Lower back

There is an important trigger point in the lower back roughly where two major nerves meet. This can be seen below.  In TCM it is known as YINJIAO CO-7.

Yinjiao means ‘Yin junction’ but is not a meeting place for Yin and Yang energy.  Instead it is described functionally as “the cavity where 'water Qi' meets with 'Fire Qi’”.  Its key role is that “it also intersects with a Thrusting Vessel point and thus provides an alternative means besides CO-1 of accessing Yin energy” .  .

Perhaps key is that it is the point where the craniosacral system starts real ‘water energy’. 

The spinal cord is protected by three layers of tissue  that surround the canal. The dura mater is the outermost layer, and it forms a tough protective coating. The dural sac ends at the vertebral level of the second sacral vertebra, see Sacrum.  But the dura mater doesn’t end when it gets to the skull.  Instead it extends into the skull forming a sort of sack that encloses a number of organs in the brain as well as the spinal cord.   The dura surrounding the brain and the spinal cord is responsible for keeping in the cerebrospinal fluid.