Arachnoid membrane

Arachnoid Membrane

The Arachnoid Membrane or Arachnoid Mater is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is situated between the two other meninges, the Pia Mater and the Dura Mater.

Structure

The Arachnoid Membrane is a thin, transparent layer that closely follows the outline of the Dura Mater, but does not enter the convolutions of the brain, unlike the Pia Mater. It is separated from the Dura Mater by the Subdural Space and from the Pia Mater by the Subarachnoid Space, which is filled with Cerebrospinal Fluid.

Function

The primary function of the Arachnoid Membrane, along with the other meninges, is to protect the central nervous system. The Arachnoid Membrane and the Subarachnoid Space also act as a cushion for the brain and spinal cord, providing a shock-absorption effect against physical impacts.

Clinical Significance

Inflammation of the Arachnoid Membrane is known as Arachnoiditis. This can be caused by various factors, including infection, direct injury, or chemical irritation. Symptoms can include numbness, tingling, and a characteristic stinging and burning pain in the lower back or legs.

Arachnoid Cysts are fluid-filled sacs that occur on the Arachnoid Membrane. They are most commonly found in the head, but can also occur around the spinal cord. They are usually asymptomatic, but can cause symptoms if they grow large enough to press on the brain or spinal cord.

Subarachnoid Hemorrhage is a condition where blood leaks into the Subarachnoid Space, often due to a ruptured Aneurysm. This can cause severe headaches, vomiting, loss of consciousness, and can be life-threatening.

See Also

• Meninges
• Central Nervous System
• Cerebrospinal Fluid