W9- Lecture 49- Gastrulation and Neurulation

Question 1

what is Gastrulation?

Answer 1

The process by which the 3 germ layers are formed

Once committed to a particular germ-layer lineage, cells cannot switch to the fate of cells from a different lineage

Question 2

what structures do the germ layers form ?

Answer 2

Ectoderm Epidermis
Nervous system
Pigment cells

Mesoderm	Kidneys
			Gonads
			Bones
			Muscle
			Heart
			Blood cells
			(Part of most internal organs)

Endoderm Lining of gut
Respiratory system

Question 3

the inner cell mass (ICM) differentiates into two layers called

when / where

Answer 3

bilaminar disc with
the amniotic cavity above
and the blastocoel below

In the blastocyst, around the time of implantation,

Question 4

what does the epiblast develop into ?

Answer 4

Embryonic epiblast to the embryo

Amniocytes to the amnion secretes fluid to the amniotic cavity

Question 5

what does the hypoblast develop into ?

Answer 5

lines blastocoel to the yolk sac

Question 6

Gastrulation reorganises the epiblast into what ?

Answer 6

trilaminar disc of

ectoderm, mesoderm & endoderm

Question 7

describe the position of the epiblast and hypoblast in terms of each other

Answer 7

epiblast higher layer

hypoblast lower layer

Question 8

in which direction does the primitive groove/streak form away from the node ?

Answer 8

posteriorly

Question 9

describe the process of gastrulation ?

will be printing tho

Answer 9

Formation of primitive streak & node in epiblast

Posterior extension of streak

Migration of epiblast cells through node  endoderm, anterior notochord & prechordal mesoderm

Migration of epiblast cells through streak  ventral & lateral mesoderm.

Regression of streak & replacement by notochord

Question 10

what is neurulation ?

where within the embryo does this take place ?

Answer 10

The formation of the neural tube

happens in neural plate

Question 11

how many hinge regions are there in neurulation

Answer 11

3

Question 12

what causes the folding found in neurulation?

Answer 12

Proliferation of ectodermal cells causing the folding

Question 13

mesodermal tissue is where you find the neural plate what layer is the neural plate formed in ?

Answer 13

in the ectoderm

Question 14

what two conditions take place if the folding and fusing of the neural plate is incomplete ?

Answer 14

Failure of complete fusion
spina bifida- posteriorly
anencephaly- anteriorly

Question 15

what happens if nutrients are deficient during neurulation ?

example

Answer 15

If nutrients are deficient cell will not be able to proliferate + major issue
folate
thymidine produced by folate
Thymidine – rate limiting step (slowest out of amino acids )
Dna needed as cells proliferate
thymidine important for DNA

Question 16

what do clusters of neural cells form ?

where

Answer 16

future nerves & pigment cells

in ‘crests’ dorso-laterally to tube