1. The document summarizes the histology of the central nervous system, including the two main cell types (neurons and neuroglia) and their roles. 2. It describes the structure and cell types of several areas of the CNS in detail, including the cerebral cortex, spinal cord, cerebellum, and sensory ganglia. 3. Neurons are the excitable cells that transmit electrical signals, while neuroglia are the supporting cells that surround neurons and help control their chemical environment.

1. Histology
of
Central Nervous System
Dr..Deepak N.Khedekar.
Asst. professor
Dept of Anatomy
LTMMC & GH,MUMBAI
2014

3. Histology of CNS
There are only two functional cell types
1.neurons - excitable nerve cells that transmit
electrical signalsMost neuron cell bodies are
located within the CNS
Nuclei: clusters of neuron cell bodies in the
CNS
Ganglia: clusters of neuron cell bodies in
the Peripheral Nervous System.
2.neuroglia (glial) cells - supporting cells

4. Neurons…

5. Motor neuron
NU N
D
D
A
AH
NB
NB
D
V
A-axon D-dendrite N-nucleus NB-Nissl body
AH-axon hillock V-blood vessel NU-nucleolus

6. Basic types
of neuronal
structure

7. Neuroglia-Supporting cells…
Neuroglia - 4 types in the CNS
Astrocytes
• star shaped with many processes,connect to
neurons; help anchor them to nearby blood
capillaries
• control the chemical environment of the
neurons
Microglia
• oval with thorny projections
• monitor the health of neurons, if infection
occurs, they change into macrophages

8. Neuroglia…

9. Neuroglia …
Ependymal cells :
•shape from squamous to columnar; are ciliated
•line the cavities of the brain and spinal cord
•form a barrier between the neurons and the
rest of the body
Oligodendrocytes :
•have few processes
•line up along neurons and wrap themselves
around axons
•form the myelin sheath

10. Neuroglia…

11. Neuroglia in the Peripheral NS
Satellite cells
• surround neuron cell bodies in the
periphery
• maintain the extracellular environment
Neurolemmocytes (Schwann cells)
• surround axons/dendrites and form the
myelin sheath around larger nerve fibers
• similar to oligodendrocytes in function –
insulators

12. Slide 1.Spinal cord…

13. Spinal cord…

14. Spinal cord-Gray matter
…
Multipolar neurons:
• Vesicular nucleus with distinct nucleolus
• Nissl subastance (basophilic)
Neuroglia :small light staining supportive cells
small basophilic nuclei

15. Spinal cord…

16. Spinal cord- Gray mater…

17. Spinal cord- White matter
Closely packed groups of myelinated axons
Myelin sheaths appear as clear spaces around
dark staining axons

18. Anterior horn of spinal cord

19. Slide 2.Cerebral Cortex
• The grey matter consists of neuron cell bodies
and their dendritic interconnections & glial
cells. The cortex contains 30 billion neurons.
• The evolved cortex in mammals called
neocortex consists of 6 layers of neurons.

20. Cerebral Cortex…
Neocortex
• >90 % of our total cortical area.
• 6 layered structured, Refered to as
homogenic cortex.
Paleocortex
• Covers some parts of the base of the
telencephalon.(olfactory area)
-Forms heterogenic cortex.
Archicortex
• The hippocampal formation.

21. Neuron Cell types
• Two principal cell types are present in neo
cortex. (PSM FuC)
– 1.Pyramidal cell .
– 2.Stellate cell .
• Other cells are …
– 3. Cells of Martinotti
– 4.Fusiform cells
– 5.Horizontal cells of Cajal

22. .
.

23. Pyramidal Cells…
• Pyramid shaped 10 micr.
to 70 micr.).
• Axon arises from the
base and the dendrite
from the apex.
• The largest of the
pyramidal cells are called
the BETZ cells.

24. Functions of pyramidal cells…
• The apical dendrites of pyramidal cells are
studded with dendritic spines.( preferential
site of synaptic contact)
• Most or all pyramidal cells have long axons
that leave the cortex to reach either other
cortical areas or to various subcortical sites.
• Pyramidal cells are the principal output
neurons.

25. Stellate Cells…
Also known as granular cells.
-They are the principal
interneurons of cortex .
--They are typically small (< 10
micrometres) multipolar
neurons.
• principal interneurons

26. Cells Of Martinotti…
• Small polygonal cells.
• Forms synapses with the pyramidal cells.
• Have very few short dendrites.
• axon extends towards the surface and
bifurcate to run horizontally in most
superficial layers.

27. Fusiform Cells…
• Spindle shaped cells, are oriented at right
angles to the cortex.
• Axon arises from the side of the cell body and
passes superficially.
• Dendrites extend from each end of the cell
body branching into deeper and more
superficial layers.
• Functions are similar to that of pyramidal
cells.

28. Horizontal Cells Of Cajal (Or) Retzius
Cajal Cells…
• Small ,spindle shaped, oriented parallel to the
surface.
• Least common cell type, found only in most
superficial layer.
• Axons pass laterally to synapse with dendrites
of pyramidal cells.
• prominent during development, but disappear
after birth.

29. 6 Layers Of Neocortex (MGP-PGM)
1.Plexiform or molecular layer
2.outer granular layer
3.outer pyramidal cell layer
4.inner granular layer
5.inner pyramidal cell layer/ganglion cell layer
6.multiform cell layer
Layers are not equally prominent everywhere.
They form granular & agranular layers.

31. 6 cortical layers …

32. 1.Plexiform layer or molecular layer
• Most superficial layer,
• contains many dendritic and axonal synapses
with one another.
• Sparse nuclei of neuroglia are seen
• Occasional horizontal cells of cajal are seen.
• 2.OUTER GRANULAR LAYER
• Dense population of small pyramidal cells and
stellate cells.
• Different types of neuroglial cells

33. 3.Pyramidal cell layer
• Moderate sized pyramidal cells predominate.
• Large pyramidal cells are present in further
deeper layers.Martinotti cells are also present.
• 4.INNER GRANULAR LAYER
• Consists of densely packed granule cells /stellate
cells
5.GANGLIONIC LAYER
• Large pyramidal cells,Stellate cells (few),Cells of
martinotti
• Huge pyramidal Betz cells of motor cortex are
present. Hence the name ganglion cell layer.

35. Slide 3.Cerebellum…
Gray matter (Cerebellar cortex) consist of 3
layers
Outer molecular layer
middle purkinje layer
Inner granular layer
White matter consist of myelinated nerve
fibers or axons

36. Cerebellum Gray matter(10x)…

37. Cerebellum(40x)…

38. Cerebellum…
Outer molecular layer
• Few, small neurons (basket cells and stellate cells)
• Many fibers extending parallel to length of folium
middle purkinje layer
• Purkinje cells few in no., pyriform in shape,
dendrites in molecular layer
Inner granular layer
• Numerous neurons with prominent nuclei
• Glomeruli-empty spaces in granular layer

40. Cerebellum(40x)…

41. Slide 4.Sensory Ganglia…
• Two types: spinal (dorsal root) and cranial
ganglia associated with spinal and cranial
nerves, respectively
• Contain large sensory neurons and abundant
small glial cells, called satellite cells
• Sensory neurons are pseudounipolar

42. Sensory or Dorsal root ganglia(10x)

43. Dorsal root ganglia…
• Enclosed in irregular CT containing adipose
tissue,nerves,blood vessels.
• Consist of unipolar neurons with eosinophilic
cytoplasm and centrally placed round
nucleus, darkly stained nucleolus
• Cells surrounded by well defined connective
tissue capsule containing numerous satellite
cells (neuroectodermal origin)

44. Sensory or dorsal root ganglion…

45. Sensory or Dorsal root ganglia…

46. Sensory or Dorsal root ganglion…

47. Autonomic-Sympathetic ganglia…

48. Autonomic-Sympathetic ganglia…
• Enclosed in irregular CT containing adipose
tissue,nerves,blood vessels.
• Consist of multipolar neurons with
eosinophilic cytoplasm and ecccentrally
placed round nucleus, darkly stained
nucleolus
• Cells surrounded by ill defined connective
tissue capsule containing few satellite
cells(neuroectodermal origin)

49. Sensory Ganglia vs ANS Ganglia

50. At the end of
the every
lecture…..