281
CHAPTER EIGHT
Joints of the Skeletal System
8.4
TYPES OF SYNOVIAL JOINTS (PAGE 267)
1. Ball-and-socket joints
a. In a ball-and-socket joint, the globular head of a
bone F
ts into the cup-shaped cavity of another
bone.
b. These joints permit a wide variety of movements.
c. The hip and shoulder are ball-and-socket joints.
2. Condylar joints
a. A condylar joint consists of an ovoid condyle of
one bone F
tting into an elliptical cavity of another
bone.
b. This joint permits a variety of movements.
c. The joints between the metacarpals and phalanges
are condylar.
3. Plane joints
a. Articular surfaces of plane joints are nearly fl
at.
b. These joints permit the articular surfaces to slide
back and forth.
c. Most of the joints of the wrist and ankle are plane
joints.
4. Hinge joints
a. In a hinge joint, the convex surface of one bone F
ts
into the concave surface of another bone.
b. This joint permits movement in one plane only.
c. The elbow and the joints of the phalanges are the
hinge type.
5. Pivot joints
a. In a pivot joint, a cylindrical surface of one bone
rotates within a ring of bone and ligament.
b. This joint permits rotational movement.
c. The articulation between the proximal ends of the
radius and the ulna is a pivot joint.
6. Saddle joints
a. A saddle joint forms between bones that have
complementary surfaces with both concave and
convex regions.
b. This joint permits a variety of movements.
c. The articulation between the carpal and
metacarpal of the thumb is a saddle joint.
8.5
TYPES OF JOINT MOVEMENTS
(PAGE 267)
1. Muscles acting at synovial joints produce movements
in different directions and in different planes.
2. Joint movements include fl
exion, extension,
hyperextension, dorsifl
exion, plantar fl
exion,
abduction, adduction, rotation, circumduction,
supination, pronation, eversion, inversion,
protraction, retraction, elevation, and depression.
8.6
EXAMPLES OF SYNOVIAL JOINTS
(PAGE 271)
1. Shoulder joint
a. The shoulder joint is a ball-and-socket joint that
consists of the head of the humerus and the
glenoid cavity of the scapula.
CHAPTER SUMMARY
8.1
INTRODUCTION (PAGE 261)
A joint forms wherever two or more bones meet. Joints
bind parts of the skeleton, allow for bone growth,
permit skeletal parts to change shape during childbirth,
and enable movement in response to skeletal muscle
contractions.
8.2
CLASSIFICATION OF JOINTS (PAGE 261)
Joints are classiF
ed according to the type of tissue that
binds the bones together.
1. ±ibrous joints
a. Bones at F
brous joints are tightly fastened to each
other by a layer of dense connective tissue with
many collagenous F bers.
b. There are three types of F
brous joints.
(1) A syndesmosis has bones bound by long
connective tissue F
bers.
(2) A suture is where fl
at bones are united by
a thin layer of connective tissue and are
interlocked by a set of bony processes.
(3) A gomphosis is formed by the union of a cone-
shaped bony process with a bony socket.
2. Cartilaginous joints
a. A layer of cartilage holds together bones of
cartilaginous joints.
b. There are two types of cartilaginous joints.
(1) A synchondrosis occurs where bones are
united by hyaline cartilage that may disappear
as a result of growth.
(2) A symphysis occurs where articular surfaces
of the bones are covered by hyaline cartilage
and the cartilage is attached to a pad of
F
brocartilage.
3. Synovial joints
a. Synovial joints have a more complex structure than
other types of joints.
b. These joints include articular cartilage, a joint
capsule, and a synovial membrane.
8.3
GENERAL STRUCTURE OF A SYNOVIAL
JOINT (PAGE 263)
1. Articular cartilage covers articular ends of bones in a
synovial joint.
2. A joint capsule strengthened by ligaments holds
bones together.
3. A synovial membrane that secretes synovial fl
uid lines
the inner layer of a joint capsule.
4. Synovial fl
uid moistens, provides nutrients, and
lubricates the articular surfaces.
5. Menisci divide some synovial joints into
compartments.
6. Some synovial joints have fl
uid-F
lled bursae.
a. Bursae are usually located between the skin and
underlying bony prominences.
b. Bursae cushion and aid movement of tendons over
bony parts.
c. Bursae are named according to their locations.
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