The muscles directly associated with the neck and back mainly extend between points on the vertebrae (and ribs) (Fig. 12.11), but some also attach to the skull, the ilium, and, for the psoas group, the femur.

Only a superficial acquaintance with these muscles is required in order to appreciate their functional importance and the suitability of the expaxial division for receiving intramuscular injections. A much more detailed knowledge of the locations, construction, and attachments of the individual units is required for those who may contemplate surgery the vertebral column.

The descriptions that follow supply the basic information, which is most conveniently arranged under the following heads: the expaxial division; the hypaxial division, consisting of distinct cervical and lumbar groupings; and those muscles whose actions are confined to the movements of the head.