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
Classification of Joints
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
Classification of Joints
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)
Classification of Joints
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
Classification of Joints
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
Classification of Joints
Classification of Joints
Functional Classifications
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
Classification of Joints
Classification of Joints
Functional Classifications
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
Intervertebral Articulations
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)
Intervertebral Articulations
Movements of the Vertebral Column Flexion
Bends anteriorly
Extension
Bends posteriorly
Lateral flexion
Bends laterally
Rotation
Turning
Intervertebral Articulations
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
Intervertebral Articulations
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 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 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
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Integration with Other Systems
Fig 9.13 Functional Relationships between the Skeletal System and Other Systems.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Integration with Other Systems
Fig 9.13 Functional Relationships between the Skeletal System and Other Systems.