Brain Tidbit I: Nourishment to the brain
• Meninges
•Ventricles
•Cerebro-Spinal Fluid
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
What are meninges?
(review from spinal cord)
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Connective tissues around spinal cord
For protection
For nutrition (CSF)
Three layers
– Pia mater
– Arachnoid mater
– Dura mater
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
Meninges
of the Brain
• 2 dural layers
– Endosteal
– Meningeal
– Form sinuses for blood
drainage
• Arachnoid, pia mater
same as spinal cord
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
Structures of the dura mater in skull
• Falx cerebri
• Falx cerebelli
• Tentorium cerebelli
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
Blood supply to brain
• Carotid, vertebral aa.
• Drain to sinuses formed
by dura mater
• Blood-brain barrier
– Capillary epithelial lining
(endothelium)
impermeable to watersoluble compounds
– Only lipid solubles pass:
CO2, O2, sugars,
ammonia, small
alcohols, lipids like
prostaglandins, steroids
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
Ventricles
(the spaces in your brain…or the USS Enterprise)
• 2 lateral ventricles in
cerebral hemispheres
• Third ventricle in
diencephaln
• Fourth ventricle in
pons/cerebellum/
medulla oblongata
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
Circulation of Cerebrospinal Fluid
• Produced by choroid plexus of
ventricles
• Passes to sub-arachnoid
space of meninges through
roof of fourth ventricle
• Flows down and around spinal
cord
• Diffuses freely into nervous
tissue
• Absorbed out of sub-arachnoid
space and into blood at
arachnoid villi/granulations in
sagittal sinus
• 500 ml/day, turn-over in 8 hrs
• No feedback to choroid
plexus—hydrocephalus is
consequence of flow or
absorption block
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF
CSF Circulation Animation
Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF