Embryological Origins Flashcards
What process of cellular division creates gametes?
meiosis
What are the names of mammalian gametes?
sperm and egg
What sort of cells are gametes?
haploid
During fertilisation what type of cell is created?
diploid cell
When is sex determined?
when the first diploid cell is formed and the chromosomes are released into the ovum
What is the first diploid cell known as?
zygote
on what day does the first cell division happen in humans?
day 1/2 in humans
what sort of cell division is occuring once the zygote is formed?
mitosis
What happens to the size of the cells as mitosis continues in the zygote?
cells become smaller
What is they zygote then known as?
morula
What is the name of the edge of the uterus where the morula fuses?
isthmus
What is the zona pellucinda?
outer shell of the morula
What are totipotent cells?
cells that can become anything during differentiation
What might totipotent cells be used for?
the embryo or the placenta
What are pluiripotent cells?
cells that have differentiated but may form any tissue in the embryo
What do the inner and outer cells of the morula become?
inner cells become embryoblast and the outer cells become trophoblast
What will the trophoblast and embryoblast go on to become?
embryoblast-embryo and trophoblast-placenta
What are the two types of differentiation found in stem cells?
undifferentiated or partially differentiated
What type of cells are the most versitile as stem cells?
totipotent zygote cells
What happens during implntation?
blastocyst attaches to the uterine wall
What happens in species which carry litters?
the blastocysts spread evenly along uterine horns
What two areas are created during embryoblast differentiation?
epiblast and hypoblast
What does the epiblast contain?
amniotic cavity
what does the hypoblast contain?
yolk sac
what is a key feature of the outer layer of the trophoblast?
non antigenic
What is the outerlayer of the trophoblast known as?
syncytiotrophoblast
What is so important about the syncytiotrophoblast being non antigenic?
they interfere with maternal cells but are not rejected/trigger an immune response
What are the combined epiblast and hypoblast known as?
bilaminer germ disk
What is gastrulation?
formation of trilaminer germ disk and body tissue type cell derivative lines
What are the three separate germ layers?
ectoderm, mesoderm and endoderm
What are the three layers converted from?
epiblast and hydroblast
How is the primative streak formed?
proliferating cells migrate to centre at caudal end
Where does the primative streak originate from?
primative node
What is the main group of cells that migrate through the primative streak?
epiblast
What is the ectoderm formed from?
cells that remain in the epiblast
what is the mesoderm formed from?
epiblast cells that migrate into the middle layer of bilaminer germ disc
What is the endoderm formed from?
cells which displace the hydroblast
What does the ectoderm go on to form?
central nervous system, peripheral nervous system, eyes ears and skin
what does the mesoderm go on to form?
connective tissues, blood, bones and muscle
What are the 3 subsections of the mesoderm?
paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm
What does the paraxial mesoderm form?
musculoskeletal system
What does the intermediate mesoderm form?
urogenital systems
What does the lateral plate mesoderm form?
muscular gut wall and partial body wall
What does the endoderm go on to form?
GI tract organs, epithelium of GI and respiratory tract
Why do all three layers form different things?
ectoderm is folded around the outside of embryo while endoderm is folded innermost
What body system is developed during neuralation?
CNS
What is formed during neuralation?
neural tube
What is the notochord?
increase of poraxial mesoderm along the longitudanal axis of the embryo
What does signalling from the notochord cause?
proliferation of mesoderm
What does the proliferation of the mesoderm cause in ectoderm?
movement and change of shape in overlying ectoderm
Where does neuralation begin and end?
begins centrally and moves cranially and caudally
Describe the 4 stages of neuralation?
ectoderm changes shape creating neural grove over the notochord and neural folds on either side. neural groove becomes more pronounced as do neural folds. Neural crest cells form lateral to the top of the neural fold, neural crest formed at the most accute angle of fold. Neural crests meet and form neural tube, skin covers neural tube, neural crest cells present laterally to neural tube
What do the rostral and caudal ends of the spinal chord form?
rostral: brain, caudal: spinal chord
What can happen if the neural tube fails to close?
if rostrally/cranially: anecephally. If caudally: spina bifida or dermoid sinus
What is anecephally?
open brain and lack of skull vault
What other process is neuralation linked to ?
cell folding and growth
In what directions does the cell grow?
laterally and caphalocaudal
What does caphalocaudal mean?
head to toe
What does lateral and caphalocaudal folding and growth lead to the formation of?
formation of body cavities and connecting stalk (connection with placenta)
What happens during lateral folding?
ectoderm streached around the outside of the body (forms skin), yolk sac (endoderm) is pinched off, primative gut tube brought inside main embryonic cavity
What happens during caphalocaudal folding?
amniotic cavity pulled down at cranial and caudal ends of embryo. Heart cells and tube are pulled inside the embryo
