Go
to the main content page
Muscles
of the head and neck
The
muscle group of the head and neck is most directly influenced
by the change to an upright posture. This group constitutes
the muscles of the back (nape) and side of the neck. Posture
is not the only influence on these muscles, for the reduction
in the size of the jaws in modern humans also contributes
to the observed muscular differences. Generally, these involve
the reduction in bulk of nuchal (or nape) muscles. In the
upright posture the head is more evenly balanced on the
top of the vertebral column, so less muscle force is needed,
whereas in a pronograde animal with large jaws, the considerable
torque developed at the base of the skull must be resisted
by muscle force. The poise of the human head does pose other
problems, and the detailed attachment and role of some neck
muscles (e.g., sternocleidomastoid) is different in humans
than in the apes.
