Chapter 8
Joints of the Skeletal System
Classification of Joints
Joints of the Skeletal System
• 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
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