meninges

 

Protection and Covering of Brain

Cranial menings

The Braun and spinal cord are completely surrounded by 3 layers of tissue called menings.

They lies between skull and brain and between the vertebral foramen and the spinal cord.

The layers which are included in meninges are -

1. Outermost layer  (dura mater)

2. Middle layer (arachnoid mater)

3. Innermost layer (piameter)

Diameter and arachnoid mater are separated by potential space - Subduramater

Arachnoidmater and piamater are separated by subarachnoid space.

Subarachnoid space consist of cerebrospinal fluid (CSF).

1.Duramater

Duramater consist of 2 layers of dense fibrous tissue.

Outer layers of duramater covers the inner surface of skull bone and inner layer provide a protective covering for brain.

Venous blood from brain drains into venous dural sinus between layers of duramater.

Spinal duramater forms a loose sheath around spinal cord.

Duramater extends from the foramen magnum to second sacrum vertebrae. It is attach to foramen magnum by number of fibrous slips.

Nervous entering and leaving the spinal cord passes through these epidural or subdural spaces.

Between inner duramater and arachnoid is potential space called subdural space, filled small amount of serous fluid, not CSF.

2. Arachnoid mater

This is layer of fibrous tissue thlat lie between duramater and piamater.

It is separated from duramater by sub-arachnoid space, filled with CSF, blood vessels.

The arachnoid mater passes over the covering of the brain and accompanies the inner layer of durameter

It continues downward to develop the spinal cord and end by merging with the duramater at the level of 2nd sacral vertebrae.

3. Pia mater

Pia mater is innermost meningeal layer. This is a fine convective tissue containing many blood vessels.

It adhere to brain completely covering it and dipping into each small fissures.

It continues as filum terminale piercing, the arachnoid tube and goes on with the duramater to fuse with coccyx.

Protection of Spinal cord

Bone vertebrae

Meaninges

CSF surround and protect the delicate nervous tissue of spinal cord.

Spinal meninges

Protect three layer of tissue.

Spinal meninges continuous with cranial meninges.

1. Dura mater; outer

2. Arachnoid mater; intermediate

3. Piamater; inner

1. Dura mater; outer

Spinal dura mater is most external of meninges. It extends from foramen magnum to filum terminale.

2. Arachnoid mater; intermediate

Spinal arachnoid mater is located between dura mater and pia mater. They form gap between arachnoid and pia mater called subarachnoid space, this is where CSF is found.

3. Piamater; inner

Spinal piamater is innermost of meninges. It is thin membrane that covers spinal cord, nerve root and their blood vessels. Inferiorly spinal pia mater fuses with filum terminale.