L1a - embryology Flashcards
stages of development from oocyte to blastocyst
Oocyte > fertilisation > pronuclei > 2 cell stage > morula > advanced morula > blastocyst > implantation
How long after the fertilisation does the stages of blatsocyst development occur
from 0 to 6 days
how does dizygotic twins form
when the fertilised oocyte spilt in half to get 2 oocytes
what is pronuclei
when male and female nuclei approach each other and fuse together
what does the sprem contribute
centroiles
what does the egg contribute to the zygote
mitochondria
what is zona pellucida
- layer of prote ction surrounding the egg
what happens once the zygote has reached 8 cell stage
forms inner cell mass (ICM) and outer cell mass (OCM)
what does the ICM develop into
- epiblast (+ amniotic cavity)
- hypoblast (+ yolk sac) , forming an Embyro
what does the OCM develop into
trophoblast then placenta
what is pumped into the OCM forming blastocyst
fluid creating blastocyst cavity
what is OCT4
TF
function of OCT4
maintain pluripotentcy and involved in self renewal.
what happens to the embyro if it lacks OCT4
no ICM and no pluripotency
trophoblast differentiates into what layers
cytotrophoblast
synytiotrophoblast
what is gestrulation and how long after fertilisation does it occur
early developmental process where the embryo reorganises itself to multi structure called gastrula
- 15 days
what appears that initates gestrulation
primitive streak and primitive node
what happens to the cell of epiblast when primitive streak appear
they migrate beneath it between epiblast and hypoblast Or
- displace the cells of hypoblast
- this migration forms gastrula layers
what are the gastrula layers
endoderm
mesoderm
ectoderm
what controls the epiblast cell migration forming the gastrula layers
FGF8
FGF8 is synthesised by what
primiative streak
endoderm develop further into what body strcutures
GIT, respiratory tract, urinary system
mesoderm develop further into what body strcutures
connective tissue, cardiovascular system, blood cells
ectoderm develop further into what body strcutures
Nervous system , teeth, epidermis
what is formed after the gestrulation , 17-18 days after fertilisation
Notochordal plate comes from the endoderm and forms notochord
function of notochord
important site for signal secretion for NS development
- located in mesoderm
3 signalling molecules released by Primitive node
nodal, BMP4, chordin/nordin
funtion of nodal
maintain primitive streak and upregulates BMP4 and chordin and noggin
function of BMP4
- forms skin from ectoderm
function chordin/noggin
block BMP4
- forms NS and cranial structures
what gene is important for cranial development
GSC gene
what protein does the GSC gene code for
goosecoid
function of goosecoid
stimulates production of molecules like cerberus
- so the head can develop
