267
CHAPTER EIGHT
Joints of the Skeletal System
8.5
TYPES OF JOINT MOVEMENTS
Skeletal muscle action produces movements at synovial
joints. Typically, one end of a muscle is attached to a rela-
tively immovable or F
xed part on one side of a joint, and
the other end of the muscle is fastened to a movable part on
the other side. When the muscle contracts, its F
bers pull its
movable end (
insertion
) toward its F xed end (
origin
), and a
movement occurs at the joint.
The following terms describe movements at joints that
occur in different directions and in different planes
(f gs.
8.10, 8.11,
and
8.12)
:
exion
(fl
ek
shun) Bending parts at a joint so that
the angle between them decreases and the parts come
closer together (bending the knee).
extension
(ek-sten
shun) Straightening parts at a joint
so that the angle between them increases and the parts
move farther apart (straightening the knee).
hyperextension
(hi
per-ek-sten
shun) Extension of the
parts at a joint beyond the anatomical position (bending
the head back beyond the upright position); often used
and a ligament. Movement at such a joint is limited to
rotation around a central axis. The joint between the
proximal ends of the radius and the ulna, where the head
of the radius rotates in a ring formed by the radial notch
of the ulna and a ligament (anular ligament), is of this
type. Similarly, a pivot joint functions in the neck as the
head turns from side to side. In this case, the ring formed
by a ligament (transverse ligament) and the anterior arch
of the atlas rotates around the dens of the axis (F g. 8.9
e
).
6. A
saddle joint,
or
sellar joint,
forms between bones
whose articulating surfaces have both concave and
convex regions. The surface of one bone F
ts the
complementary surface of the other. This physical
relationship permits a variety of movements, mainly in
two planes, as in the case of the joint between the carpal
(trapezium) and the metacarpal of the thumb (F
g. 8.9
f
).
Table 8.1
summarizes the types of joints.
PRACTICE
9
Name six types of synovial joints.
10
Describe the structure of each type of synovial joint.
TABLE
8.1
|
Types of Joints
Type of Joint
Description
Possible Movements
Example
Fibrous
Articulating bones fastened together by thin layer of dense
connective tissue containing many collagenous ±
bers
1.
Syndesmosis
(amphiarthrotic)
Bones bound by interosseous ligament
Joint ²
exible and may be
twisted
Tibio±
bular articulation
2.
Suture
(synarthrotic)
Flat bones united by sutural ligament
None
Parietal bones articulate at
sagittal suture of skull
3.
Gomphosis
(synarthrotic)
Cone-shaped process fastened in bony socket by periodontal
ligament
None
Root of tooth united with
mandible
Cartilaginous
Articulating bones connected by hyaline cartilage or ±
brocartilage
1.
Synchondrosis
(synarthrotic)
Bones united by bands of hyaline cartilage
None
Joint between epiphysis and
diaphysis of a long bone
2.
Symphysis
(amphiarthrotic)
Articular surfaces separated by thin layers of hyaline cartilage
attached to a pad of ±
brocartilage
Limited movement, as when
the back is bent or twisted
Joints between bodies of
vertebrae
Synovial (diarthrotic)
Articulating ends of bones surrounded by a joint capsule;
articular bone ends covered by hyaline cartilage and separated
by synovial ²
uid
1.
Ball-and-socket
Ball-shaped head of one bone articulates with cup-shaped
socket of another
Movements in all planes,
including rotation
Shoulder, hip
2.
Condylar
Oval-shaped condyle of one bone articulates with elliptical
cavity of another
Variety of movements in
di³
erent planes, but no rotation
Joints between metacarpals
and phalanges
3.
Plane
Articulating surfaces are nearly ²
at or slightly curved
Sliding or twisting
Joints between various
bones of wrist and ankle
4.
Hinge
Convex surface of one bone articulates with concave surface of
another
Flexion and extension
Elbow and joints of
phalanges
5.
Pivot
Cylindrical surface of one bone articulates with ring of bone and
ligament
Rotation
Joint between proximal
ends of radius and ulna
6.
Saddle
Articulating surfaces have both concave and convex regions;
surface of one bone ±
ts the complementary surface of another
Variety of movements, mainly
in two planes
Joint between carpal and
metacarpal of thumb
previous page 297 David Shier Hole's Human Anatomy and Physiology 2010 read online next page 299 David Shier Hole's Human Anatomy and Physiology 2010 read online Home Toggle text on/off