Brain Protection – Meninges, CSF, Blood-Brain Barrier

What protects the brain?

• Skull (bone)

• Meninges (membranes)

• Cerebrospinal fluid (CSF)

• Blood-brain barrier (BBB)

What are the three layers of the meninges (from outer to inner)?

• Dura mater (tough, outermost)

• Arachnoid mater (web-like middle layer)

• Pia mater (delicate, clings to brain surface)

Where is CSF found?

In the subarachnoid space (between arachnoid mater and pia mater).

What is cerebrospinal fluid (CSF) and its main functions?

• Formed by choroid plexuses

• Functions: Buoyancy, protection, nutrient delivery, waste removal

Briefly describe CSF flow.

• Made in lateral ventricles → third ventricle → fourth ventricle → subarachnoid space → reabsorbed into superior sagittal sinus via arachnoid granulations.

What happens if CSF doesn't drain properly?

Hydrocephalus (dangerous pressure buildup).

What forms the blood-brain barrier (BBB)?

• Tight junctions between endothelial cells

• Astrocyte feet reinforce it

What can pass through the blood-brain barrier easily?

• Lipid-soluble substances (O₂, CO₂, alcohol)

• Glucose (with transporters)