Download Joints

Joints
Articulating your body
Joints (Articulations)
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Weakest parts of the skeleton
Articulation – site where two or more
bones meet
Functions of joints
Give the skeleton mobility
 Hold the skeleton together
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Classification of Joints:
Structural
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Structural classification
focuses on the material between bones
 Whether or not a joint cavity is present
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The three structural classifications are:
Fibrous
 Cartilaginous
 Synovial
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Classification of Joints:
Functional
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Functional classification is based on the
amount of movement allowed by the
joint
The three functional classes of joints
are:
Synarthroses – immovable
 Amphiarthroses – slightly movable
 Diarthroses – freely movable
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Fibrous Structural Joints
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The bones are joined by fibrous tissues
There is no joint cavity
Most are immovable
There are three types
Sutures
 Syndesmoses
 gomphoses
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Sutures
Figure 8.1a
Sutures
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Occur between the bones of the skull
Comprised of interlocking junctions
completely filled with connective tissue
fibers
Bind bones tightly together, but allow
for growth during youth
In middle age, skull bones fuse and are
called synostoses
Syndesmoses
Figure 8.1b
Syndesmoses
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Bones are connected by a fibrous tissue
ligament
Movement varies from immovable to
slightly variable
Gomphoses
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The peg-in-socket fibrous joint between
a tooth and its alveolar socket
The fibrous connection is the
periodontal ligament
Cartilaginous Joints
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Articulating bones are united by
cartilage
Lack a joint cavity
Two types – synchondroses and
symphyses
Synchondroses
Figure 8.2a, b
Synchondroses
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A bar or plate of hyaline cartilage
unites the bones
All synchondroses are synarthrotic
Symphyses
Figure 8.2c
Symphyses
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Hyaline cartilage covers the articulating
surface of the bone and is fused to an
intervening pad of fibrocartilage
Amphiarthrotic joints designed for
strength and flexibility
Synovial Joints
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Those joints in which the articulating
bones are separated by a fluidcontaining joint cavity
All are freely movable diarthroses
Examples – all limb joints, and most
joints of the body
General Structure
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Synovial joints all have the following
Articular cartilage
 Joint (synovial) cavity
 Articular capsule
 Synovial fluid
 Reinforcing ligaments
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General Structure
Figure 8.3a, b
Friction-Reducing Structures
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Bursae – flattened, fibrous sacs lined
with synovial membranes and containing
synovial fluid
Common where ligaments, muscles, skin,
tendons, or bones rub together
Tendon sheath – elongated bursa that
wraps completely around a tendon
Friction-Reducing Structures
Figure 8.4
Range of Motion
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Nonaxial – slipping movements only
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Uniaxial – movement in one plane
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Biaxial – movement in two planes
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Multiaxial – movement in or around all
three planes
Stability
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Determined by:
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Ligaments
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Articular surfaces
shape determines what movements are possible
unite bones and prevent excessive or undesirable
motion
Muscle tone is accomplished by:
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Muscle tendons across joints acting as stabilizing
factors
Tendons that are kept tight at all times by muscle
tone
Range of Motion
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Nonaxial
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Uniaxial
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movement in one plane
Biaxial
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slipping movements only
movement in two planes
Multiaxial
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movement in or around all three planes
Gliding Movements
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One flat bone surface glides or slips
over another similar surface
Examples – intercarpal and intertarsal
joints, and between the flat articular
processes of the vertebrae
Gliding Movement
Figure 8.5a
Angular Movement
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Flexion
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bending movement that decreases the angle
of the joint
Extension
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reverse of flexion; joint angle is increased
Angular Movement
Figure 8.5b
Knee
Angular Movement
Figure 8.5c, d
Angular Movement
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Dorsiflexion and plantar flexion
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Abduction
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movement away from the midline
Adduction
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up and down movement of the foot
movement toward the midline
Circumduction
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movement describes a cone in space
Angular Movement
Figure 8.5e, f
Rotation
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The turning of a
bone around its
own long axis
Examples
Between first two
vertebrae
 Hip and shoulder
joints
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Figure 8.5g
Special Movements
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Supination and pronation
Inversion and eversion
Protraction and retraction
Elevation and depression
Opposition
Special Movements
Figure 8.6a
Special Movements
Figure 8.6b
Special Movements
Figure 8.6c
Special Movements
Figure 8.6d
Special Movements
Figure 8.6e