Lab 1 - Overview of the Nervous System
Meningeal Coverings
Within the cranium and spinal column, the living brain is suspended in a clear liquid called the cerebrospinal fluid (CSF). A continuous sheet composed of three non-neural layers of connective tissue termed meninges (membranes) invests the brain and spinal cord. The meninges consist of the dura mater, arachnoid mater, and pia mater. Together, the pia and arachnoid form the leptomeninges (thin membranes) and are often referred to as a single unit, the pia-arachnoid. The outermost, dura mater (pachymeninx), is composed of two layers: an outer periosteum of the cranium, which contains blood vessels and nerves, and an inner layer of dense fiber tissue. The sinuses of the brain are open cavities between these two layers. Only small pieces of dura remain on the specimens as most of it was removed during the Gross Anatomy course. Folds of dura divide the cranial cavity into components including the falx cerebri between the two hemispheres and the tentorium cerebelli between the occipital lobe and the cerebellum. Because the tentorial edge is so firmly attached to the base of the skull, pathological displacement can result in compression of the brainstem structures.
