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Chapter 8
Joints of the Skeletal System
Classification of Joints
Joints of the Skeletal System
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Articulations
Functional junctions between bones
Bind parts of skeletal system together
Make bone growth possible
Permit parts of the skeleton to change shape
during childbirth
• Enable body to move in response to skeletal
muscle contraction
Functional Classification Of Joints
• Classification=based on the amount of
movement allowed
• 3 types:
• Synarthroses = immovable joints
– Example = sutures of skull
• Amphiarthroses = slightly movable joints.
– Example = intervertebral discs between vertebrae
• Diarthroses = freely movable joints
– Examples = joints of appendicular skeleton
Structural Classification Of Joints
• Classification= Based on material, which joins
bones
• 3 types:
– Fibrous
– Cartilaginous
– Synovial
Fibrous Joints
• joints composed of fibrous tissue
• no joint cavity is present
• 3 types:
– Syndesmosis
– Suture
– Gomphosis
Fibrous Joints cont.
• Syndesmosis = cord
of fibrous tissue
called a ligament
– amphiarthroses with
"give" but no true
movement
– Example = distal
tibiofibular joint
Fibrous Joints cont.
• Sutures = short
fibrous CT fibers
– synarthroses
– Only found in skull
Fibrous Joints cont.
• Gomphosis = tooth
within its bony socket
(alveolar fossa)
– short periodontal
ligament
Cartilaginous Joints
• joints composed of cartilage
• no joint cavity
• 2 types:
– Synchondrosis
– Symphysis
Cartilaginous Joints cont.
• Synchondrosis = a
plate of hyaline
cartilage
– sites of bone growth
during youth
– eventually ossify =
synarthrotic
– Examples: joint
between the first rib
and manubrium and
the epiphyseal plate
Cartilaginous Joints cont.
• Symphysis = pad or
plate of fibrocartilage
– compressible "shock
absorber"
– limited movement =
amphiarthroses
– Examples:
intervertebral discs
and symphysis pubis
Synovial Joints
• = fluid-filled joint
cavity
– free movement
= diarthrosis
General Structure Of A Synovial Joint
• General Structure Of A Synovial Joint = 5
distinct features:
1. Articular cartilage = hyaline cartilage
covers the surface of each bone
2. Joint cavity = a potential space between the
two bones, filled with synovial fluid
3. Synovial fluid = viscous lubricating fluid
within cavity
– reduces friction between cartilages of 2 bones
• provide lubrication
• nourish cartilage
• contain phagocytes
Synovial Joints cont.
4. Articular capsule = double layered capsule
surrounding cavity:
– External, tough flexible fibrous capsule
(continuous with periosteum of the bones)
– Synovial membrane = loose CT lining of fibrous
capsule, that also covers all internal joint surfaces
excluding hyaline cartilage
5. Reinforcing ligaments = ligaments that
strengthen joint
– Definition: A ligament joins a bone to another
bone across a synovial joint
– usually thickened portions of fibrous capsule
(intrinsic or capsular)
General Structure of a Synovial Joint
Synovial Joints cont.
• Other joint features:
• fatty pads (hip & knee)
• menisci or articular discs or that separate
cavity into 2 compartments (knee, jaw,
sternoclavicular)
Synovial Joints cont.
• bursa = flattened fibrous sacs with a synovial
membrane and fluid that act as "ball bearings"
to prevent friction on adjacent structures
during joint activity
– cushion the movement of one body part over
another;
– located between skin and bone (where skin rubs
over bone), and between muscle, tendons,
ligaments and bone.
Types Of Synovial Joints
• Ball-and-socket joints
= most freely movable
joints; all angular
movement
– The head of one bone fits
into the socket of another
– Examples = hip and
shoulder
• Condyloid joints =
permit all angular
motion, except rotation
– Examples = wrists and
knuckles
Types Of Synovial Joints cont.
• Gliding joints =
cartilaginous joints
– Example =
intervertebral discs
• Hinge joints =
permit flexion &
extension only
– Examples = elbow
and knee
Types Of Synovial Joints cont.
• Pivot joints = permit
rotation
– Example = first
intervertebral joint
(atlantoaxial joint)
• Saddle joints =
thumb
Types Of Joint Movements
Introduction
• Origin = part of muscle attached to the
immovable bone
• Insertion = part of a muscle attached to the
movable bone
• When a muscle contracts across a joint, its
insertion is pulled toward its origin
Three general types of movement
Gliding movements = when flat bone surfaces
glide or slide over one another
– occur at cartilaginous joints
– Examples = intervertebral discs and
sternoclavicular joints
Angular movements = changes in angles
between bones
– occur only at synovial joints
Movement cont.
• Flexion = decreasing the angle between 2
bones.
– Example = head toward chest
– Dorsiflexion = bringing foot closer to shin
– Plantar flexion = pointing one's toe (flexion
toward the sole)
• Extension = increasing the angle between 2
bones
– Example = straightening a flexed neck
– Hyperextension = increasing the angle greater
than 180o
Movement cont.
• Abduction = moving a limb away from the
midline.
– Example = raising arm or thigh laterally;
• Adduction = moving a limb toward the
midline
Movement cont.
• Circumduction = moving a limb in a circular
(cone-shaped) manner
• Rotation = turning movement of a bone along
its long axis.
– Example = atlas over axis (i.e. “just say no”)
– Example = shoulder and hip joint
Special Movements
Special Movements = those at specific joints
• supination/pronation = movements between
the radius and ulna at the proximal radioulnar
joint
– thumb up = supination
– thumb down = pronation
• inversion/eversion = movement of foot
– sole inward = inversion
– sole out = eversion
Special Movements cont.
• elevation/depression
– shoulder shrug = elevation
– mandible in opening mouth = depression
• protraction/retraction
– thrust forward = protraction
– pull back = retraction
Shoulder joint
• Shoulder joint (2 joints)
• Ball and socket is the glenohumeral joint
– joins Glenoid cavity and head of humerus
• Syndesmosis is called the acromioclavicular joint
– acromial end of clavicle and the acromion process of the
scapula
• Ball and socket is surrounded by many reinforcing
ligaments and tendons collectively called the rotator
cuff
• Many bursa also lubricate the shoulder
• Movement can occur in any angular plane
Elbow joint
• (2 joints)
• Hinge is between trochlea of humerus and
trochlear notch of ulna
• Gliding joint is between capitulum of
humerus and head of radius
• Very stable joint with many reinforcing
ligaments
• Only allows flexion and extension
Hip joint
• (coxal joint)
• Ball and socket between head of femur and
acetabulum of coxa
• Contains many large reinforcing ligaments
• Allows same movements as shoulder, but with
less range due to bony limitations
Knee
• (3 joints)
• Largest, most complex joint
– Functions as a hinge even though 3 joints work
together
• Medial condyles of femur and tibia make one
condyloid joint
• Lateral condyles of femur and tibia make
another condyloid joint
• Patellar surface of femur and patella make a
gliding joint
– Flexion and extension with some slight rotation
– Contains many reinforcing structures
Knee cont.
• Menisci
– medial meniscus
– lateral meniscus
• C-shaped fibrocartilage pads
– Reshape the tibial condyles for a better fit
– Absorb shock
– Many bursae