(4) Lateral. Away from the midline or lateral side of the body (figure 1-1). In
the forearm, the ulna is medial to the radius and the radius is lateral to the ulna. The
thumb is on the lateral aspect of the hand.
(5) Proximal. Nearest to a point under consideration or the point of origin.
In the case of the extremities, the articulations are considered points of origin (figure
1-2). For instance, the proximal end of the humerus is the upper end.
(6) Distal. Remoteness from a point under consideration or the point of
origin; the opposite of proximal. In the case of the extremities, joints are considered
points of origin (figure 1-2).
Cephalic Toward the head (figure 1-3A).
(10) Caudad. Toward the feet (figure 1-3B).
d. Radiographic Usage of Certain Terms. In diagnostic X-ray services, such
terms as anteroposterior (AP) or posteroanterior (PA) are frequently used. The prefix
indicates the surface from which the central ray (CR) enters the part and the suffix
indicates the surface from which the CR emerges.
e. Planes of the Body (figure 1-4).
(1) Sagittal plane. Any vertical plane that divides the body into right and left
(2) Median or midsagittal plane. The vertical plane that divides the body
into right and left halves.
(3) Frontal or coronal plane. Vertical plane that divides the body into front
and rear portions.
(4) Transverse or horizontal plane. Any horizontal plane that divides the
body into upper and lower portions. The level of this plane must be given.