Cranial Pia Mater

Structure and/or Key Features

There are three layers that make up the meninges, the dura, arachnoid, and pia mater. The meningeal layers can also be divided according to the stage of their development, including the leptomeninges (arachnoid and pia mater) and pachymeninx (dura mater).

The pia mater is the innermost of the three meningeal layers that are present around the brain and spinal cord. The meninges, as well as the cerebrospinal fluid encircle and protect the central nervous system.

The pia mater is a fine, transparent, shiny, vascularized membrane. It appears to be tightly adhered to the cerebral surface, including all gyri and sulci, and cannot be dissected away. It is separated from the brain surface by a subpial space, which cannot be seen with the naked eye. The pia mater also closely surrounds the spinal cord, including the roots of the spinal nerves and the spinal blood vessels.

The pia mater and the arachnoid mater have similar structures as they share an embryological origin. Together, the pia and arachnoid make up the leptomeninges.

Anatomical Relations

The pia mater forms the innermost layer of the meninges and is situated between the subarachnoid space and the subpial space. The cerebrospinal fluid can be found in the subarachnoid space.

Function

The principal function of meningeal layers is to protect and provide support to the central nervous system. The pia mater plays a regulatory role in the central nervous system as it is concerned with the blood-brain barrier. More specifically, the pia mater serves as a regulatory gateway between the subarachnoid space and the brain.

Clinical Correlates

—Bacterial meningitis

—Viral meningitis

References

Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.