of the radius
Head of ulna
(a) Anterior view
(b) Posterior view
(c) Proximal portion of ulna, lateral view
(d) Distal ends of the radius and ulna at the wrist
Ulnar notch of radius
Radius and ulna of the right forearm.
structural details of the ulnar head and distal portion of radius and
ulna. (For a related image, see
A Brief Atlas of the Human Body
Two parallel long bones, the radius and the ulna, form the
skeleton of the forearm, or
. Unless a person’s forearm muscles are very
bulky, these bones are easily palpated along their entire length.
±eir proximal ends articulate with the humerus; their distal
ends form joints with bones of the wrist. ±e radius and ulna ar-
ticulate with each other both proximally and distally at small
nar), and they are connected along
their entire length by a ﬂat, ﬂexible ligament, the
e-us; “between the bones”).
In the anatomical position, the radius lies laterally (on the
thumb side) and the ulna medially. However, when you rotate
your forearm so that the palm faces posteriorly (a movement
called pronation), the distal end of the radius crosses over the
ulna and the two bones form an X (see Figure 8.6a, p. 259).
nah; “elbow”) is slightly longer than the radius. It has
the main responsibility for forming the elbow joint with the hu-
merus. Its proximal end looks like the adjustable end of a monkey
wrench: It bears two prominent processes, the