255 Unit 3B � CNS 1

255 Unit 3B � CNS 1 - Biol 255 Unit 3B Protection of...

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Biol 255 Unit 3B B, Krumhardt, Ph.D., GDCB, ISU 1 Biology 255 Unit 3B Central Nervous System Meninges and the Spinal Cord B. Krumhardt, Ph.D. GDCB, Iowa State University Protection of the CNS Bone, meninges, and cerebrospinal fluid Harmful substances are shielded from the brain by blood-brain barrier Bone Cranium encloses brain Meninges Three connective tissue membranes external to the CNS – dura mater, arachnoid mater, and pia mater • Functions – Cover and protect the CNS – Protect blood vessels and enclose venous sinuses – Contain cerebrospinal fluid (CSF) – Form partitions within skull Dura Mater Leathery composed of two fibrous connective tissue layers around brain (but only one layer around spinal cord) Two layers separate in certain areas and form dural sinuses Dural septa extend to between hemispheres (falx cerebri) and elsewhere - limiting brain movement
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Biol 255 Unit 3B B, Krumhardt, Ph.D., GDCB, ISU 2 Arachnoid Mater Middle layer - forms loose brain covering Separated from dura mater by subdural space Beneath arachnoid - wide subarachnoid space filled with CSF and large blood vessels Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous blood Pia Mater Deepest layer - delicate connective
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