271
CHAPTER EIGHT
Joints of the Skeletal System
The ligaments of the shoulder joint, some of which help
prevent displacement of the articulating surfaces, include the
following
(f
g. 8.14)
:
1.
Coracohumeral
(kor
ah-ko-hu
mer-al)
ligament.
This
ligament is composed of a broad band of connective
tissue that connects the coracoid process of the scapula
to the greater tubercle of the humerus. It strengthens the
superior portion of the joint capsule.
2.
Glenohumeral
(gle
no-hu
mer-al)
ligaments.
These
include three bands of F
bers that appear as thickenings
in the ventral wall of the joint capsule. They extend
from the edge of the glenoid cavity to the lesser tubercle
and the anatomical neck of the humerus.
3.
Transverse humeral ligament.
This ligament consists
of a narrow sheet of connective tissue F
bers that runs
between the lesser and the greater tubercles of the
humerus. Together with the intertubercular groove of
the humerus, the ligament forms a canal (retinaculum)
through which the long head of the biceps brachii
muscle passes.
The
glenoid labrum
(gle
noid la
brum) is composed of
F
brocartilage. It is attached along the margin of the glenoid
cavity and forms a rim with a thin, free edge that deepens
the cavity.
Several bursae are associated with the shoulder joint. The
major ones include the
subscapular bursa
between the joint
capsule and the tendon of the subscapularis muscle, the
sub-
deltoid bursa
between the joint capsule and the deep surface
8.6
EXAMPLES OF SYNOVIAL
JOINTS
The shoulder, elbow, hip, and knee are large, freely movable
joints. Although these joints have much in common, each has
a unique structure that makes possible its speciF c function.
Shoulder Joint
The
shoulder joint
is a ball-and-socket joint that consists of
the rounded head of the humerus and the shallow glenoid
cavity of the scapula. The coracoid and acromion processes
of the scapula protect these parts, and dense connective tis-
sue and muscle hold them together.
The joint capsule of the shoulder is attached along the
circumference of the glenoid cavity and the anatomical neck
of the humerus. Although it completely envelops the joint,
the capsule is very loose, and by itself is unable to keep the
bones of the joint in close contact. However, muscles and
tendons surround and reinforce the capsule, keeping together
the articulating parts of the shoulder
(f
g. 8.13)
.
The tendons of several muscles intimately blend with the fibrous
layer of the shoulder joint capsule, forming the
rotator cuff,
which
reinforces and supports the shoulder joint. Throwing a ball can create
powerful decelerating forces that injure the rotator cuF
.
Humerus
Articular cartilage
Scapula
Clavicle
Acromion process
Subdeltoid bursa
Synovial membrane
Joint capsule
Joint cavity
Head of humerus
Joint cavity
Joint capsule
Articular cartilage
Scapula
Humerus
(b)
(a)
FIGURE 8.13
Shoulder joint. (
a
) The shoulder joint allows movements in all directions. A bursa is associated with this joint. (
b
) Photograph of the
shoulder joint (frontal section).
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