Congenital Diseases Associated With The Central Nervous System Flashcards
What does the neural tube give rise to?
Brain Spinal cord Cranial and spinal nerves Eyes and other sensory organs Neural crest
When is the neural tube formed?
In gastrulation at week 3/4
What happens as the neural tube closes?
Becomes patterned along the dorso-ventral and rostro-caudal axis
What are defects classified according to?
Stage thought to be affected
What are the classifications of neural tube defects?
Early CNS patterning
Neural tube closure
Regional brain defects
What is an example of an early CNS patterning defect?
Holoprosencephaly
What are some examples of neural tube closure defects?
Chraniorachischsis
Exencephaly
Spina bifida
How many neural tube closure points are there?
Three main and two others
Where is the first closure of the neural tube?
Between hindbrain and spinal cord
Where is the second closure of the neural tube?
Between forebrain and midbrain
Where is the third closure of the neural tube?
Most rostral portion of forebrain and only progresses posteriorly
Where is the fourth closure of the neural tube?
More rostral and within the hindbrain than closure 1
Where is the fifth closure of the neural tube?
Most posterior point so only progresses anteriorly
What are the two modes of neural tube closure?
Primary or secondary neurulation
What happens in primary neurulation?
Rolling up of tube
Closure is by fold apposition then ‘zipping up’
What is secondary neurulation?
Tunneling or hollowing of tail bud
What are the steps in primary neurulation?
Shaping Folding Elevation Convergence Closure
What happens in the shaping step of primary neurulation?
Narrowing along the mediolateral axis and extend along the rostro-caudal axis
What happens in the folding step of primary neurulation?
Occurs by the establishment of hinge points along the neural plate
What is the first hinge point to appear in primary neurulation?
Midline hingepoint
What happens in the elevation step of primary neurulation?
Lateral wings of neural plate to fold up
What happens in the convergence step of primary neurulation?
More hinge points formed next to the neural crest which allows for the rounding of the plate
What causes the cell wedging at hinge points in primary neurulation?
Microtubules and actin filaments
What is primary neurulation controlled by?
Planar cell polarity pathway
