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Chapter 8 Articulations
Chapter Outline
Module 8.1 Classification of Joints
A. Functional Classification: joints can be classified by how much motion they
allow. Describe the three functional joint classifications.
1. Synarthrosis:
2. Amphiarthrosis:
3. Diarthrosis:
B. Structural Classification: joints can be classified based on their structural
features into the following categories:
1.
joints are fastened together by dense regular collagenous
connective tissue without a joint space between articulating bones. These
joints can be
or
2.
functionally.
joints are fastened together with cartilage without a
joint space. These joints can be
or
functionally.
3.
joints have a layer of hyaline cartilage on the articulating
surface of each bone. The joint space is a fluid-filled cavity found between
articulating bones. These joints are
functionally.
Module 8.2 Structural Classification: Fibrous Joints (Figure 8.1)
A. Describe sutures.
(Figure 8.1a)
B. Describe gomphoses.
(Figure 8.1b)
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C. Describe syndesmoses.
(Figure 8.1c)
Module 8.3 Structural Classification: Cartilaginous Joints (Figure 8.2)
A. Synchondroses: a synchondrosis consists of bones linked together by hyaline
cartilage. The following are examples, which are
functionally
(Figure 8.2a):
1. Epiphyseal plates are composed of
cartilage that connects the
diaphyses and epiphyses of developing long bones, which is replaced with
bone during maturation (Figure 8.2a).
2. First sternocostal and costochondral joints are synchondroses that persists into
adulthood (Figure 8.2b).
B. Symphyses: a symphysis is a joint where the bones are united by a
fibrocartilaginous pad or plug, which is functionally an
.
The following are examples of this type of articulation (Figure 8. 2 b, c, d):
1. The
joints founded between adjacent vertebral bodies
of the spinal column (Figure 8.2c).
2. The
is found between pubic bones of the pelvic
girdle (Figure 8.2d).
Module 8.4 Structural Classification: Synovial Joints (Figures 8.3, 8.4)
A. Structural Elements (Figure 8.3):
1. The joint cavity, or synovial cavity, is a space found between articulating
bones with the following three structural features:
, and
,
.
2. The articular capsule is a double-layered structure that has the following
features (Figure 8.3):
a. The outer fibrous layer keeps the articulating bones from being pulled
apart and isolates the joint from the rest of the body.
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b. The inner layer is called the
membrane that lines the
entire inner surface except where hyaline cartilage is present. What do
the cells in this membrane secrete?
3. Synovial fluid is an thick liquid with the following three main functions:
a.
b.
c.
4. Articular cartilage is composed of a thin layer of hyaline cartilage and
covers all exposed articulating bones within a joint.
a. This thin layer provides a smooth surface for articulating bones to
interact, which reduces wear and tear created by friction.
b. Articular cartilage is avascular, isolated with the capsule. How does
articular cartilage obtain oxygen, nutrients, and remove wastes?
5. Other components of a synovial joint include adipose tissue, nerves, and
blood vessels.
B. Stabilizing and Supporting Factors: synovial joints allow more mobility but are
less stable than the other joint types. The following structures provide additional
stabilization (Figure 8.4):
1. A
is a strand of dense regular collagenous connective
tissue that links one bone to another, which provides additional strength and
reinforcement to a joint.
2. A
is a structural component of skeletal muscle, composed of
dense regular collagenous connective tissue, which connects muscle to bone.
a. Tendons cross joints that they move when muscles are contracted,
which provides stabilization to the joint itself.
b. Muscle tone, a continuous level of muscle contraction, provides a
stabilizing force to the joint.
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3. Bursae and tendon sheaths also provide stabilization forces to the joints
where they are found.
a. A bursa is a synovial-filled fibrous structure that is found in high
stress regions. What is the function of a bursa?
b. A tendon sheath is a long bursa that surrounds tendons in high-stress
regions associated with joints. What do tendon sheaths protect?
C. Arthritis is defined as
of one or more joints that result in pain
and limitations of joint movement. The following are three common types of
arthritis:
1.
is the most common form generally associated with
wear and tear, injuries, and advanced age, which is characterized by pain, joint
stiffness, and lost mobility.
2.
arthritis is associated with joint destruction mediated
by the individual’s own immune system.
3.
arthritis causes joint damage by generating an inflammatory
reaction to uric acid crystal deposits.
Module 8.5 Function of Synovial Joints (Figure 8.5–8.10)
A. Functional Classes of Synovial Joints: bones in a synovial joint move in
different planes around an axis or axes. Describe the motion each of the
following possible different joint configurations allows:
1. Nonaxial joints allow motion
2. Uniaxial joints allow motion
3. Biaxial joints allow motion
4. Multiaxial (triaxial) joints allow motion
B. Movements at Synovial Joints: the following 4 general types of movement can
take place at a synovial joint (Figures 8.5–8.10):
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1. Gliding movements: gliding is a sliding motion between articulating surfaces
that is nonaxial (Figure 8.5).
2. Angular movements increase or decrease the angle between articulating
bones and includes the following specific types of motion (Figures 8.6, 8.7):
a. Flexion decreases the angle between articulating bones by bringing the
bones closer to one another. This movement is paired with
(Figure 8.6).
b. Extension increases the angle between articulating bones, which is the
opposite of
, where articulating bones move away
from one another.
c. Hyperextension is extension beyond anatomical position of the joint.
d. Abduction is the motion of a body part
the
midline of the body or another reference point. This movement is
paired with
(Figure 8.7).
e. Adduction is the motion of a body part
the
midline of the body or another reference point. This movement is the
opposite of
.
f. Circumduction is the only unpaired angular movement where a freely
moveable distal bone moves on a fixed proximal bone in a coneshaped motion. This complex movement is a combination of the two
angular motion pairs:
and
(Figure 8.7e).
3. Rotation is a nonangular motion in which one bone rotates or twists on an
imaginary line running down its middle
axis (Figure
8.8).
4. Special Movements: this group of paired movements includes those types not
otherwise defined by previous categories (Figure 8.9):
a. Opposition and reposition: opposition of the thumb at the 1st
carpometacarpal joint allows the thumb to move across the palmar
surface of the hand.
is the opposite movement that
returns the thumb to its anatomical position (Figure 8.9a, b).
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b. Depression and elevation: depression is the movement of a body part
in an
direction while elevation moves a body part in a
direction (Figure 8.9c, d).
c. Protraction and retraction: protraction moves a body part in an
direction while retraction moves a body part in a
direction (Figure 8.9e, f).
d. Inversion and eversion: inversion is a rotational motion in which the
plantar surface of the foot rotates
toward the midline
of the body. Eversion rotates the foot
away from
the midline (Figure 8.9g, h).
e. Dorsiflexion and plantarflexion: dorsiflexion is a movement where
the angle between the foot and leg
between the foot and leg
. The angle
during plantarflexion
(Figure 8.9i, j).
f. Supination and pronation are rotational movements of the wrist and
ankle regions (Figure 8.10).
C. Range of Motion: the range of motion of a joint is the amount of movement it is
capable of under normal circumstances.
Module 8.6 Types of Synovial Joints (Figures 8.11–8.16)
A. A
joint (gliding joint) is the most simple and least mobile
articulation between the flat surfaces of two bones (Figure 8.11a).
B. In a
joint the convex articular surface of one bone interacts with the
concave depression of a second bone, which allows for movement around a single
axis (uniaxial) (Figure 8.11b).
C. A
joint is a where the rounded end surface of one bone fits into a
groove on the surface of a second bone allowing for movement around one axis
(uniaxial) in which one bone pivots or rotates around the other (Figure 8.11c).
D. A
or ellipsoid joint is a biaxial joint where the oval,
convex surface of one bone fits into a shallow, concave articular surface of a
second bone (Figure 8.11d).
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joint each bone’s articulating surface has both a concave and
E. In a
convex region that allows each bone to fit together allowing for a great deal of
motion for a biaxial joint (Figure 8.11e).
F. A
joint is a multiaxial articulation in which the
articulating surface of one bone is spherical and fits into a cup-shaped depression
in the second bone. This allows for a wide range of motion in around all three
available axes (Figure 8.11f).
G. Specific Hinge Joints: The Elbow and the Knee (Figures 8.13, 8.14)
1. The elbow, a very stable hinge joint, is composed of the following two
articulations and three strong ligaments that support the articular capsule
(Figure 8.13):
a. The humeroulnar joint, the larger of the two joints, is the articulation
between the
of the humerus and the
of the ulna.
b. The humeroradial joint is the articulation between the
of the humerus and the
c. The
of the radius.
ligament (lateral collateral supports the
lateral side of the joint.
d. The
ligament (medial collateral ligament)
supports the medial side of the joint.
e. The
ligament binds the head of the radius to the neck
of the ulna, which stabilizes the radial head in the elbow joint.
2. The knee is a large complex modified hinge articulation composed of two
separate joints, which allows for a small degree rotation and lateral gliding in
addition to flexion and extension. The following are anatomical features
associated with this joint and the patella (Figure 8.14):
a. The articular capsule is absent from the anterior aspect of the joint
where instead it is covered by the patella. This anatomical feature
leaves the knee joint without a single continuous joint cavity.
b. The patella is surrounded by the tendon of the quadriceps femoris
muscle group.
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c. The
ligament, the distal continuation of the
quadriceps tendon, connects the distal patella to the anterior tibia.
d. The
joint is the articulation between the
femoral and tibial condyles.
e. The
joint is the articulation between the
posterior surface of the patella and the anterior patellar surface of the
femur.
f. The medial meniscus and lateral meniscus are c-shaped
fibrocartilaginous pads found femoral and tibial condyles. What
function do these pads serve?
g. The tibial collateral ligament (medial collateral) connects the femur,
medial meniscus, and tibia to one another to provide medial joint
stabilization. What is the function of this ligament?
h. The fibular collateral ligament (lateral collateral) connects the femur
with the fibula. What is the function of this ligament?
i. The anterior cruciate ligament (ACL), found inside the joint cavity,
links the anterior tibia with the posterior femur. What is the function
of this ligament?
j. The posterior cruciate ligament (PCL), also within the joint cavity,
links the posterior tibia with the anterior femur. What is the function
of this ligament?
H. Specific Hinge Joints: The Shoulder and the Hip (Figures 8.15, 8.16)
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1. The shoulder (glenohumeral joint) is a component of the articulations of the
pectoral girdle that connect the upper extremity with the axial skeleton. This
joint is composed of the ball-shaped head of the
glenoid cavity on the lateral
and the
. The shoulder joint has the
following anatomical features (Figure 8.15):
a. The glenoid labrum is a fibrocartilaginous ring that increases the
depth of the glenoid cavity to provide more stability to this multiaxial
joint.
b. The biceps brachii tendon provides a stabilizing force as it passes over
the joint, which helps keep the head of the humerus within the glenoid
cavity.
c. The tendons of the following muscles form the rotator cuff, which
provides most of the joints structural stabilization and strength: the
,
, and
,
.
2. The hip (coxal joint) is a very stable, multiaxial articulation between the
acetabulum and the ball-shaped head of the femur. The hip joint has the
following anatomical features that make it stable enough for its weightbearing responsibilities (Figure 8.16):
a. The acetabular labrum is a fibrocartilaginous ring. What is the
function of the acetabular labrum?
b. Retinacular fibers are intracapsular ligaments that surround the neck of
femur, which reinforce the joint capsule.
c. The iliofemoral ligament is a Y-shaped structure that reinforces
anterior aspect of the external joint capsule.
d. The ischiofemoral ligament is a spiral-shaped structure. What is the
function of this ligament?
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e. The pubofemoral ligament is a triangular-shaped structure. What is
the function of this ligament?
f. The ligament of the head of the femur is a small ligament that
connects the head of the femur with the acetabulum. What is the
function of this ligament?
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