Embryology

Question 1

Primary Neurulation

Answer 1

1. induction of neuroectoderm of neural plate
2. elevatin form neural folds which come together and fuse
3. closure begins at cervical and moves rostrall and cadually
4. closes by 4th week

Question 2

2ndary neurulation

Answer 2

1. caudal part of tube forms from prmitive streak remains condense to form medullary cord
2. mesenchymal to epithelium cell transformtion
3. canalization
   - contribute to the sacral segments of CNS

Question 3

Brain flexures - where

Answer 3

1. midbrain @ mesencephalon
2. cervical @ spinomedullary jnc
3. pontine posteriorly

Question 4

Brain vesicles. describe development

Answer 4

5th week cranial end of neural tube forms vesicles- 3 1ary > 5 secondary.
Walls > brain and brain stem
Cavities > ventricles
Neural tube > spinal cord

Question 5

Ascent of spinal cord

Answer 5

• vertebral column growth outstrips spinl cord growth = appear like cord ascends
• results in:
  1. dissassosition bt vertebrae and cord segments
  2. cauda equina forms

Question 6

PNS development

-destinations of neural crest cells?

Answer 6

from neural tube (basal plates) and neural crest cells (sensory neurons of DRG, CN ganglia, postgang NS ganglia, enteric ganglia)

Question 7

Tissues of neural tube

Answer 7

neuroectoderm (1ry) mesoderm of primitive streak (2ndary)

Question 8

type of epi of neuroectoderm

Answer 8

pseduostrt columnr

Question 9

risk factors for neural tube defects

Answer 9

-history
-DM
-obesity
-anticonvulsant drugs
GIVE folic acid as prevention during preg

Question 10

anencephaly

Answer 10

rostral neural tube opening

-fatal

Question 11

myelochisis

Answer 11

• sensory issues below lesion

- hydrocephalis (water in brain - lemon sign of collapsed frontal bone, banana sign for pushed cerebellum)

Question 12

How are brain cells developed (histogenesis?)

Answer 12

1. neuron daugher cells from tube migrate to outer wall = INTERMEDIATE ZONE &raquo_space; grey matter: neurons, glial cells
2. internal layer to intermediate = VENTRICULAR ZONE&raquo_space; ependymal cells - line ventricles and canal
3. periphery: axons from intermediate zone = MARGINAL ZONE&raquo_space; white matter

Question 13

what are basal plates (floor plate)

Answer 13

neuroblast accumulate in ventral intermediate zone > LMN and pregang ANS neurons in ventral and later horn of spinal cord

Question 14

what are alar plates (roof plate)

Answer 14

neuroblast accumulate in dorsal intermedite zone > interneurons of dorsal horns for sensory pathway