embryology Flashcards
what is morphogenesis?
shape formation of tissues, organs and organisms
what processes determine shape?
growth
differentiation
motility
induction- interaction between cells apoptosis
what are one of the two states that cellls exist in during the early embryo stage
-epithelial cells: tightly connected in sheets or tubes
-mesenchymal cells: unconnected and operate as independent units
what is induction? how is it achieved? what is it often dependent on?
-the influence of once cell or tissue (inducer) on the developmental fate of an adjacent cell or tissue (responder)
-achieved by the diffusion of a chemical signal to nearby tissue
-often dependent on previous interactions that have primed the target tissue
what is the embryonic period?
the moment from fertilisation top the end of week 8 of development
what is the foetal period?
week 9 to week 36 of development
what happens during the first stage of fertilisation?
- sperm binds to the zona pellucida and releases digestive enzymes
2.the sperm fuses with the plasma membrane - this triggers the egg activation process
- cell cycle resumes
- egg metabolism is activated
- polyspermy is prevented
what happens at at Carnegie stage 1
you have a single celled zygote being a fertilised oocyte
how many genes does mitchondrial dna encode? what are some diseases that a mutation of some of these can cause?
37
-motor neuron disease
-parkinson’s
-neuropathy, ataxia, retinitis pigmentosa and ptosis (NARP syndrome)
-leber’s optic atrophy/ leber’s hereditary optic neuropathy (LHON)
what is LHON caused by and what is the sequence of symptoms?
caused by mutations in the mitochondrial DNA coding a subunit of enzyme NADH
1. onset in young adulthood
2. blurring of central vision
3. desaturation of colour
4. central vision deteriorates to counting fingers in 80%
5. optic atrophy
6. permenant large scotoma
what is compaction?
where the 8 cell stage zygote cells become compacted so expression of cadherins and formation of adhering junctions
describe when does cavitation and blastocyst formation occur?
at the 16 cell stage a fluid filled cavity being a blastocoel is formed within the ball of cells by the action of sodium pumps forming a blastocyst
what does the trophoblast form?
the foetal part of placenta and other extraembryonic tissue
what happens at Carnegie stage 3?
the blastocyst hatches from the zona pellucida shell
what day does implantation start and when is it complete?
starts at day 5 to 6 , its complete by approx. day 12
where are totipotent stem cells from and what do they do?
in the morula of the embryo and can give rise to every cell in the body and form an entire organism
where are pluripotent stem cells from and what do they do?
in the inner cell mass of a blastocyst and can generate virtually all cell types apart from the placenta
where are multipotent stem cells from and what do they do?
found at specific sites as they are adult stem cells/ progenitor cells, they can only give rise to a limited number of cell types
what can iPSCs be used for?
treatment of retinal degenerative diseases
how has retinal stem cell transplant been demonstrated?
retinal stem cells from the ciliary margin of human donors were transplanted into the mouse retina and some transplanted cells differentiated into photoreceptors and others into RPE cells
what happens at week 2 of embryonic development?
-completion of implantation
-formation of bilaminar germ disc
how does the bilaminar germ disc form?
the inner cell mas divides to form
-epiblast which divides top line aminotic cavity and form all tissues in embryp
-hypoblast likes blastocoel and gives rise to the yolk sac
what happens at week 3 of embryo development?
gastrulation and then neurulation
what is the first sign of gastrulation? what is it? what does it establish?
-the formation of the primitive streak
-its where the epiblast cells ingress forming a furrow at the tail end of the embryonic disk
-the streak establishes the longitudinal axis of bilateral symmetry in the embryo
what is the process of gastrulation?
-gastrula and blastula are formed
-2 layer embryo is converted into a 3 layer
-the 3 primary germ layers are formed:
ectoderm e.g. CNS, epidermis, endoderm e.g. lung, thyroid, mesoderm e.g. heart, muscle
what does neurulation begin with?what is it? What does this do?
formation of the notochord which is a flexible rod
it induces the formation of the CNS by signalling to the ectoderm layer above it to form the neural plate
when does neurulation occur?
a bit after gastrulation while it is still occuring
what is neuralation?
the folding process that forms the neural tube at which stage the embryo is referred to as the neurula
give the process of neuralation
- formation of notochord
- formation of the neural plate,
- formation of the neural tube
- closure of the neuropores where it ends at day 23-24
- leads to the formation of brain and spinal cord
- leads to neurocrest formation
where do the neural crest cells originate and where do they end up?
they originate from ectoderm at the top of the neural tube and then migrate extensively
What is the embryonic origin of the corneal epithelia and stroma?
-neural crest
-surface ectoderm
which parts of the eye and adnexa are formed from the mesoderm?
the retina
which parts of the eye are derived from the neural cres?
-corneal endothelium
-choroidal melanocytes
-corneal stroma
from which part of ectoderm are the retinal neurons and retinal pigment epithelium originate from?
-the neural tube
-the neural ectoderm
What stages of embryonic development does the zona pellucida surround the dividing cells of an early embryo?
-morula
-initial cleavage of the zygote
what parts of the eye and adnexa are formed from the mesoderm?
-sclera
-blood vessels
-ciliary muscles
-bones of the orbit
