Histology of the CNS
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.
The central nervous system Major parts Cerebrum Cerebral cortex Basal ganglia Diencephalon Thalamus Hypothalamus Epithalamus Brainstem Medulla Pons Midbrain Cerebellum Spinal cord
The central nervous system Cerebrum, Cerebellum & Spinal cord Almost no connective tissue therefore a relatively soft, gel like organs
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
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 Spindle shape Horizontal orientation In superficial layers Connect pyramidal cells 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 Cerebral Cortex
Cerebral Cortex I Molecular layer II Outer granular layer III Pyramidal cell layer IV Inner granular layer V Ganglionic layer VI Multiform cell layer
Cerebral Cortex: Pyramidal cells
Cerebellum Content Cerebellar cortex (folia) & central nuclei are grey matter Arbor vitae = tree of life = white matter
Cerebellum Cerebellar cortex White mater (medulla)
Three layers Outer molecular layer Central layer of large Purkinje cells Inner granule layer Cerebellar cortex
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
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 Purkinje Cells
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
Internal Anatomy of Spinal Cord
Spinal Cord
Spinal Cord
Gray matter of spinal cord
Central Canal
Gray 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) Spinal Cord
Spinal Cord
Spinal Cord
Spinal Cord
Spinal Cord
Meninges Meninges Dura mater Arachnoid mater Pia mater Spaces Subdural space Subarachnoid space
Dura 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 Meninges
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
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 Blood Brain Barrier
Blood Brain Barrier Areas without BBB Area postrema in the floor of the fourth ventricle Areas in the hypothalamus Structure Endothelial fenestrations
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