B1.19.0 – The Membrane System

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*As with all anatomy I suggest you search for each new term on google then click on the ‘Images’ tab at the top of the page.  Look at as many different pictures of each structure, from as many different angles as you can.  Then look at it on the Visible Body. This will help you get a 3 dimensional image of the structure in your head.

The Membrane System is made up of three layers-

❍ Pia mater This is the innermost layer and it adheres to the surface of the brain and spinal cord.

❍ Arachnoid mater This is the middle layer and is close to the dura.

❍ Dura mater This is the outer most layer and is very tough. It is firmly attached to the bones of the skull, C2, C3, and S2. It is free floating around the rest of the spine.

These three sheaths of membrane are known collectively as the meninges.  They surround and enclose the central nervous system or brain and spinal cord.  The space between each layer is filled with cerebrospinal fluid.  The space between the arachnoid and dura mater is called the Sub arachnoid space. It is the Sub arachnoid space that contains the majority of the cerebrospinal fluid.
The Cranial Dura is further sub-divided into two layers.
The outer layer lines the inside of the cranuim and the inner layer forms several folds or infoldings called –

❍ The Falx Cerebri – A sickle-shaped membrane running from the front the to back of the cranium along the mid line between the two Cerebral hemispheres.

❍ The Falx Cerebelli – A much smaller sickle-shaped membrane passing down the midline of the Occipital region between the two Cerebellar hemispheres.

❍ The Tentorium Cerebelli – A tent-shaped membranous structure passing almost horizontally across the Cranium dividing the Cerebrum above from the Cerebellum below.

❍ The Diaphragma Sellae – A small horizontal membrane forming a roof over the Sella Turcica of the Sphenoid bone and enveloping the Pituitary Gland.

It is helpful to think of the Cranial Dura as being like a balloon with four infoldings inside.  Restrictions in this membrane can pull the cranial bones into compression and restrict areas of the brain.

As stated previously, but it is worth saying again, all parts of the Membrane system are interconnected forming a Reciprocal Tension Membrane System.  Meaning that tensions within any part of the Membrane System are liable to influence all other parts of the Membrane System.

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