Embryology Flashcards
what are the three layers of the derm layers?
ectoderm
mesoderm
endoderm
what layer of the term trilaminar plate forms the nervous system?
ectoderm
what layer of the term trilaminar plate forms the bone?
mesoderm
what layer of the term trilaminar plate forms the gut?
endoderm
what layer of the term trilaminar plate forms the lungs?
endoderm
what layer of the term trilaminar plate forms the epidermis ?
ectoderm
what layer of the term trilaminar plate is in contact with the yolk sac?
endoderm
at which week does the CNS start to appear?
3rd week
what is formed from the thickening of the ectoderm anterior to the primitive node?
neural plate
what causes the neural plate to form?
primitive node sends out signals
what are the thickened edges of the neural plate called?
neural folds
what day does the neural plate start to fold ?
day 20
where is the first area the neural tube starts to fuse?
in the middle
at what day does the anterior and posterior neuropore both close ?
day 27
what neuropore closes first?
the anterior or posterior
the anterior closes first at day 25
the posterior closes at day 27
what is another name for the anterior neuropore ?
the rostral
before the neural tube closes, is it in contact with amniotic fluid ?
yes
what is the depression down the neural tube called?
neural groove
what shape do the cells in the neural groove change from and to ?
columnar -> wedge shaped
what are the three main neural tube defects ?
Anencephaly
Encephalocoele
Spina bifida
what defect occurs during anencephaly ?
failure of the anterior neuropore closure
what would result in the anterior neuropore not closing?
the neural tube is in contact with the amniotic fluid so the skull and brain can’t form properly
can’t people with anencephaly survive?
no
- usually still birth
is anencephaly more common in males or females ?
x4 common in females
what defect results in encephalocoele?
when the rostral neuropore doesn’t close properly and cerebral tissue herniates through the skull defect
in what areas is the skull defect most common in encephalocoele?
occipital and fronto-nasal area
what common defects post birth does encephalocoele result in due to the areas of brain which is affected?
vision impairment and emotion and cognitive impairment
what do the degree of neurological deficits depend on ?
- part of brain affected
- area of brain affected
out of the three most known neural tube defects which one is most common?
spina bifida
is anencephaly and encephalocoele common?
no they are rare
what defect results in spina bifida ?
defect in the closure of the caudal (posterior) neuropore and the vertebral arches don’t fuse
are there different subtypes of spina bifida ?
yes three main subtypes
what are the three sub types of spina bifida ?
meningocele
meningomyelocle
myeloschisis
which of the three subtypes of spina bifida are most severe?
myeloschisis
has the incidence of spina bifida been increasing or decreasing ?
decreasing
state two reasons why spina bifida incidence is decreasing?
- folic acid supplements
- prenatal screening
what is the rarest type of spina bifida ?
meningocele
what three tests can be done prenatal to test for spina bifida ?
- blood test for alpha fetoprotein (increased)
- amniocentisis
- ultrasound
What three risk factors are there for neural tube defects?
- genetic predisposition
- nutritional
- environmental
how many primary vesicles are there?
3
what are the three primary vesicles called?
prosencephalon
mesencephalon
rhombencephalon
what week do the primary vesicles form?
4th week
what week do the secondary vesicles form?
5th week
what are the three flexures in the neural tube are there?
cephalic
pontine
cervical
what structures does the cephalic flexure divide?
midbrain and hindbrain
what structures does the pontine flexure divide?
the two vesicles in the hindbrain
what structures does the cervical flexure divide?
the hindbrain and spinal cord
what structures are formed from the telencephalon ?
cerebral hemispheres, hippocampus, basal ganglia
what structures are formed from the diencephalon ?
thalamus
hypothalamus
pituitary gland
pineal gland
what structures are formed from the mesencephalon ?
superior and inferior colliculi
what structures are formed from the metencephalon ?
cerebellum and pons
what structures are formed from the myelencephalon ?
medulla
what week does CSF start to be formed?
5th
what produces CSF?
choroid plexus
in which ventricle does the CSF drain into the subarachnoid space?
4th ventricle
where does the CSF reabsorbed back into venous system ?
arachnoid villi
is CSF continually being replaced?
yes
what is the condition when there is a blockage in the ventricles and CSF can’t circulate properly?
hydrocephalus
what ventricle is most commonly blocked during hydrocephalus ?
cerebral aquaduct
what are some causes of hydrocephalus ?
genetic
prenatal viral infection
intraventricular haemorrhage
spina bifida cystica
what cells are present as a single layer around the neural tube which go on to form neurons and glial cells?
neuroepithelial cells
what four cells are produced from neuroepithelium in the CNS?
neuron
astrocyte
oligodendrocytes
ependymal cell
which cell in the CNS is not produced by neuroepithelium ?
microglia
- which comes from mesenchymal cells
what are the two types of astrocytes ?
protoplasmic
fibrous
what is the function of astrocytes ?
maintains BBB and supports neurons
which cells form the PNS?
neural crest cells
state some structures the neural crest cells form?
dorsal root ganglia
sympathetic ganglia
parasympathetic ganglia
at which month is the spinal cord the same length as the vertebrae?
3 months
at birth what spinal vertebrae does the spinal cord finish at?
L3
as an adult what spinal vertebrae does the spinal cord finish at?
L1
what are the hills and depressions in the cerebrum called?
hills = gyrus depressions = sulci
what are the hills and depressions in the cerebellum called?
hills = folia depressions = sulci
what is the advantage of having sulci and gyri in the cerebrum?
increases surface area and hence more cells and information can be fitted in the small area of the brain
what is the very rare disorder when sulci and grey don’t form on the brain?
lissencephaly
what causes lissencephaly?
when there is defective neuronal migration
what is polymicrogyria ?
when there are many small gyri
what does polymicrogyria result in?
connection defects which results in neurological problems such as retardation, seizures and motor deficits
what condition is caused by the zika virus ?
microcephaly
what is the condition called when there is defected connection between the two hemispheres of the cerebrum ?
aegenesis corpus callosum
what is the condition when there are CSF filled cysts in the cerebrum ?
porencephaly
what condition results in large clefts or slits in the cerebrum ?
schizencephaly
what condition results in the spinal cord being divided into two?
diastematomyelia
what is a common cause of intellectual impairment in children?
maternal alcohol abuse
why is the CNS vulnerable to defects form alcohol?
the CNS develops early in the 3rd week, therefore some women may not even realise they are pregnant so may continue drinking which could cause CNS defects
what is the incidence of foetal alcohol syndrome per 1000?
1:1000
what is the incidence of spina bifida per 1000?
1:1000
as well as alcohol state some causes of intellectual impairment in children?
genetic (downs) radiation infection birth trauma postnatal insults (meningitis)
