Physiological and Pathological formation of the brain and spinal cord Flashcards
Gastrulation (3rd week development)
Ectoderm: skin, nervous system
Endoderm: epithelial lining of gut and respiratory system, liver, pancreas
Mesoderm: Notochord, muscular system
Development of spinal chord
Ectoderm thickens in midline to form the neural plate
Up until the end of the 4th week…
1) The notochord forms from mesoderm cells soon after Gastrulation is complete
2) signals from notochord cause inward folding of ectoderm at the neural plate
3) Ends of neural plate fuse and disconnect to form an autonomous neural tube
Lateral to the neural groove lie presumptive neural crest cells
Abnormalities of the spinal cord
The neural tube usually closes at the end of 4th embryonic week
Failure to close cephalic region – anencephaly
Failure to close spinal region – spina bifida
Collectively called – neural tube defects
Environmental factors are folic acid and maternal diabetes
Syndromic (monogenic) causes of NTD have a higher recurrence risk
Meckel Syndrome:
NTD
Cystic kidney malformation
Extra fingers
¼ chance of a sibling being affected
Development of the brain- 4 weeks
Prosencephalon – cerebral hemispheres and thalamic structures
Mesencephalon – midbrain
Rhombencephalon – medulla, pons and cerebellum
What is microcephaly?
Reduced head circumference
Macrocephaly
Increased head circumference
Cerebrospinal fluid circulation
CSF circulates through the subarachnoid spaces and through the ventricles
CSF cushions the brain and helps circulate metabolites
Around 120 mLs
Produced as filtrate of blood at choroid plexuses in ventricules
Absorbed via arachnoid granulations in superior sagittal sinus
Hydrocephalus
Accumulation of CSF with increased intracranial pressure
Can cause macrocephaly in children (therefore always scan increasing head size)
Obstructive (non-communicating): e.g. tumour, haemorrhage
Non-obstructive (communicating): e.g. increased CSF production
