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 Shape of articulating bones Strength and tension of ligaments Arrangement and tension of muscles Apposition of soft parts 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