--the nerve roots are numbered above the coreesponding verterbrae, so the nerve root that is labelled C5 is beween the C4/C5 vertebrae, the C6 between the C5/C6 bones, the C7 between the C6/C7 bones.

Each nerve root has a specific "dermatome" that it contributes fibers to and that corresponds to a certain region of the body, though there are some individual variations.

Take a look at:

http://www.geriatricsandaging.ca/ga_...atome_fig2.gif

http://images.search.yahoo.com/searc...079ee&ei=UTF-8

http://www.pitt.edu/~regional/Inters.../Dermatome.jpg