Simplified Explanation Of The Craniosacral System

Many of my clients have asked me for a simple explanation of the Craniosacral System.

The craniosacral system consists of:

1. The cranium
2. The sacrum and coccyx
3. The meninges
4. Cerebrospinal fluid
5. The structures involved in production and re-uptake of CSF

The word “craniosacral”
comes from the membrane system
that surrounds the central nervous system
and connects the cranium to the sacrum. 

The cranium consists of 22 bones and about 115 or 120 joints, depending on how they formed. This makes a hard-shell that protects the brain and allows for some play in the structure. Those bones are held together by a membrane system.

The meninges are a triple-layered membrane system that surrounds, supports and protects the central nervous system. This membrane system lines the insides of the bones. They provide protective padding and containment of the cerebrospinal fluid in which the central nervous system floats. The dura mater (“tough mother”) forms the outside layer against the bone. The arachnoid (“spider”) is a spongy, cob-web like membrane that adheres to the dura mater. The pia mater (“soft mother”) is a thin layer that lines the surface of the central nervous system. There is room for fluid to flow in the “sub-arachnoid space” between the arachnoid and the pia mater.

The membranes form a dense ring around the big hole where the spine exits the cranium and then form a tube that surrounds the spinal cord. That tube attaches firmly to the second and third vertebrae in the neck and then the second segment of the sacrum.

These membranes also form partitions, called reciprocal tension membranes. The reciprocal tension membranes support the brain and provide a balance of tension for the structure. They are shown here in tan and green. They divide the brain into left and right sections as well as upper and lower sections. It is interesting to note that these membranes are heavily populated with proprioceptors, which feedback information about tension and position.

When the reciprocal tension membranes join to each other and to the lining along the wall of the cranium, they create little channels called venous sinuses. These venous sinuses (shown in blue) are the free-flowing exits for blood and cerebrospinal fluid. They are key in the regulation of intracranial pressure.

Ventricles are balloon-like structures that hold up the neural tissue of the brain so that it floats off the floor of the cranium.

Cerebrospinal fluid is a filtrate of the blood created in the ventricles. It flows out of the ventricles into sub-arachnoid space and returns to the blood via small valves in the venous sinuses.  It floats the delicate central nervous system like a tomato in a jar of water. Cerebrospinal fluid also provides nourishment and transport for waste.

The detail of its architecture and function is truly amazing. This system provides nourishment, protection, pressure regulation, sensory feedback and more.



Tony Preston has a practice in Atlanta, Georgia where he sees clients.

He has written and taught about anatomy, trigger points and cranial therapies since the mid-90s.

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