an introduction to articulations articulations body movement occurs at joints (articulations)...

An Introduction to Articulations

Articulations

Body movement occurs at joints

(articulations) where two bones connect

Joint Structure

Determines direction and distance of

movement (range of motion)

Joint strength decreases as mobility increases

Classification of Joints

Two methods of classification

Functional classification is based on range

of motion of the joint

Structural classification relies on the

anatomical organization of the joint

Bony, fibrous, cartilaginous or synovial


Functional Classifications Synarthrosis (immovable joint) (e.g., skull suture)

No movement

Bones united by fibrous or cartilaginous connective tissues

May fuse over time

Amphiarthrosis (slightly movable joint) (e.g., b/n tibia and fibula) Little movement

Fibrous or cartilaginous connections

Diarthrosis (freely movable joint) More movement

Also called synovial joints

Subdivided by type of motion


Functional Classifications

Synarthroses (immovable joints) Are very strong

Edges of bones may touch or interlock

Four types of synarthrotic joints:

– Suture (Fibrous joint - e.g., b/n bones of the skull)

– Gomphosis (Fibrous joint - e.g., b/n the teeth and jaws)

– Synchondrosis (Cartilaginous joint - e.g., ephiphyseal

cartilages)

– Synostosis (Bony fusion - e.g., ephiphyseal lines)


Synarthrotic Joints

Suture

Bones interlocked

Are bound by dense fibrous connective tissue

Are found only in skull

Gomphosis

Fibrous connection (periodontal ligament)

Binds teeth to sockets


Synarthrotic Joints Synchondrosis

Is a rigid cartilaginous bridge between two bones:

– epiphyseal cartilage of long bones

– between vertebrosternal ribs and sternum

Synostosis Fused bones, immovable:

– metopic suture of skull

– epiphyseal lines of long bones



Amphiarthroses

More movable than synarthrosis

Stronger than freely movable joint

Two types of amphiarthroses

– syndesmosis:

» bones connected by ligaments

– symphysis:

» bones separated by fibrous cartilage



Synovial joints (diarthroses)

Also called movable joints

At ends of long bones

Within articular capsules

Lined with synovial

membrane

Fig 9-1

Synovial Joints

Components of Synovial Joints

Synovial fluid

Contains slippery proteoglycans secreted by

fibroblasts

Functions of synovial fluid:

– lubrication

– nutrient distribution

– shock absorption

– Protecting articular cartilage

Synovial Joints

Factors That Stabilize Synovial Joints

Prevent injury by limiting range of motion

Collagen fibers (joint capsule, ligaments)

Articulating surfaces and menisci

Other bones, muscles, or fat pads

Tendons of articulating bones

Synovial Joints

Fig 9-1

Synovial Joints

Injuries

Dislocation (luxation)

Articulating surfaces forced out of position

Damages articular cartilage, ligaments, joint

capsule

Subluxation

A partial dislocation

Movements

Types of Dynamic Motion

Linear motion (gliding)

2 surfaces slide past each other ex., b/n carpal or tarsal

bones and clavicle and manubrium

Angular motion

Flexion, Extension, Hyperextension, Circumduction

Rotation

Left, right, medial or internal, lateral or external,

pronation, supination

Movements

Types of Dynamic Motion

Fig 9-2

Movements (Angular)

Fig 9-3

Movements (Angular)

Angular Motion Abduction

Angular motion

Frontal plane

Moves away from longitudinal axis

Adduction Angular motion

Frontal plane

Moves toward longitudinal axis

Fig 9-3

Movements (Angular)

Angular Motion

Circumduction

Circular motion

without rotation

Angular motion

Fig 9-3

Movements (Rotational)

Fig 9-4

Movements

Types of Movements at Synovial Joints Special movements

Inversion:

– twists sole of foot medially or in

Eversion:

– twists sole of foot laterally or out

Dorsiflexion:

– flexion at ankle (lifting toes)

Plantar flexion:

– extension at ankle (pointing toes)

Movements

Special Movements at Synovial Joints Opposition

Thumb movement toward fingers or palm (grasping)

Protraction

Moves anteriorly

In the horizontal plane (pushing forward)

Retraction

Opposite of protraction

Moving anteriorly (pulling back)

Movements

Special Movements at Synovial Joints

Elevation Moves in superior direction (up)

Depression Moves in inferior direction (down)

Lateral flexion Bends vertebral column from side to side

Movements

Fig 9-5

Movements

Classification of Synovial Joints by Shape Gliding – intercarpal articulations/ joints b/n vertebrae

Hinge – ankle, knee, elbow, b/n phalanges

Pivot – C1 and C2 (atlas and axis)/ radio-ulnar joint

Ellipsoid –joints b/n fingers and metacarpal bones/radio-carpal joint

Saddle – straddled joint like the 1st carpometacarpal joint b/n the thumb and underlying trapezium (carpal bone)

Ball-and-socket – shoulder and hip joints

Movements

Fig 9-6

Movements

Ellipsoid Joints Oval articular face within a depression

Motion in two planes (biaxial)

Saddle Joints Two concave, straddled (biaxial)

Ball-and-Socket Joints Round articular face in a depression (triaxial)

Movements

Fig 9-6

Diarthrodial Joints

Type of Joint Movement Example

Hinge Flexion/extension Elbow, Knee

Pivot Rotation Atlas/axis

Ball and socket Flexion/extension Shoulder, HipAbduction/adductionExternal rotationInternal rotationCircumduction

Saddle Flexion/extension Thumb b/n carpals Abduction/adduction and metatarsalsCircumduction

Ellipsoidal Flexion/extension WristAbduction/adduction AnkleCircumduction

Movements

A joint cannot be both mobile and strong

The greater the mobility, the weaker the

joint

Mobile joints are supported by muscles

and ligaments, not bone-to-bone

connections

Intervertebral Articulations

Fig 9-7


Vertebral Joints

Also called symphyseal joints

As vertebral column moves

Nucleus pulposus shifts

Disc shape conforms to motion

Intervertebral Ligaments

Bind vertebrae together

Stabilize the vertebral column

Intervertebral Articulations Six Intervertebral Ligaments

Anterior longitudinal ligament

Connects anterior bodies

Posterior longitudinal ligament

Connects posterior bodies

Ligamentum flavum

Connects laminae

Interspinous ligament

Connects spinous processes

Supraspinous ligament

Connects tips of spinous processes (C7 to sacrum)

Ligamentum nuchae

Continues supraspinous ligament (C7 to skull)


Movements of the Vertebral Column Flexion

Bends anteriorly

Extension

Bends posteriorly

Lateral flexion

Bends laterally

Rotation

Turning


Damage to Intervertebral Discs

Slipped disc

Bulge in anulus fibrosus

Invades vertebral canal

Herniated disc

Nucleus pulposus breaks through anulus fibrosus

Presses on spinal cord or nerves


Herniated disc is caused by a protrusion of the nucleus pulposus. Fig 9-8

The Shoulder Joint

Also called the glenohumeral joint

Allows more motion than any other joint

Is the least stable

Supported by skeletal muscles, tendons, ligaments

Ball-and-socket diarthrosis (freely moveable joint)

Between head of humerus and glenoid cavity of

scapula

The Shoulder Joint

Socket of the Shoulder Joint

Glenoid labrum

Deepens socket of glenoid cavity

Fibrous cartilage lining

Extends past the bone

Processes of the Shoulder Joint

Acromion (clavicle) and coracoid process (scapula)

Project laterally, superior to the humerus

Help stabilize the joint

The Shoulder Joint

Shoulder Ligaments

Glenohumeral

Coracohumeral

Coraco-acromial

Coracoclavicular

Acromioclavicular

Shoulder Separation

Dislocation of the shoulder joint

The Shoulder Joint

Shoulder Muscles (also called rotator cuff) Supraspinatus Infraspinatus Subscapularis Teres minor

Shoulder Bursae Subacromial Subcoracoid Subdeltoid Subscapular

The Shoulder Joint

Fig 9-9

The Elbow Joint A stable hinge joint

With articulations involving humerus, radius, and ulna

Articulations of the Elbow

Humero-ulnar joint

Largest and strongest articulation at the elbow

Trochlea of humerus and trochlear notch of ulna

Limited movement

Humeroradial joint:

Smaller articulation

Capitulum of humerus and head of radius

The Elbow Joint

Fig 9-10

The Elbow Joint

Supporting Structures of

the Elbow Biceps brachii muscle

Attached to radial tuberosity

Controls elbow motion

Elbow Ligaments Radial collateral

Annular

Ulnar collateral

Fig 9-10

The Hip Joint

Also called coxal joint

Strong ball-and-socket diarthrosis

Wide range of motion

Factors that increase stability:

Strong muscular padding

Tough capsule

Almost complete bony socket

Supporting ligaments

The Hip Joint

Structures of the Hip Joint Head of femur fits into it

Socket of acetabulum

Which is extended by fibrocartilaginous acetabular labrum

Ligaments of the Hip Joint Iliofemoral

Pubofemoral

Ischiofemoral

Transverse acetabular

Ligamentum teres

The Hip Joint

Fig 9-11

The Knee Joint

A complicated hinge joint

Transfers weight from femur to tibia

Articulations of the knee joint

Two femur–tibia articulations

At medial and lateral condyles

One between patella and patellar surface of femur

The Knee Joint

Menisci of the Knee Medial and lateral menisci

Fibrous cartilage pads

At femur–tibia articulations

Cushion and stabilize joint

Give lateral support

Locking knees Standing with legs straight:

– “locks” knees by jamming lateral meniscus between tibia and femur

The Knee Joint

Seven Ligaments of the Knee Joint

Patellar ligament (anterior)

Two popliteal ligaments (posterior)

Anterior and posterior cruciate ligaments (inside joint

capsule)

Tibial collateral ligament (medial)

Fibular collateral ligament (lateral)

The Knee Joint

Fig 9-12

Aging

Rheumatism A pain and stiffness of skeletal and muscular

systems Arthritis

All forms of rheumatism that damage articular cartilages of synovial joints

Osteoarthritis Caused by wear and tear of joint surfaces, or

genetic factors affecting collagen formation Generally in people over age 60

Aging

Rheumatoid Arthritis An inflammatory condition Caused by infection, allergy, or autoimmune

disease Involves the immune system

Gouty Arthritis Occurs when crystals (uric acid or calcium

salts) Form within synovial fluid Due to metabolic disorders

Aging

Joint Immobilization Reduces flow of synovial fluid Can cause arthritis symptoms Treated by continuous passive motion

(therapy) Bones and Aging

Bone mass decreases Bones weaken Increases risk of hip fracture, hip dislocation,

or pelvic fracture

Integration with Other Systems

Factors Affecting Bone Strength Age

Physical stress

Hormone levels

Calcium and phosphorus uptake and excretion

Genetic and environmental factors

an introduction to articulations articulations body movement occurs at joints (articulations)...

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