1. Bone Articulations and Movement
Articulations: Definition
Classification of Joints:
Functional classification
Structural classification
Synovial Joints
Terminology of Movements

2. 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

3. Classification of Articulations
Joints can be classified based on:
- the amount of motion occurring at the joint
- the structure and composition of the joint

4. 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

5. 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)

10. 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)

15. 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.

16. 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

18. 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.

20. 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

21. 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

22. 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.

29. flexion: movement in the anterior/posterior plane that
reduces the angle between articulating bones

31. extension: movement in the same plane that increases the
angle between bones

33. 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!)

34. 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

35. rotation: turning around the longitudinal axis

36. Upper limb:
pronation: rotation of the forearm so that the palm faces posteriorly
- supination: rotation of the forearm so that the palm faces anteriorly

37. 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

38. protraction: moving a structure anterioly
retraction: moving a structure posteriorly

39. elevation: moving a structure superiorly
depression: moving a structure inferiorly

41. Gross Anatomy of Skeletal Muscle
Next Lecture....
The Muscular System:
Gross Anatomy of Skeletal Muscle