Chapter 9: Articulations A

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Chapter 9ArticulationsAP Biology 141
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Articulations

• Body movement occurs at joints (articulations)
  where 2 bones connect
• Joint Structure
• Determines direction and distance of movement
  (range of motion)
• Joint strength decreases as mobility increases

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What are the major categories of joints, and the
structure and function of each category?
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Functional Classification
Table 91
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Functional Classifications

• Synarthrosis
• no movement
• Amphiarthrosis
• little movement
• Diarthrosis
• more movement

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Synarthroses

• Also called immovable joints
• Fibrous or cartilaginous connections
• May fuse over time
• Amphiarthroses
• Also called slightly moveable joints
• Fibrous or cartilaginous connections

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Diarthroses

• Synovial joints
• Also called freely moveable joints
• Subdivided by type of motion

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Structural Classification
Table 92
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Structural Classifications

• Bony
• Fibrous
• Cartilaginous
• Synovial

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Synarthroses (Immovable Joints)

• Are very strong
• Edges of bones may touch or interlock
• 4 Types of Synarthrotic Joints
• Suture
• Gomphosis
• Synchondrosis
• Synostosis

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Suture

• Bones interlocked
• Are bound by dense fibrous connective tissue
• Are found only in skull
• Gomphosis
• Fibrous connection (periodontal ligament)
• Binds teeth to sockets

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Synchondrosis

• Is a rigid cartilaginous bridge between 2 bones
• epiphyseal cartilage of long bones
• between vertebrosternal ribs and sternum
• Synostosis
• Fused bones, immovable
• metopic suture of skull
• epiphyseal lines of long bones

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Amphiarthroses

• More moveable than synarthrosis
• Stronger than freely movable joint
• 2 Types of Amphiarthroses
• Syndesmosis
• bones connected by ligaments
• Symphysis
• bones separated by fibrocartilage

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What is the basic structure of a synovial joint,
and what are the common accessory structures and
their functions?
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Synovial Joints (Diarthroses)

• Also called moveable joints
• At ends of long bones
• Within articular capsules
• Lined with synovial membrane

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Articular Cartilages

• Pad articulating surfaces within articular
  capsules
• prevent bones from touching
• Smooth surfaces lubricated by synovial fluid
• reduce friction

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Synovial Fluid

• Contains slippery proteoglycans secreted by
  fibroblasts
• Functions of Synovial Fluid
• Lubrication
• Nutrient distribution
• Shock absorption

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Synovial Joints Accessory Structures

• Cartilages
• Cushion the joint
• fibrocartilage meniscus (articular disc)
• Fat pads
• Cushion the joint
• fibrocartilage meniscus (articular disc)
• Accessory Ligaments
• Support, strengthen joints
• Sprain
• ligaments with torn collagen fibers

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Synovial Joints Accessory Structures

• Tendons
• Attach to muscles around joint
• Help support joint
• Bursae
• Pockets of synovial fluid
• Cushion areas where tendons or ligaments rub

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Synovial Joints Stabilizing Factors

• 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

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Injuries

• Dislocation (luxation)
• articulating surfaces forced out of position
• damages articular cartilage, ligaments, joint
  capsule
• Subluxation
• a partial dislocation

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What are the dynamic movements of the skeleton?

• Types of Dynamic Motion
• Linear motion (gliding)
• Angular motion
• Rotation

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Linear Motion

• Pencil maintains vertical orientation, but
  changes position

Figure 92a, b
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Angular Motion

• Pencil maintains position, but changes orientation

Figure 92c
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Circumduction Rotation

• Pencil maintains position and orientation, but
  spins

• Circular angular motion

Figure 92e
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Planes (Axes) of Dynamic Motion

• Monaxial (1 axis)
• Biaxial (2 axes)
• Triaxial (3 axes)

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Types of Movements at Synovial Joints

• Terms describe
• plane or direction of motion
• relationship between structures

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Linear Motion

• Also called gliding
• 2 surfaces slide past each other
• between carpal or tarsal bones

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Flexion
Angular motion Anteriorposterior plane Reduces
angle between elements
Figure 93a
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Extension

• Angular motion
• Anteriorposterior plane
• Increases angle between elements
• Hyperextension
• Angular motion
• Extension past anatomical position

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Abduction
Figure 93b, c
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Abduction

• Angular motion
• Frontal plane
• Moves away from longitudinal axis
• Adduction
• Angular motion
• Frontal plane
• Moves toward longitudinal axis

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Circumduction

• Circular motion without rotation
• Angular motion

Figure 93d
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Rotation
Figure 94
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Rotation

• Direction of rotation from anatomical position
• Relative to longitudinal axis of body
• Left or right rotation
• Medial rotation (inward rotation)
• rotates toward axis
• Lateral rotation (outward rotation) rotates away
  from axis

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Pronation and Supination

• Pronation
• rotates forearm, radius over ulna
• Supination
• forearm in anatomical position

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Inversion and Eversion
Inversion twists sole of foot medially Eversion
twists sole of foot laterally
Figure 95a
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Dorsiflexion and Plantar Flexion

• Dorsiflexion
• flexion at ankle (lifting toes)
• Plantar flexion
• extension at ankle (pointing toes)

Figure 95b
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Opposition

• Thumb movement toward fingers or palm (grasping)

Figure 95c
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Protraction and Retraction
Figure 95d
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Protraction and Retraction

• Protraction
• moves anteriorly
• in the horizontal plane (pushing forward)
• Retraction
• opposite of protraction
• moving anteriorly (pulling back)

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Elevation and Depression

• Elevation
• moves in superior direction (up)
• Depression
• moves in inferior direction (down)

Figure 95e
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Lateral Flexion

• Bends vertebral column from side to side

Figure 95f
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What are the types of synovial joints, and the
relationship of motion to structure?
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Classification of Synovial Joints by Shape

• Gliding
• Hinge
• Pivot
• Ellipsoidal
• Saddle
• Ball-and-socket

A Functional Classification of Synovial Joints
PLAY
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Gliding Joints

• Flattened or slightly curved faces
• Limited motion (nonaxial)

Figure 96 (1 of 6)
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Hinge Joints

• Angular motion in a single plane (monaxial)

Figure 96 (2 of 6)
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Pivot Joints

• Rotation only (monaxial)

Figure 96 (3 of 6)
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Ellipsoidal Joints

• Oval articular face within a depression
• Motion in 2 planes (biaxial)

Figure 96 (4 of 6)
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Saddle Joints

• 2 concave faces, straddled (biaxial)

Figure 96 (5 of 6)
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Ball-and-Socket Joints

• Round articular face in a depression (triaxial)

Figure 96 (6 of 6)
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KEY CONCEPT

• A joint cant 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

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How do vertebrae in the vertebral column
articulate? Intervertebral Articulations
Figure 97
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Intervertebral Articulations

• C2 to L5 spinal vertebrae articulate
• at inferior and superior articular processes
  (gliding joints)
• between adjacent vertebral bodies (symphyseal
  joints)

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Intervertebral Discs

• Intervertebral discs
• pads of fibrocartilage
• separate vertebral bodies

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Disc Structure

• Anulus fibrosus
• tough outer layer
• attaches disc to vertebrae
• Nucleus pulposus
• elastic, gelatinous core
• absorbs shocks

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Vertebral Joints

• Also called symphyseal joints
• As vertebral column moves
• nucleus pulposus shifts
• disc shape conforms to motion

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Intervertebral Ligaments

• Bind vertebrae together
• Stabilize the vertebral column

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6 Intervertebral Ligaments

• Anterior longitudinal ligament
• connects anterior bodies
• Posterior longitudinal ligament
• connects posterior bodies
• Ligamentum flavum
• connects laminae

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6 Intervertebral Ligaments

• Interspinous ligament
• connects spinous processes
• Supraspinous ligament
• connects tips of spinous processes (C7 to sacrum)
• Ligamentum nuchae
• continues supraspinous ligament (C7 to skull)

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Damage to Intervertebral Discs
Figure 98
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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

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Movements of the Vertebral Column

• Flexion
• bends anteriorly
• Extension
• bends posteriorly
• Lateral flexion
• bends laterally
• Rotation

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Articulations and Movements of the Axial Skeleton
Table 93 (1 of 2)
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Articulations and Movements of the Axial Skeleton
Table 93 (2 of 2)
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What are the structures and functions of the
shoulder, elbow, hip, and knee joints, and what
is the relationship between joint strength and
mobility?
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The Shoulder Joint
Figure 99a
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The Shoulder Joint
Figure 99b
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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

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Structure of the Shoulder Joint

• Ball-and-socket diarthrosis
• Between head of humerus and glenoid cavity of
  scapula

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Socket of the Shoulder Joint

• Glenoid labrum
• deepens socket of glenoid cavity
• fibrocartilage lining
• extends past the bone

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Processes of the Shoulder Joint

• Acromion (clavicle) and coracoid process
  (scapula)
• project laterally, superior to the humerus
• help stabilize the joint

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Shoulder Ligaments

• Glenohumeral
• Coracohumeral
• Coracoacromial
• Coracoclavicular
• Acromioclavicular

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Shoulder Separation

• Dislocation of the shoulder joint

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Shoulder Muscles

• Also called rotator cuff
• supraspinatus
• infraspinatus
• subscapularis
• teres minor

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Shoulder Bursae

• Subacromial
• Subcoracoid
• Subdeltoid
• Subscapular

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The Elbow Joint
Figure 910
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The Elbow Joint

• A stable hinge joint
• With articulations between humerus, radius, and
  ulna

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Articulations of the Elbow

• Humeroulnar joint
• largest articulation
• trochlea of humerus and trochlear notch of ulna
• limited movement
• Humeroradial joint
• smaller articulation
• capitulum of humerus and head of radius

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Elbow Muscle

• Biceps brachii muscle
• attached to radial tuberosity
• controls elbow motion
• Elbow Ligaments
• Radial collateral
• Annular
• Ulnar collateral

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The Hip Joint
Figure 911a
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The Hip Joint
Figure 911b, c
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The Hip Joint

• Also called coxal joint
• Strong ball-and-socket diarthrosis
• Wide range of motion

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Structures of the Hip Joint

• Head of femur fits into it
• Socket of acetabulum
• Which is extended by fibrocartilage acetabular
  labrum

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Ligaments of the Hip Joint

• Iliofemoral
• Pubofemoral
• Ischiofemoral
• Transverse acetabular
• Ligamentum teres

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The Knee Joint
Figure 912a, b
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The Knee Joint

• A complicated hinge joint
• Transfers weight from femur to tibia

Figure 912c, d
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Articulations of the Knee Joint

• 2 femurtibia articulations
• at medial and lateral condyles
• 1 between patella and patellar surface of femur

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Menisci of the Knee

• Medial and lateral menisci
• fibrocartilage pads
• at femurtibia articulations
• cushion and stabilize joint
• give lateral support

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Locking Knees

• Standing with legs straight
• locks knees by jamming lateral meniscus between
  tibia and femur

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7 Ligaments of the Knee Joint

• Patellar ligament (anterior)
• 2 popliteal ligaments (posterior)
• Anterior and posterior cruciate ligaments (inside
  joint capsule)
• Tibial collateral ligament (medial)
• Fibular collateral ligament (lateral)

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Articulations of the Appendicular Skeleton
Table 94 (1 of 2)
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Articulations of the Appendicular Skeleton
Table 94 (2 of 2)
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What are the effects of aging on articulations,
and the most common clinical problems?
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Rheumatism

• A pain and stiffness of skeletal and muscular
  systems
• Arthritis
• All forms of rheumatism that damage articular
  cartilages of synovial joints

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Osteoarthritis

• Caused by wear and tear of joint surfaces, or
  genetic factors affecting collagen formation
• Generally in people over age 60

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Rheumatoid Arthritis

• An inflammatory condition
• Caused by infection, allergy, or autoimmune
  disease
• Involves the immune system

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Gouty Arthritis

• Occurs when crystals (uric acid or calcium
  salts)
• form within synovial fluid
• due to metabolic disorders

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Joint Immobilization

• Reduces flow of synovial fluid
• Can cause arthritis symptoms
• Treated by continuous passive motion (therapy)

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Bones and Aging

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

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Integration with Other Systems
Figure 913
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Bone Recycling

• Living bones maintain equilibrium between
• bone building (osteoblasts)
• and break down (osteoclasts)

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Factors Affecting Bone Strength

• Age
• Physical stress
• Hormone levels
• Calcium and phosphorus uptake and excretion
• Genetic and environmental factors

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Bones Support Body Systems

• The skeletal system
• supports and protects other systems
• stores fat, calcium, and phosphorus
• manufactures cells for immune system

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Body Systems Support Bones

• Disorders in other body systems can cause
• bone tumors
• osteoporosis
• arthritis
• rickets (demineralization)

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SUMMARY (1 of 5)

• Joint classification by motion and structure
• 4 types of synarthroses
• suture, gomphosis, synchondrosis, synostosis
• 2 types of amphiarthroses
• syndesmosis, symphysis

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SUMMARY (2 of 5)

• Structures of diarthroses
• 3 forms of dynamic motion
• linear or gliding, angular, rotation
• 3 planes of motion
• monaxial, biaxial, triaxial

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SUMMARY (3 of 5)

• Movements of synovial joints
• gliding, flexion, extension, abduction, rotation,
  pronation, inversion, dorsiflexion, opposition,
  protraction, depression, etc.

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SUMMARY (4 of 5)

• 6 structural types of synovial joints
• gliding
• hinge
• pivot
• ellipsoidal
• saddle
• ball-and-socket

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SUMMARY (5 of 5)

• Structures and movements of
• intervertebral articulations
• shoulder joint
• elbow joint
• hip joint
• knee joint
• Effects of aging on joints
• Relationship of the skeleton to other body
  systems