1. Microscopic Anatomy
of Cerebral Cortex
Ibra Cham
USR

2. Objectives
•
Type of cortical cells
•
Layers of cortex
•
Function of the layers

3. Few Demarcations
•
the cerebrum is the principal portion of the brain and contains the cell bodies of
nerves that receive and store sensory information, nerves that control voluntary
motor activity, and nerves that integrate and coordinate the activity of other
nerves, as well as the nerves and neural pathways that constitute memory
•
however, functional part is only the outer 2-5 mm thick layer
•
it has roughly an area of a square meter
•
inhabited by ~100 billion neurons

4. Types of cells in CC
•
Glial cells:
support and protect neurons, and participate in neural activity, neural nutrition,
and defense of cells in the central nervous system
ten times more numerous than neurons
•
Neurons or nerve cells:
form the neuronal functional layers of the cortex: Isocortex (neocortex),
Juxtalocortex (mesocortex) and Allocortex (archicortex)

5. Glial Cells
•
Oligodendrocyte
•
Astrocyte
•
Ependymal cell (VCNS)
•
Microglia
•
Neurolemmocyte (PNS)

6. Oligodendrocyte
•
produce the myelin sheath that
provides the electrical insulation for
neurons
•
mainly white matter

7. Astrocyte
•
structural support, repair processes,
blood-brain barrier, metabolic
exchanges
•
protoplasmic astrocytes (grey matter)
•
fibrous astrocytes (white matter)
•
most numerous

8. Ependymal cell
•
lining cavities of CNS, facilitate
movement and (also likely) absorption
of CSF, providing that they are
provided with cilia for the former
function and long microvilli for the latter
function

9. Microglia
•
constitute the major mechanism of
immune defense in CNS, turn into
phagocytic cells
•
evenly distributed throughout gray and
white matter

10. Nerve Cells
•
Granular (stellate) neurons:
1.
2.
•
dendrites from all sides
axons are within the cortex
Fusiform neurons:
1.
2.
•
deep layers, a large dendrite reaches cortical surface
axons send to cortical areas or beyond
Pyramidal neurons:
1.
2.
axons send to cortical areas or beyond
3.
•
horizontal dendrites, an apical dendrites reaches CS
more abundant than fusiform neurons
These cells contribute to those three layers’ composition (Isocortex ~6L,
Juxtalocortex ~3-6L, and Allocortex ~3L)

11. How many layers do you expect the CC has?

12. The Six Layers of CC
•
(I) The plexiform layer (molecular layer):
fibers parallel to the surface
•
(II) The small pyramidal cell layer (outer granular layer):
small pyramidal cells, and granule cells (stellate cells)
•
(III) The medium pyramidal cells layer (outer pyramidal layer)
larger pyramidal cells

13. The Six Layers of CC –continued
•
(IV) The granular layer (inner granular layer):
small granule cells
•
(V) The large pyramidal cells layer (inner pyramidal layer):
Betz cells (large pyramidal cells)
•
(VI) The layer of polymorphic cells (fusiform/multiform layer):
cells have spindles of fusiform shape

21. Layer I
•
BV, blood vessel
•
Cap, capillary
•
CC, cerebral cortex
•
FC, fusiform cells
•
GC, granule cells
•
NN, neuroglial
nuclei
•
PC, pyramidal cells
•
PM, pia mater
•
V, vein
•
WM, white matter
Layer II
Layer IV
Layer VI
White matter

22. To Mention I-VI Function-wise
•
cortex neurons works in a vertical fashion
•
this makes columns of interconnected neurons working as a unit
•
this neuronal complex extends 30 to 100 micrometer in diameter

23. Pathways of The Signals in Neocortex
•
The layer IV get excited to send signals to the surface area
•
The layers I & II receive signals from lower brain
•
The layers II & III send axons to corresponding areas of the other hemisphere
via (What structure?)
•
The layer V send axons to distal areas e.g. spinal cord
•
The layer VI send axons to thalamus controlling the level of excitation

24. Queries
•
What is the composition of White Matter (the area other than cortex)?
•
What is in the interstitium?

25. References
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Guyton, Ed-12, Ch-47, Pg-576-577, Ch-57, Pg-697-698
•
Junqueira, Ed-12, Ch-9, Pg-140, 147-153
•
Stephen Waxman, Ed-26, Ch-10, Pg-136-138
•
Michael Ross, Ed-6, Ch-12, 382, 394-395
•
Grey’s, Ch-16, Pg-282-286