Embrylogy Flashcards
What is the neural tube made of ?
Neuroectoderm
How does the neural tube form from the previous cord ?
the notochord directs the conversion of overlaying ectoderm to neuroectoderm . they form folds which fuse in the midline
Which way does the neural tube fuse ?
fusion at the anterior end (Neuropore) and then after posterior end
How does spina bifida normally occur?
Failure of fusion of the caudal neuropore
Where can spina bifida occur and what is its more serious form ?
occur anywhere most mostly in lumbosacral region.
More serious when neural tissue is near the skin .
hydrocephalus is very common
What happens in anencephaly?
failure of fusion of Anterior neuropore - foetus cannot survive
What is Rachischisis ?
failure of neural fold elevation
What 2 things help diagnose Neural tube defects?
Raised maternal alpha fetoprotein
USS
What can reduce risk of NTDs?
Folic acid 3 months before and after conception
How and when does the cauda equina form?
At what level does this occur?
At the 3rd month , vertebral column = spinal cord. after the vertebral column grows faster = spinal roots elongate to exit at the right foramen . L1
how are forebrain structures formed?
Primary vesicle = Prosencephalon –> telencephalon –> Cerebral hemispheres .
Prosencephalon –> dienceohalon –> thalamus
How are midbrain structures formed?
Mesencephalon –> mesencephalon –> midbrain
How are hindbrain structures formed ?
Rhombencephalon –> Metencephalon –> Pons, cerebellum
Rhombencephalon –> myelencephalon –> medulla
where does the NT fold in Brain to create the angle of the brain ?
Cervical flexure = between spinal cord and Rhombencephalon
cephalic flexure = between mesencephalon and rhombencephalon
What is the function of CSF?
to cushion brain and spinal cord in bony case
How does the ventricular system develop?
the secondary brain vesicles grow and the brain forms around the hollow tube .
What is hydrocephalus and how can it be treated ?
blockage of ventricular system seen in spina bifida . treated via shunt
How is the early neural tube layers organised from deep to superficial ?
Neuroepithelial = CSF secreting
Intermediate /mantle layer = neuroblasts
Marginal layer = processes
Where are the roof and floor plates on the neural tube ?
Roof plate = Dorsal
Floor = Ventral
What do the roof and floor plates go into? what are the new plates function
Roof = Alar plate = sensory
Floor = basal = motor
what separates the alar and basal plate ?
sulcus limitans
where are neural crest cells found ?
lateral border of the neural tube
What do neural crest cells do?
Become displaced enter into the mesoderm , transitioning from epithelial to mesenchyme
What are some structures that derive from neural crest cells ?
DRG, Sympathetic chain , Enteric ganglion , suprarenal glands .
What can happen in neural crest defects?
can affetc 1 structure e.g Hirschsprung’s
or affect many structures - Digeorge’s
