well describes the development of nervous system from basic to advanced concept including neural tube defects. the concepts are presented in graphical form for easy understanding of concepts.

1. To MBBS 2nd year
Dr Laxman Khanal
Assistant Professor, Department of Anatomy
BPKIHS, Dharan, Nepal
12-02-2017
Development of
nervous system

2. Cranial nerves
1. Motor parts
2. Sensory parts
3. Autonomic parts
Parasympathetic
Spinal nerves
1. Motor parts
2. Sensory parts
3. Autonomic parts
A. Sympathetic (thoracic and lumbar
segment)
B. Parasympathetic (sacral segment)
Parts of nervous system
1. CNS- brain and spinal cord
2. PNS- cranial and spinal nerve
3. ANS- contributed by both CNS and PNS
ANS -cardiac muscle, smooth muscle and glands.

3. Notochord acts as an
inducer for development
of nervous system.
BMP
• Ectoderm
• Neuroectoderm
• Neural plate
• Neural fold
• Neural groove
• Neural tube
Neuroectoderm
 Neural tube
Edge of Neuroectoderm
and embryonic ectoderm
 Neural crest cells
Embryonic ectoderm
 Ectodermal derivatives

4. Development of
neural crest cells
Epithelial Mesenchymal
E- Cadherin

5. Pharyngeal arch derivatives
• Skeletal component
• Nerves and ganglia of each arch
• Dermis overlying each arch
• Blood vessels of face.
Migration of neural crest cells

6. Cranial neuropore
Closure at 25th day
Caudal neuropore
Closure at 27th day
Brain
SC
Alpha feto protein (AFP) increases
in maternal AF if neuropores fail to
close (neural tube defects).

7. Anencephaly Craniorachischisis
Neural tube defects of cranial part of neural tube

8. Neural tube defects of caudal part of neural tube
Rachischisis
Myelomeningocele
Spina bifida occulta

9. Prevented by maternal use of folic acid prior to and during pregnancy.
Spina bifida occulta Meningocele Myelomeningocele
Rachischisis

10. Anterior portion of neural tube forms
three primary brain vesicles.
1. Prosencephalon: Telencephalon + Diencephalon
2. Mesencephalon:
3. Rhombencephalon: Metencephalon + Mylencephalon
I & II CN
III & IV CN
V- XII CN

11. Development of ventricular system
4th

12. Development of spinal cord
L
TS neural tube
Neuroepithelial cells
L
Neuroblast cell
L
Mantle cell layer
Marginal cell layer
L
A
B
A
B
R
F
Anterior horn
Posterior horn
intermediate horn
Sensory
Motor
Autonomic

13. Neuroblast Glioblast
Microglial cells
Ependymal cells
Origin of various types of cells

14. Brain stem
Arrangement of alar and
basal plate is intact but
the arrangement is
different.
Higher center
Basal plate regress and
alar plate accentuate.
A
B

15. G
S
E
S
V
E
G
V
E
Development of functional columns in brain stem
Basal plate – motor components
Skeletal muscle
1. Somatic muscles - GSE
2. Pharyngeal arch muscles- SVE
Smooth muscle- GVE (autonomic)
CN supplying somatic skeletal muscles
Motor nerve of pharyngeal arch
CN with parasympathetic
actions

16. G
S
E
S
V
E
G
V
E
G
S
A
S
V
A
G
V
A
S
S
A
Development of functional columns in brain stem
Alar plate- sensory column
Senses
• General senses
• Special sense- taste
• Senses from viscera
• Special sense-hearing & Eqb
Pain, touch, temperature, pressure
Taste Sense of distension of viscera
Hearing &
equilibrium

17. Mesencephalic flexure
Cervical flexure
Pontine flexure
Rhombic lip
• Postero-lateral extension of alar plate
of metencephalon.
• Give rise to cerebellum.
Rhombic lip

18. TS of caudal part of Pons
Rhombic lip Cerebellar plate
TS Mesencephalon
Alar plate
Basal plate
Alar plate
Sup colliculus
Inf colliculus
Basal plate
Nuclei of 3rd CN
Nucleus of 4th CN

19. Development of Prosencephalon
Diencephalon
3rd ventricle
Telencephalon
2 lateral ventricles
1. Thalamus
2. Hypothalamus
3. Epithalamus
4. Subthalamus
5. Metathalamus
6. Neurohypophysis

20. Summary
• The CNS develops from a dorsal thickening of ectoderm-the neural
plate, which appears around the middle of the third week.
• The neural plate is induced by the underlying notochord and paraxial
mesoderm to form neural tube.
• The cranial end of the neural tube forms the brain and the remainder
forms the spinal cord.
• The neural canal, the lumen of the neural tube, becomes the
ventricles of the brain and the central canal of the spinal cord.
• Defects in the closure of the neural tube (NTDs) account for most
severe anomalies of nervous system.