by mtoom


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What is neurulation?
Formation and closure of neural tube
When does neurulation occur?
Neurulation occurs in 3rd week of intrauterine life
What induces the surface ectoderm?
  • What are the next couple of steps? (5)
Notocord
  • Induces surface ectoderm
  • Midline cells proliferate
  • Form thickened epithelium which folds
  • Neural tube closes
  • Surface ectoderm separates
Where does closure begin?
  • What directions does it proceed?
Closure begins in the cervical region
  • Proceeds in both upwards (cranial) and downwards (caudal) directions, in a zip-like fashion 
What are the last regions to fuse in neurulation?
  • Anterior (rostral), 25th day
  • Posterior (caudal), 27th day
The neural canal forms what 2 structures?
  • Central canal of spinal cord
  • Ventricles of the brain
Where are neural crest cells formed?
  • What is the origin of neural crest cells? 
Formed at the crests of the neural fold
  • Ectoderm 
What do neural crest cells detach from?
Detach from the surface ectoderm
Neural crest cells are damaged when mom does what?
  • Results in what syndrome? 
Drinks Alcohol
  • Fetal alcohol syndrome 
Fetal alcohol spectrum disorder (FASD) has what symptoms/effects? (5)
  • Mental retardation
  • Low birth weight
  • Delayed psychomotor skills
  • Facial abnormalities
  • Delayed psychological manifestations 
What are the 3 types of neural tube defects (spina bifida) in order of increasing severity?
  • Occulta
  • Cystica
    -Meningocele
    -Meningomyelocele 
  • Myeloschisis
Regarding neural tube defects, explain each a bit further:
  • Spina bifida occulta
  • Meningocele
  • Meningomyelocele
  • Myeloschisis 
  • Spina bifida occulta
    -Cord/dura are normal but spine incompletely closed 
  • Meningocele
    -Pouch of CSF-filled dura protrudes out of back 
  • Meningomyelocele
    -Pouch of CSF filled dura containing spinal cord protrudes out of back 
  • Myeloschisis
    -Spinal cord split open and exposed 
What happens when the anterior neuropore fails to close? *
Anencephaly (meroencephaly)
What are the neurological issues associated with neural tube defects? (4)
  • Skeletal muscle paralysis
  • Loss of anal and urethral (bladder) sphincter activity
  • Saddle anesthesia
  • Spina bifida cystica associated with Arnold-Chiari malformation 
What is the etiology of spina bifida?
Multifactorial
How is spina bifida diagnosed? (2)
  • Ultrasound (8 weeks)
  • Alpha-fetoprotein (maternal serum, amniotic fluid) 
How do you prevent spina bifida? (1)
  • 0.4mg folic acid daily before and during pregnancy
At what level is the spinal cord in each stage of development? (3)
  • 3rd month
  • Birth
  • Adult 
  • 3rd month → Coccyx
  • Birth → L3
  • Adult →  L1/L2
Difference between cauda equina and filum terminale?
  • Cauda equina: Spinal nerves
  • Filum terminale: Fibrous tissue that anchors spinal cord
Why are the lower spinal nerves really angulated in adults?
Because spinal cord does not grow as fast as vertebrae
  • Spinal cord gets left behind 
With the closure of the anterior neuropore, the cranial end of the neural tube shows what?
3 Dilatations
What do the 3 dilatations in the anterior neuropore form?
The 3 dilatations form the primary brain vesicles
What are the 3 primary brain vesicles? (provide both names)
  • Forebrain (Prosencephalon)
  • Midbrain (Mesencephalon)
  • Hindbrain (Rhombencephalon)
What 2 structures form from the forebrain (prosencephalon)?
  • Telencephalon
  • Diencephalon
What 2 structures form from the hindbrain (rhombencephalon)?
  • Metencephalon
  • Myelencephalon
What structures form from the telencephalon? (1)
Cerebral hemispheres
What structures form from the diencephalon? (2)
Hypothalamus
Pituitary
What structures form from the mesencephalon? (3)
  • Midbrain
  • Cerebral peduncles
  • Superior/inferior colliculi
What structures form from the metencephalon? (2)
  • Pons
  • Cerebellum
What structures form from the myelencephalon? (1)
Medulla oblongata
What are the 3 flexures of the brain?
  • Cervical flexure
  • Midbrain flexure
  • Pontine flexure
Describe what is demarcated by each flexure?
  • Cervical flexure
  • Midbrain flexure
  • Pontine flexure
  • Cervical flexure
    -Demarcates brain and spinal cord 
  • Midbrain flexure
    -Demarcates forebrain (cerebral hemispheres) from midbrain 
  • Pontine flexure
    -Demarcates hindbrain from midbrain 
What are the consequences of the brain flexures? (2)
  • Alteration in basic arrangement of cell groups and nerve fibers
  • Flexure in pontine region causes a thinning of dorsal wall (roof) of brain
What happens to brain structure as you move from the spinal cord to the myelencephalon?
  • At what structure does this occur? 
The roof plate opens up
  • Occurs at pontine flexure 
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