants to drive neural tissue instead first.

Question 7

what kind of epithelia will be founf in neuroectoderm?

Answer 7

columnar epithelium

in neural plate

Question 8

what will the notocord induce?

Answer 8

neurulation

Question 9

what days will nurulation take place?

Answer 9

20-21

Question 10

what happens in the first stages on neurulation?

Answer 10

the neural plate (which forms the notocord) converts to a groove then a tube. the cells on the neural plate will thicken forming the folds and a groove.

Question 11

what happens on day 25/27?

Answer 11

there will be closure at both end of the neural tube

Question 11

second stage on neurulation?

Answer 11

the folds will fuse to make a tunnel
the neural tube is now formed.

this happens on day 22

Question 12

2 failures of the neural tube closure?

Answer 12

1- spina bifida
2- anencephaly (you dont get full brain development)

Question 13

what is the nueral crest?

Answer 13

these are specialised cells that migrate away from the neural tube epithelium

Question 14

what do neural crest cells do?

Answer 14

they derive from the edges of the neural tube and undergo an epithelial to mesenchymal transition to become mobile and migarate away from the neural tube to widespread destinations.

Question 15

what are defects in neural crest development?

Answer 15

pigment anomilies, deafness, GI motility issues.

Question 16

how will mesoderm form in gastrulation?

Answer 16

the epiblast cells will burrow inbetween the epiblast and hypolast to form notocord and the mesoderm.

Question 17

summary fomration of 3 germ layers.

Answer 17

• cells from the epiblast flow into primative streak
• these cells replace the hypoblast cells to form endoderm
• cells lie between the hypoblast and epiblast form mesoderm
• cells that remain in the epiblast become ectoderm

Question 18

what are the 3 types of mesoderm

Answer 18

• paraxial mesoderm
• intermediate mesoderm
• lateral plate mesoderm

Question 19

what does paraxial mesoderm become

Answer 19

segmented to form somites

Question 20

how are somites formed?

Answer 20

they are fomed on the notch clock cycle
- they have an internal timer defined by 90 mins
- a wave of FGF signal passes along the embryo in a rostral caudal direction
- when then FGF wave passes cells, they are programed to change into part of a somite according to where they are in the clock cycle.

Question 21

what determines wether it is the front or tail end of the somite segemnt that forms?

Answer 21

if the wave passes early in the clock cycle= becomes the front end of that segment
if the wave passes late in the cycle = tail end

Question 22

homeobox genes function

Answer 22

they direct the formation of body structures at the right place along the body.

Question 23

derivates of paraxial mesoderm

Answer 23

head and somites
- skelerotome
- Myotome
- Dermatome

Question 24

derivates of intermediate mesoderm

Answer 24

-kidneys
- urogenital strctures

Question 25

derivates of lateral plate mesoderm?

Answer 25

• heart
• blood
• spleen
  (splanchnic and somatic)

Question 26

what will the yolk sac become?

Answer 26

the gut tube

Question 27

endoderm derivates examples

Answer 27

• pancrease
• stomach
• liver
  THE GI AND RESP TRACT

Question 28

ectoderm derivates examples

Answer 28

• epidermis
• nails and teeth
• eyes
• epithelium
• glands

Question 29

Name each part of the mesoderm

Answer 29