The skull is not a single bone, even in an adult, but comprises of 26 individual bones, some of these are paired. In a human body, wherever bones touch each other a joint is formed. All joints exist to allow movement between adjacent bones. In the skull the joints between the skull bones are called sutures and they have a unique structure. An American Osteopath William Garner Sutherland, discovered a specific movement pattern between these bones.
- Membranes known as the dura membrane or meninges surround and attach to the inside of the skull, surround the brain and the spinal cord ( the central nervous system. CNS) attaching again at the sacrum (tail bone).These membranes are filled with Cerebro spinal fluid (CSF) which is produced in the brain, together they form a hydraulic system circulating CSF around the brain and up and down the inside of the spine.
- The skull, spine,dural membranes and CSF provide protection, for the brain and spinal cord
- As cerebrospinal fluid is produced and reabsorbed by the body a rhythmic motion is produced, which in a healthy body is at the rate of approx 6-12 cycles per minute. This is called the craniosacral rhythm.