Meninges

ANATOMY AIIMS, GROSS ANATOMY, EMBRYOLOGY, NEUROANATOMY, MICROANATOMY, APPLIED/ CLINICAL ANATOMY

The meninges are a crucial set of membranous coverings that envelop both the brain and spinal cord. These protective layers play essential roles in supporting the central nervous system (CNS) and safeguarding it from mechanical damage. Let’s explore the anatomy and functions of the meninges in detail.

Anatomy of the Meninges:

1. Dura Mater:

   • The outermost layer of the meninges.
   • Located directly beneath the bones of the skull and vertebral column.
   • Thick, tough, and inextensible.
   • Consists of two layers:
     • Periosteal layer: Lines the inner surface of the cranial bones.
     • Meningeal layer: Deeper layer continuous with the dura mater of the spinal cord.
   • Contains dural venous sinuses, responsible for venous drainage from the cranium.
   • Receives its own vascular supply primarily from the middle meningeal artery and vein.
   • Innervated by the trigeminal nerve (V1, V2, and V3).
   • Forms several dural reflections that divide the cranial cavity:
     • Falx cerebri: Separates the cerebral hemispheres.
     • Tentorium cerebelli: Separates the occipital lobes from the cerebellum.
     • Falx cerebelli: Separates the cerebellar hemispheres.
     • Diaphragma sellae: Covers the hypophysial fossa of the sphenoid bone.

2. Arachnoid Mater:

   • The middle layer of the meninges.
   • Lies deep to the dura mater.
   • Forms a delicate web-like structure.
   • Contains arachnoid granulations (villi) that allow for CSF reabsorption into the venous sinuses.
   • Subarachnoid space lies between the arachnoid and pia mater.

3. Pia Mater:

   • The innermost layer of the meninges.
   • Adheres closely to the brain and spinal cord surface.
   • Contains blood vessels that supply nutrients to neural tissue.
   • Forms the vascular plexus within the ventricles, contributing to CSF production.

Functions of the Meninges:

1. Supportive Framework:

   • Provides structural support for cerebral and cranial vasculature.
   • Anchors the brain and spinal cord, preventing direct contact with the bony structures.

2. Protection:

   • Acts with cerebrospinal fluid (CSF) to protect the CNS from mechanical damage.
   • Shields against sudden movements, impacts, and pressure changes.

3. Clinical Correlations:

   • Common site of infections (meningitis) and intracranial bleeds.
   • Two types of hematomas involving the dura mater:
     • Extradural hematoma: Arterial blood collects between the skull and periosteal layer of the dura (often due to middle meningeal artery trauma).
     • Subdural hematoma: Venous blood collects between the dura and arachnoid mater.

In summary, the meninges form a protective barrier around the CNS, ensuring its integrity and function. Understanding their anatomy and clinical relevance is essential for healthcare professionals¹²³⁴⁵. 🧠🌟

References:

1. TeachMeAnatomy. The Meninges¹
2. Wikipedia. Meninges²
3. Physiopedia. Meninges³
4. Cleveland Clinic. Meninges: What They Are & Function⁴
5. Kenhub. Meninges of the Brain and Spinal Cord⁵