|Description:||This photomicrograph revealed some of the normal cytoarchitectural morphology found in a section of meningeal tissue.|
The meninges comprise the three membranes that cover the brain and spinal cord, otherwise know as the structures of the central nervous system. Starting with the innermost meningeal layer nearest the surface of the brain and cord, these layers are arranged in the following order: pia mater, arachnoid membrane, and dura mater.
The outermost meningeal layer, or dura mater, is the thickest, or “toughest” layer, hence its Latin name. It is comprised of dense fibrous connective tissue, and is intimately associated with the inside surface of the overlying cranium.
The dura mater is separated from the innermost pia mater by the arachnoid membrane, which is arranged in what are known as trabeculae, appearing similar to cobwebs, hence, its Latin name. This layer, though quite diaphanous, is leakproof under normal circumstances, keeping the cerebrospinal fluid (CSF) confined to the central nervous system, thereby, protecting the brain against sudden movements.
The innermost meningeal layer is the pia mater, a very delicate layer of connective tissue, which covers all exterior central nervous system structural surfaces. This layer also follows blood vessels into the brain’s interior, and acts as a neuronal sheath for nerve fascicles in the optic nerve, where it is known as perineurium.