Structure:
Positions of the parts of the axial and appendicular skeleton,
and their parts, define the relation of of one to another. Each part is
in some position, compared to the position of a connected part. The anatomy
determines the capability for assuming a position. For example, animals
with vertebra between the head and the trunk have a neck that allows moving
the position of the head, either forward, backward or to either side, in
relation to the trunk.
Function:
Movements that close joints produce flexion, and those that straighten
joints produce extension. Turning the trunk or an extremity so that the
back is toward the observer, is called pronation, and turning so the front
is toward the observer, indicates supination. Movement of a part toward
the body is adduction, and movement away, is abduction. By pulling from
an anchoring bone, muscles change the position
of the moving bone across a joint. A muscle has its orgin on the anchoring
bone, and its insertion on the moving bone. Many bones and muscles may
cooperate for producing a position, or a motion. Muscles are often named
with a label that indicates its action, eg., abductor, pronator, etc.
