L1.2.3.1: Meninges

• MENINGES

  • Dura Mater
  • Arachnoid Layer
  • Pia Mater
• ● DURA MATER — “tough or hard mother”

  ○ Leathery outermost layer

  ○ Double-layered covering

  ■ Periosteal layer — attached to the inner surface of the skull

  ■ Meningeal layer — outer covering of the brain; continues as the dura mater of the spinal cord
• ● DURA MATER — “tough or hard mother”

  ○ Dural layers are fused together except in 3 areas where they separate to enclose dural venous sinuses that collect venous blood

  ○ Folds inward in several areas:

  ■ Falx cerebri — separate the 2 cerebral hemispheres

  ■ Tentorium cerebelli — separate the cerebellum from cerebrum
• ● ARACHNOID LAYER

  ○ Arachnida = “spider”

  ○ Weblike extensions span the subarachnoid space to attach it to the pia mater

  ■ Subarachnoid space — filled with cerebrospinal fluid

  ■ Arachnoid granulations — specialized projections of the arachnoid membrane that protrude through the dura mater and absorb cerebrospinal fluid into venous blood
• ● PIA MATER — “gentle mother”

  ○ Internal layer; clings to the surface of the brain and spinal cord following every fold
• Meningitis

  - Inflammation of the meninges

  - Serious threat to the brain because bacterial or viral meningitis may spread into the nervous tissue of the CNS

  - Usually diagnosed by taking a sample of cerebrospinal fluid from the subarachnoid space surrounding the spinal cord

  - Encephalitis: Inflammation of the brain itself