Brain Tidbit I Nourishment to the brain Meninges

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 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: CO 2, 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