In the name of ALLAH

Joints of the Skeletal System

An articulation (joint) is a point of contact between two or more bones.

Structural classification

• Fibrous : no synovial cavity; bones joined by fibrous connective tissue

• Cartilaginous: no synovial cavity; bones joined by cartilage

• Synovial: synovial cavity present; bones are surrounded by articular capsule and often by accessory ligaments.

Functional Classification

• Synarthroses – immovable

• Amphiarthroses - partially movable

• Diarthroses - freely movable

Fibrous joints

• Suture – thin layer of dense, fibrous connective tissue that joins skull bones.– Sutural ligament– Irregular edges add strength– synarthrosis– Some sutures are replaced by bone as adults:

This is called a synostosis. – Fontanels in children

Fibrous joints cont.

• Gomphosis – cone-shaped peg fits into socket – roots of teeth held in by periodontal ligaments– synarthrosis

Fibrous joints cont.

• Syndesmosis –

• A fibrous joint in which there is more fibrous connective tissue and bones are not held together as tightly as a suture– Forms an interosseous membrane or

ligament

Cartilaginous joints

• Synchondrosis – Synarthrosis– Connecting material is hyaline cartilage– Temporary : epiphyseal plate– Permanent : manubrium and first rib

Cartilaginous joints cont.

• Symphysis– Amphiarthrosis– Disc of fibrocartilage– Intervertebral disks– Pubic symphysis

Synovial Joints : Diarthroses

• Structure:

– Synovial (joint) cavity

– Articular cartilage

– Articular capsule

• Fibrous capsule

–Ligaments

• Synovial membrane

Diarthroses cont.

• Accessory ligaments

– Extracapsular accessory ligaments

– Intracapsular accessory ligaments

• Articular discs (menisci)

– Pads of fibrocartilage

– Maintain stability & fit, ↓ friction

– Torn cartilage

Diarthroses cont.

• Bursae – Saclike structures – Alleviate friction– Lined with synovial membrane– Between skin and bones ; tendons and

bones; ligaments and bones– Bursitis

Factors affecting movement at Diarthroses

1. Shape of articulating bones

2. Strength and tension of ligaments

3. Arrangement and tension of muscles

4. Apposition of soft parts

5. Hormones

Types of Diarthroses

• Gliding (plane) joint

– Articulating surfaces are flat

– Glides back-and-forth and side-to-side

– Rotation is prevented

Hinge joint

• Convex surface of one bone fits into concave surface of another

• Movement is flexion- extension

• Monaxial – in one plane

Pivot joint

• A round or pointed surface of one bone fits into a ring formed by another bone and a ligament

• Rotation

• Monaxial– Medial rotation – anterior surface toward

midline– Lateral rotation – anterior surface away from

midline

Condyloid joint

• An oval-shaped condyle of one bone fits into an elliptical cavity of another bone.

• Flexion-extension

• Adduction-abduction

• Biaxial

• Adduction- movement toward midline

• Abduction – movement away from midline

Ellipsoid joint

Saddle joint

• One bone shaped like a saddle; the other like a rider sitting in the saddle

• Flexion-extension

• Abduction- adduction

• circumduction

• Biaxial

• Allows opposition of thumb

Ball and Socket joint• Ball shaped surface of one bone fits into a

cuplike depression of another

• Flexion-extension

• Abduction-adduction

• Circumduction

• Rotation – movement around longitudinal axis

• Triaxial

Special movements at diarthroses

• Elevation –depression

• Protraction – retraction

• Foot and hand:

– Inversion – eversion

– Dorsiflexion – plantar flexion– Supination – pronation