Chapter 7
The Skeleton
231
7
Radial
notch of
the ulna
Olecranon
Trochlear
notch
Coronoid process
Proximal
radioulnar
joint
Distal
radioulnar
joint
Radial styloid
process
Radius
Neck of
radius
Head of
radius
Ulnar notch
of the radius
Head of ulna
Ulnar styloid
process
Interosseous
membrane
Ulna
Head
Neck
Radial
tuberosity
Radius
Radial styloid
process
(a) Anterior view
(b) Posterior view
(c) Proximal portion of ulna, lateral view
Olecranon
Trochlear notch
Coronoid process
Radial notch
View
(d) Distal ends of the radius and ulna at the wrist
Ulnar notch of radius
Head of
ulna
Ulnar styloid
process
Articulation
for scaphoid
Articulation
for lunate
Radial
styloid
process
View
Figure 7.28
Radius and ulna of the right forearm.
Note the
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
,
Figure 26.)
Forearm
Two parallel long bones, the radius and the ulna, form the
skeleton of the forearm, or
antebrachium
(an
0
te-bra
9
ke-um)
(Figure 7.28)
. 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
ra-
dioulnar joints
(ra
0
de-o-ul
9
nar), and they are connected along
their entire length by a flat, flexible ligament, the
interosseous
membrane
(in
0
ter-os
9
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).
Ulna
±e
ulna
(ul
9
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
olecranon
(elbow)
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