266
UNIT TWO
joints and the joints formed by ribs 2 through 7
connecting with the sternum are also plane joints.
4. In a
hinge joint,
the convex surface of one bone F
ts into
the concave surface of another, as in the elbow and the
joints of the phalanges. Such a joint resembles the hinge
of a door in that it permits movement in one plane only
(F
g. 8.9
d
).
5. In a
pivot joint,
or
trochoid joint,
the cylindrical
surface of one bone rotates in a ring formed of bone
and phalanges. This type of joint permits a variety of
movements in different planes; rotational movement,
however, is not possible (F
g. 8.9
b
).
3. The articulating surfaces of
plane joints,
or
gliding
joints,
are nearly fl
at or slightly curved. These joints
allow sliding or back-and-forth motion and twisting
movements. Most of the joints in the wrist and ankle,
as well as those between the articular processes of
vertebrae, belong to this group (F
g. 8.9
c
). The sacroiliac
Hip bone
Metacarpal
Phalanx
(a)
Ball-and-socket joint
(c)
Plane joint
(e)
Pivot joint
(d)
Hinge joint
(b)
Condylar joint
Head of femur
in acetabulum
Femur
Carpals
(f)
Saddle joint
First
metacarpal
Trapezium
Humerus
Dens
Transverse
ligament
Ulna
Radius
Atlas
Axis
FIGURE 8.9
Types and examples of synovial (freely movable) joints.
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