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