Joints (Articulations) Articulation—site where two or more bones meet Functions of joints: Give...

Joints (Articulations)Joints (Articulations) Articulation—site where two or more bones

Functions of joints: Give skeleton mobility Hold skeleton together

Functional Functional Classification of Joints Classification of Joints

Based on amount of movement allowed by the joint

Three functional classifications: Synarthroses—immovable Amphiarthroses—slightly movable Diarthroses—freely movable

Structural Structural Classification of Joints Classification of Joints

Based on material binding bones together and whether or not a joint cavity is present

Three structural classifications: Fibrous Cartilaginous Synovial

Fibrous JointsFibrous Joints Bones joined by dense fibrous connective

tissue

No joint cavity

Most are synarthrotic (immovable)

Three types: Sutures Syndesmoses Gomphoses

Fibrous Joints: SuturesFibrous Joints: Sutures Rigid, interlocking joints containing short

connective tissue fibers

Allow for growth during youth

In middle age, sutures ossify and are called synostoses

Densefibrousconnectivetissue

Sutureline

(a) Suture

Joint held together with very short,interconnecting fibers, and bone edges

interlock. Found only in the skull.

Fibrous Joints: Fibrous Joints: SyndesmosesSyndesmoses

Bones connected by ligaments (bands of fibrous tissue)

Movement varies from immovable to slightly movable

Examples: Synarthrotic distal tibiofibular joint Diarthrotic interosseous connection between

radius and ulna

Fibula

Ligament

(b) Syndesmosis

Joint held together by a ligament.Fibrous tissue can vary in length, but

is longer than in sutures.

Fibrous Joints: Fibrous Joints: GomphosesGomphoses

Peg-in-socket joints of teeth in alveolar sockets

Fibrous connection is the periodontal ligament

Root oftooth

Socket ofalveolarprocess

Periodontalligament

(c) Gomphosis

“Peg in socket” fibrous joint. Periodontalligament holds tooth in socket.

Cartilaginous JointsCartilaginous Joints Bones united by cartilage

No joint cavity

Two types: Synchondroses Symphyses

Cartilaginous Joints: Cartilaginous Joints: SynchondrosesSynchondroses

A bar or plate of hyaline cartilage unites the bones

All are synarthrotic

Epiphysealplate (temporaryhyaline cartilagejoint)

Sternum(manubrium)

Joint betweenfirst rib andsternum(immovable)

(a) Synchondroses

Bones united by hyaline cartilage

Cartilaginous Joints: Cartilaginous Joints: SymphysesSymphyses

Hyaline cartilage covers the articulating surfaces and is fused to an intervening pad of fibrocartilage

Strong, flexible amphiarthroses

Fibrocartilaginousintervertebraldisc

Pubic symphysis

Body of vertebra

Hyaline cartilage

(b) Symphyses

Bones united by fibrocartilage

Synovial JointsSynovial Joints All are diarthrotic

Include all limb joints; most joints of the body

Synovial JointsSynovial JointsDistinguishing features:

1. Articular cartilage: hyaline cartilage

2. Joint (synovial) cavity: small potential space

3. Articular (joint) capsule: Outer fibrous capsule of dense irregular

connective tissue Inner synovial membrane of loose connective

tissue

4. Synovial fluid: Lubricates and nourishes articular cartilage

Periosteum

Ligament

FibrouscapsuleSynovialmembrane

Joint cavity(containssynovial fluid)

Articular (hyaline)cartilage

Articularcapsule

Synovial JointsSynovial JointsDistinguishing features:

5. Three possible types of reinforcing ligaments:

Capsular (intrinsic)—part of the fibrous capsule

Extracapsular—outside the capsule Intracapsular—deep to capsule; covered by

synovial membrane

6. Rich nerve and blood vessel supply: Nerve fibers detect pain, monitor joint

position and stretch Capillary beds produce filtrate for synovial

Synovial Joints: Synovial Joints: Friction-Reducing Friction-Reducing

StructuresStructures Bursae:

Flattened, fibrous sacs lined with synovial membranes

Contain synovial fluid Commonly act as “ball bearings” where

ligaments, muscles, skin, tendons, or bones rub together

CoracoacromialligamentSubacromialbursa

Cavity inbursa containingsynovial fluidBursa rollsand lessensfriction.Humerus headrolls medially asarm abducts.

(b) Enlargement of (a), showing how a bursaeliminates friction where a ligament (or otherstructure) would rub against a bone

Humerusresting

Humerusmoving

Synovial Joints: Synovial Joints: Friction-Reducing Friction-Reducing

StructuresStructures Tendon sheath:

Elongated bursa that wraps completely around a tendon

Acromionof scapula

Joint cavitycontainingsynovial fluid

Synovialmembrane

Fibrouscapsule

Humerus

Hyalinecartilage

CoracoacromialligamentSubacromialbursa

Fibrousarticular capsuleTendonsheath

Tendon oflong headof bicepsbrachii muscle

(a) Frontal section through the right shoulder joint

Stabilizing Factors at Stabilizing Factors at Synovial JointsSynovial Joints

Shapes of articular surfaces (minor role)

Ligament number and location (limited role)

Muscle tone, which keeps tendons that cross the joint taut Extremely important in reinforcing shoulder

and knee joints and arches of the foot

Synovial Joints: Synovial Joints: MovementMovement

Muscle attachments across a joint: Origin—attachment to the immovable bone Insertion—attachment to the movable bone

Muscle contraction causes the insertion to move toward the origin

Movements occur along transverse, frontal, or sagittal planes

Synovial Joints: Range Synovial Joints: Range of Motionof Motion

Nonaxial—slipping movements only

Uniaxial—movement in one plane

Biaxial—movement in two planes

Multiaxial—movement in or around all three planes

Summary of Summary of Characteristics of Characteristics of

Body JointsBody JointsConsult Table 8.2 (pages 258-259) for:

Joint names Articulating bones Structural classification Functional classification Movements allowed

Movements at Movements at Synovial JointsSynovial Joints

1. Gliding

2. Angular movements: Flexion, extension, hyperextension Abduction, adduction Circumduction

3. Rotation Medial and lateral rotation

Movements at Movements at Synovial JointsSynovial Joints

4. Special movements

Supination, pronation Dorsiflexion, plantar flexion of the foot Inversion, eversion Protraction, retraction Elevation, depression Opposition

Gliding MovementsGliding Movements One flat bone surface glides or slips over

another similar surface

Examples: Intercarpal joints Intertarsal joints Between articular processes of vertebrae

Gliding

(a) Gliding movements at the wrist

Angular MovementsAngular MovementsMovements that occur along the sagittal

plane:

Flexion—decreases the angle of the joint

Extension— increases the angle of the joint

Hyperextension—excessive extension beyond normal range of motion

(b) Angular movements: flexion, extension, and hyperextension of the neck

Hyperextension Extension

Flexion

Hyperextension Flexion

Extension

(c) Angular movements: flexion, extension, andhyperextension of the vertebral column

Extension

Flexion

(d) Angular movements: flexion and extension at theshoulder and knee

Angular MovementsAngular MovementsMovements that occur along the frontal plane:

Abduction—movement away from the midline

Adduction—movement toward the midline

Circumduction—flexion + abduction + extension + adduction of a limb so as to describe a cone in space

Abduction

Adduction

(e) Angular movements: abduction, adduction, andcircumduction of the upper limb at the shoulder

Circumduction

RotationRotation The turning of a bone around its own long

Examples: Between C1 and C2 vertebrae

Rotation of humerus and femur

Lateralrotation

Medialrotation

Rotation

(f) Rotation of the head, neck, and lower limb

Special MovementsSpecial Movements Movements of radius around ulna:

Supination (turning hand backward) Pronation (turning hand forward)

Supination(radius and ulna are parallel)

(a) Pronation (P) and supination (S)

Pronation(radius rotatesover ulna)

Special MovementsSpecial Movements Movements of the foot:

Dorsiflexion (upward movement) Plantar flexion (downward movement)

Dorsiflexion

Plantar flexion

Dorsiflexion

Plantar flexion

(b) Dorsiflexion and plantar flexion

Special MovementsSpecial Movements Movements of the foot:

Inversion (turn sole medially) Eversion (turn sole laterally)

EversionInversion

(c) Inversion and eversion

Special MovementsSpecial Movements Movements in a transverse plane:

Protraction (anterior movement) Retraction (posterior movement)

Protractionof mandible

Retractionof mandible

(d) Protraction and retraction

Special MovementsSpecial Movements Elevation (lifting a body part superiorly)

Depression (moving a body part inferiorly)

Elevationof mandible

Depressionof mandible

(e) Elevation and depression

Special MovementsSpecial Movements Opposition of the thumb

Movement in the saddle joint so that the thumb touches the tips of the other fingers

(f) Opposition

Opposition

Joints (Articulations) Articulation—site where two or more bones meet Functions of joints: Give...

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