Bone Articulations and Movement Articulations: Definition Classification of Joints: Functional...
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Transcript of Bone Articulations and Movement Articulations: Definition Classification of Joints: Functional...
Bone Articulations and Movement
Articulations: Definition
Classification of Joints:
Functional classification
Structural classification
Synovial Joints
Terminology of Movements
Articulations
Articulations (or joints) are places where two or more bones meet- required if motion is to occur
- structure and function are interrelated
- each articulation balances the need for stability versus the need for mobility
Classification of Articulations
Joints can be classified based on:
- the amount of motion occurring at the joint
- the structure and composition of the joint
Classification of Articulations by Function
The classification of joints by function (amount of movement) is as follows:- Synarthroses: little or no movement in the joint (extremely strong joint)example: sutures between bones of the skull- Amphiarthrosis: slightly movable joint (strong, yet slightly mobile joint) example: pubic symphysis, intervertebral discs- Diarthrosis: freely movable joint (weakest type)examples: shoulder, elbow, hip, knee joints
Classification of Articulations by Structure
There are three types of joints classified by structure: fibrous, cartilagenous, and synovial joints.
Fibrous joints - joints in which bones are held together by fibrous CT- sutures: between bones of the skull- synostosis: two bones grow across joint to form a single bone (fusion of two frontal bones)- syndesmosis: gap between bones wider than in suture (interosseus membrane of radio-ulnar joint)- gomphoses: joints in which one end fits into socket of other bone (teeth held in alveoli by periodontal ligaments; fig 24.6)
Cartilagenous Joints
Joints in which bones are united by hyaline of fibrocartilage.
- synchondroses: cartilagenous joint in which the bones are joined by hyaline cartilage (example: costal cartilage to sternum)
- symphysis: cartilagenous joint in which the bones are joined by fibrous cartilage (example: symphysis pubis, intervertebral discs)
Synovial Joints
Synovial joints are those that have a joint cavity containing synovial fluid.
Since there is a lot of movement in diarthrotic joints, you need:
- extra space between bones
- a lubricating fluid to reduce friction.
Synovial joints are usually found at the ends of long bones.
Structure of Synovial Joints
Features of synovial joints:- enclosed in a joint capsule (outer: fibrous capsule, inner: synovial membrane)- the synovial membrane secretes synovial fluid- the ends of bone are covered by articular cartilage (hyaline)- movement can be mono-axial, biaxial, or multiaxial
Bursae
In some joints, the synovial membrane may extend outside the joint itself as a pocket, or bursa.
A bursa provides protection between bone and tendons, or between skin and bone.
Types of Synovial Joints
Synovial joints can be classified based on the shapes of the adjoining articular surfaces:
gliding: manubrio-clavicular joint (monoaxial: one plane)
hinge: monoaxial (elbow), convex cylinder of one bone into a concavity of another bone
Types of Synovial Joints
Pivot: monoaxial, rotation around a single axis
Saddle joint: two saddle-shaped articular surfaces at right angles to each other; biaxial
Types of Synovial Joints
Ball and socket: ball (head) of one bone into socket of adjacent bone; multiaxial
Condyloid (ellipsoid): like a ball and socket, except ball is more oval; biaxial.
flexion: movement in the anterior/posterior plane that
reduces the angle between articulating bones
extension: movement in the same plane that increases the
angle between bones
-plantarflexion: movement of the foot toward the plantar surface -(standing on toes)
- dorsiflexion: movement of the foot toward the the shin
(note that this is really extension of the foot!)
abduction: moving away from the longitudinal axis of
the body in the frontal plane (moving back is adduction)
circumduction: combination of flexion, extension, abduction,
and adduction that moves the limb in a cone
rotation: turning around the longitudinal axis
Upper limb:-pronation: rotation of the forearm so that the palm faces posteriorly
- supination: rotation of the forearm so that the palm faces anteriorly
Lower limb:
- inversion: turning the ankle so that the plantar surface (sole) faces medially
-eversion: turning the ankle so that the plantar surface faces
laterally
protraction: moving a structure anterioly
retraction: moving a structure posteriorly
elevation: moving a structure superiorly
depression: moving a structure inferiorly
Next Lecture....
The Muscular System:
Gross Anatomy of Skeletal Muscle