EMBRYOLOGY Flashcards
Morula
first clump of cells after fertilisation - 16 cells
blastocyst
more than 16 cells
blastocele
hole in the middle of blastocyst
gastrulation
single layer blastula developing into a tri-laminar disc (gastrula)
embryo develops into trilaminar disc made up of :
- ectoderm
- mesoderm
- endoderm
Neuraltion
process of formation of embryonic nervous system
(1) 3rd week of embryonic development and neuraltion
ectoderm thickens in the midline to form neural plate
(2) After formation of neural plate what happens in embryonic development
ectoderm undergoes differentia mitosis to cause formation fo a midline groove = NEURAL GROOVE
(3) After neural groove what happens in embryonic development
neural groove deepens and eventually detached from the overlying ectoderm to form the NEURAL TUBE
(4) what lie lateral to the neural plate and what do these do in embryonic development
Lateral to neural plate lie presumptive NEURAL CREST CELLS which run dorsolaterally along the neural groove
these develop to form many cells types e.g
- Sensory (dorsal root) ganglia of the spinal cord and cranial nerves V, VII, IX, X
- shwanna cells
-pigment cells
- adnrenal medulla
- bony skull
- meninges
- dermis
(quite a lot of head and neck made from neural crest cells)
(5) What part of neural tube develops faster than the other and what does this develop into
rostral (e.g. superior) portion of neural tube - which develops into brain (CNS),
grows faster than caudal (i.e. inferior) - which develops into spinal cord
(the central cavity within the neural tube becomes the central canal of the spinal cord and the ventricles of the brain)
(6) by the 5th week of embryonic development what can be identified?
three primary brain vesicles:
1 PROCEPHALON (forebrain) 2 MESENCEPHALON (midbrain) 3 RHOMBENCEPHALON (hindbrain)
(7) by the 7th week, further differentiation occurs resulting in the formation of secondary brain vesicles:
1 Procephalon => Telecephalon & Diencephalon
2 Mesencephalon = Mesencephalon
3 Rhombencephalon => Metencephalon & Myelencephalon
look at pic lol
(8) Secondry brain vesicles give rise to derivatives in mature brain:
Telecephalon=
Diencephalon =
Mesencephalon=
Metencephalon =
Myelencephalon=
Telecephalon– Cerebral hemisphere & Lateral ventricles
Diencephalon – Thalamus, Hypothalamus & third ventricle
Mesencephalon– Midbrain (colliculli) & aqueduct
Metencephalon– Cerebellum, Pons, upper part of 4th ventricle
Myelencephalon – Medulla oblongata & lower part of 4th ventricle
Neural tube usually closes when? and what does failure of this in the spinal cord cause?
end of 4th week
Spina bifida
Failure of neural tube closing in Cephalic region causes ?
anencephalus
reasons for failure of neural tube closing?
-faulty induction
-environmental teratogens (egents disturbing development)
acting on neuroepithelial cells
developmental milestones:
3 weeks 10 weeks 3 months 5 months 7 months 9 months
3 weeks - eye formation
10 weeks - cerebral expansion & commissures
3 months - basic structures established
5 months - Myelination has begun
7 months - lobes cerebrum has formed
9 months - gyri & sulci formed
Abnormalities to CNS are dependant on time of infection;
6th week =
9th week =
5th- 10th week =
CNS Disorders generally occur in 2nd trimester
risk of disorder falls after … weeks due to fact most CNS structures developed by this time
6th week = eye malformations e.g. cataracts
9th week = Deafness can occur e.g. organ of corti
5th- 10th week = cardiac malformation
16 weeks
Innervation fo dermal skin from
28 weeks
Non noxious
means no pain detected e.g
dorsal root ganglion connects to spinal cord from 8 weeks but this is non noxious
C-Fibre connection
(noxious (painful) Stimuli ) from 19+ weeks
Organised thalamus what weeks
from 8+
retinal inputs work at what weeks ?
14-16 weeks
Myelination occurs when
from 25 weeks
speed of conduction increases with myelination
connections from thalamus to cortex occur from
24 weeks
