3: L12 Flashcards
3 Main events of development
Cleavage
Gastrulation
Organogeneisis
2 main principals in cleavage
cell division
pattern formation
main principal in Gastrulation
morphogenesis
2 main principal in Organogeneisis
Cell differentiation
growth
As cleavage proceeds what are 3 stages of the cell ball names
oocyte > morula >blastula
what are the factors that increase and decrease with cleavage proceed
decrease cell division
decrease maternal determinants
inc embryonic gene expression
What is change of plane in cleavage influenced by
by yolk amount
o High – Vegetal pole
o Low – Animal Pole
o Mammals - +/- yolk free (don’t see change in plane as much) - placenta
describe 2 processes of cleavage pattern formation
• Localisation of cytoplasmic factors (specific mRNAs & proteins) used as morphogenetic information to lay blueprint for body plan
o (body axis formation)
• Maternal vs zygotic factors A-P & V-D
o Determines spatial and temporal distribution
what is gastrulation- morphogenesis
formation of 3 germ layers (mesoderm, ectoderm, endoderm)
do zygotic gene expression inc or decrease when cleavage ends
inc
how does blastula rearrange into 3 layers
internalisation and 2. migration
what do ecto, meso and endo turn into
ecto- skin + NS
Meso- most organs
endo- linings of digestive and respiratory
what is gastrulation dependent on
organizers
what does an organiser do
• Responsible for initiating and coordinating specific differentiation patterns, but also in a temporal and special way, driving this process of moving cells from one region to another to set up these three layers
what are organisers called in mammals and birds
o Mammals= Spemann organizer
o Bird: Hensens node
what determines location of organiser
• Sperm entry
what are autonomous and cell conditioning signals in organizer function
Autonomous’ signals: zygotic transcription factors (influence own environment) or
2. Cell conditioning signals: zygotic secretion factors (diffuse away from cell and influence other cells)
what are vegetable animal and marginal cells turn into
- Vegetal= endodermal cells
- Animal= epidermal
- Marginal= mesoderm
what is morphogen
a signal molecule that imposes a pattern on a field of cell
i.e. concentration gradient
3 axis of developmetn
A-V animal veg
(internal/external)
AP anterior posture (head + tail)
DV dorsoventral (back and belly)
describe neurulation in organogenesis
• Neural tube + below it = gives signals to give instructions to cells to become dorsal/ventral/lateral
Where does the CNS come from and how
• CNS comes from neural plate(at cranial region towards causal) via signals such as inhibition of bone morphogenetic protein (BMP) signalling
- Within neuro ecto derm region, BMP production inhibition initiates migration and division= produces neural folds (which fuse together)
- Production of ventralising signals (via sonic hedgehog on neural plate location where vaginisation is occuring= together forms neural tube
- Invagination complete + ecotderm plate seals itself up again
- Proteins maintain dorsal and ventral polarity // continue secrete factors (allows PNS)
what process gives rise to fingers
apoptosis
Describe organogenesis example brain compartmentalisation
(defines boundary between mid-and hindbrain)
• Some inhibitory and promotion factors drive process + gives rise to distinct neural tissue
o Differential expression allows process to proceed
o Movement= formation of Forebrain, Midbrain, hindbrain
• Process continues= Further 3d structure form
