1. Histology of the CNS

2. Lecture Objectives
Describe the histology of the cerebral cortex layers.
Describe the histological features of the cerebellum; layers and cells of cerebellar cortex.
Describe the elements of the blood‐brain barrier and the blood‐CSF barrier.
Describe the structure of the choroid plexus and the meninges.

3. The central nervous system
Major parts
Cerebrum
Cerebral cortex
Basal ganglia
Diencephalon
Thalamus
Hypothalamus
Epithalamus
Brainstem
Medulla
Pons
Midbrain
Cerebellum
Spinal cord

4. The central nervous system
Cerebrum, Cerebellum & Spinal cord
Almost no connective tissue therefore a relatively soft, gel‐like organs

5. Cerebral Cortex Cerebral cortex is gray matter overlying white matter
– 2‐4 mm thick containing billions of cells
Has six layers of cells with different forms and sizes

6. Cerebral Cortex Neuronal cells in cortex Pyramidal cells
Efferent fibers
Small – more superficial
Large – Betz cells (motor cells)
Stellate (granule) cells
Star shape
Connect to near neurons
Cells of Martinotti
Axons to superficial layers
Fusiform cells
Spindle shape
Vertical orientation
In deep layers
Horizontal cells of Cajal
Horizontal orientation
In superficial layers
Connect pyramidal cells

7. Cerebral Cortex Layers of cerebral cortex Molecular layer
Area of connection between different cells
Outer granular layer
Small pyramidal & stellate cells
Pyramidal cell layer
Medium size pyramidal cells & martinotti cells
Inner granular layer
Stellate cells
Ganglionic layer
Large pyramidal cells
Multiform cell layer
Mix of different cells

8. Cerebral Cortex I – Molecular layer II – Outer granular layer
III – Pyramidal cell layer
IV – Inner granular layer
V – Ganglionic layer
VI – Multiform cell layer

9. Cerebral Cortex: Pyramidal cells

10. Cerebellum
Content
Cerebellar cortex (folia) & central nuclei are grey matter
Arbor vitae = tree of life = white matter

11. Cerebellum
Cerebellar cortex
White mater (medulla)

12. Cerebellar cortex Three layers Outer molecular layer
Central layer of large Purkinje cells
Inner granule layer

13. Cerebellar cortex Has three layers Outer molecular layer
Few neurons
Mostly unmyelinated fibers
Central layer of large Purkinje cells
One layer of large cells
Inner granule layer
Very small neurons (smallest in the body) that is compactly disposed
– Connect with the afferent fibers

14. Purkinje Cells Purkinje cells has highly developed dendrites
Dendrites occupy most of the molecular layer
Axons traverse the granular layer to the central nuclei of the cerebellum

15. Spinal Cord Anterior median fissure Posterior median sulcus
Gray and white commissures
Central canal
Anterior, posterior & lateral gray horns
Anterior horns contain motor neurons
Posterior horns receive sensory fibers from neurons in the spinal ganglia
Anterior, posterior & lateral white columns

16. Internal Anatomy of Spinal Cord

17. Spinal Cord

18. Spinal Cord

19. Gray matter of spinal cord

20. Central Canal

21. Spinal Cord Gray mater White mater Substantia gelatinosa (entire SC)
Nucleus proprius (entire SC)
Nucleus dorsalis (C8‐L2)
Intermediolateral cell column (T1‐L2, S2‐S4)
Medial motor nucleus (entire SC)
Lateral motor nucleus (enlargements)
White mater
Fasciculus gracilis (entire SC)
Fasciculus cuneatus (C1‐T6)

22. Spinal Cord

23. Spinal Cord

24. Spinal Cord

25. Spinal Cord

28. Meninges Meninges Spaces Dura mater Arachnoid mater Pia mater
Subdural space
Subarachnoid space

29. Meninges Dura mater Arachnoid mater Pia mater
Dense fibroelastic tissue
Lined with a layer of flat cells
Arachnoid mater
Fibrous layer
Lined and covered by flat cells
Fibrous strands connect it to pia mater
Pia mater
Delicate layer
Covered by mesothelial layer

30. Meninges Suparachnoid space Contains blood vessels
When the arteries penetrate the brain tissue it takes with it
Arachnoid mesothelium
Pia mater
Perivascular space
» Continuous with subarachnoid space

31. Blood Brain Barrier protects cells from some toxins and pathogens
proteins & antibiotics can not pass but alcohol & anesthetics do
Structure
tight junctions seal together epithelial cells
continuous basement membrane
astrocyte processes covering capillaries

32. Blood Brain Barrier Areas without BBB Structure
Area postrema in the floor of the fourth ventricle
Areas in the hypothalamus
Structure
Endothelial fenestrations

33. Blood Cerebrospinal Fluid Barrier
Structure
Endothelial cells
BM of endothelial cells
Pale cells
BM of choroidal epithelial cells
Tight junctions seal the choroidal epithelial cells