What Are the Meninges?

The meninges are three membranes that cover the brain and spinal cord, protecting the nervous system. The meninges consist of pia mater, the arachnoid membrane and dura mater.

History

The meninges--the singular is "meninx"--were first discovered and named in the Renaissance. Although dissection of cadavers was banned, scientists conducted covert dissections to study the anatomy of the human body. The three layers of material enveloping the brain and spinal cord were identified during this period and given Greek names. "Pia mater" means "soft mother;" "arachnoid" refers to the spider web-like look of the middle layer of membrane and "dura mater," means "tough mother."

Pia mater

Meaning "soft mother," the pia mater is the membrane closest to the brain. It is soft and thin, and covers the brain and spinal cord like a layer of glue, following every curve and contour of the brain. It is impermeable to fluid and laced with a network of small blood vessels called capillaries that supply blood to the brain and spinal cord.

The arachnoid membrane

The web-like arachnoid membrane rests between the pia mater and the dura mater. Unlike the pia mater, the arachnoid membrane covers the brain loosely, a bit like a hairnet. Like the pia mater, it too is impermeable to fluids. The arachnoid membrane also consists of long filaments that attach it to the pia mater. In between the arachnoid membrane and the pia mater is an area called the subarachnoid space, which contains cerebrospinal fluid. Because the arachnoid membrane is impermeable to fluid, it prevents the cerebrospinal fluid--which helps protect the brain from trauma to the skull--from escaping.

Dura mater

Dura mater, or the "tough mother," is the layer of meninges closest to the skull, resting on top of the arachnoid membrane. Attached to the skull in several points, the dura mater is made up of a fibrous material that protects the brain like a tight-fitting cap. Because it is attached to the skull, the dura mater also prevents the brain from moving within the skull.

Conditions and treatments of the meninges

The most commonly known condition that can affect the meninges is meningitis, or the viral or bacterial infection of the meninges. Meningitis causes the meninges to become inflamed. It is usually treated with antibiotics. Bacterial meningitis is considered communicable and can be spread from person to person. The other common condition of the meninges is hematoma, or bleeding in the subarachnoid space or between the dura mater an the arachnoid membrane. Brain hematomas are treated by allowing blood and cerebrospinal fluid to escape through a hole drilled into the skull, relieving the pressure the fluids are putting on the brain.

Resources

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