273
CHAPTER EIGHT
Joints of the Skeletal System
PRACTICE
13
Which parts help keep together the articulating surfaces of the
shoulder joint?
14
What factors allow an especially wide range of motion in the
shoulder?
15
Which structures form the hinge joint of the elbow?
16
Which parts of the elbow permit pronation and supination of the
hand?
The synovial membrane that forms the inner lining of the
elbow capsule projects into the joint cavity between the radius
and ulna and partially divides the joint into humerus–ulnar
and humerus–radial portions. Also, varying amounts of adi-
pose tissue form fatty pads between the synovial membrane
and the F brous layer of the joint capsule. These pads help pro-
tect nonarticular bony areas during joint movements.
The only movements that can occur at the elbow
between the humerus and ulna are hinge-type movements—
fl exion and extension. The head of the radius, however, is
free to rotate in the anular ligament. This movement allows
pronation and supination of the hand.
(b)
(a)
Humerus
Joint capsule
Synovial
membrane
Joint cavity
Articular cartilage
Coronoid process
Anular
ligament
Radius
Ulna
Olecranon
process
Trochlea
Olecranon process
Radius
Ulna
Humerus
Trochlea
Articular cartilage
Coronoid process
FIGURE 8.15
Elbow joint. (
a
) The elbow joint allows hinge movements, as well as pronation and supination of the hand. (
b
) Photograph of the
elbow joint (sagittal section).
Radius
Tendon of biceps
brachii muscle
Anular ligament
Humerus
Medial
epicondyle
Ulnar collateral ligament
Coronoid process
Ulna
Humerus
Lateral epicondyle
Anular ligament
Radius
Olecranon process
Radial collateral ligament
Ulna
(b)
(a)
FIGURE 8.16
Ligaments associated with the elbow joint. (
a
) The ulnar collateral ligament, medial view, and (
b
) the radial collateral ligament
strengthen the capsular wall of the elbow joint, lateral view.
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