Human Anatomy and Physiology I, Frolich, Meninges, Ventricles, CSF

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)

• 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 water-soluble 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