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Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics
in 2 minutes or less.
In this installment I will discuss the meninges.
The term meninges comes from the Greek for membrane and refers to 3 membranes that surround
the brain and the spinal cord: the dura mater, the arachnoid mater, and the pia mater.
The meninges protect and provide structural support for the brain as well as contain cerebrospinal
fluid.
The outermost layer of the meninges is the dura mater, which literally means “hard
mother.”
This thick and tough layer adheres to the skull on one side and the arachnoid mater
on the other side.
The dura provides the brain and spinal cord with an extra protective layer, attaches the
brain to the skull and the spinal cord to the vertebral column to keep them from being
jostled around, and provides a system of veinous drainage through which blood can leave the
brain.
The arachnoid mater gets its name because it has the consistency and appearance of a
cobweb.
It is much less substantial than the dura.
Strands of connective tissue called arachnoid trabeculae stretch between the arachnoid and
pia mater.
These help to suspend the brain in place.
Between the arachnoid and pia mater there is also an area known as the subarachnoid
space, which is filled with cerebrospinal fluid.
The pia mater is a thin layer that closely follows the contours of the brain.
It forms a tight membrane around the brain and spinal cord, acting as an an additional
barrier and aiding in the secretion and containment of cerebrospinal fluid.
Blood vessels are held against the pia mater by connective tissue before they penetrate
the brain.
There is a space between the dura of the spinal cord and the bone of the vertebral column
known as the epidural space; analgesics and anesthesia are sometimes administered here.
Also, the dura and arachnoid mater extend several vertebrae below the end of the spinal
cord, creating a cerebrospinal fluid-filled area called the lumbar cistern where there
is no spinal cord present.
Cerebrospinal fluid can be withdrawn from here because a needle can be inserted with
little risk of damaging the spinal cord.
Thus, the lumbar cistern is the site where cerebrospinal fluid is aspirated in a lumbar
puncture, also known as a spinal tap.
This is done, for example, to diagnose meningitis, a potentially life-threatening inflammation
of the meninges.