1. 8
Joints: Part A

2. Joints (Articulations)
Site where two or more bones meet
Functions of joints
Give skeleton mobility
Hold skeleton together
Two classifications
Functional
Structural
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3. Functional Classification of Joints
Based on
Amount of movement joint allows
Three functional classifications:
Synarthroses—immovable joints
Amphiarthroses—slightly movable joints
Diarthroses—freely movable joints
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4. Structural Classification of Joints
Based on
Material binding bones together
Presence/absence of joint cavity
Three structural classifications:
Fibrous joints
Cartilaginous joints
Synovial joints
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5. Bones joined by dense fibrous connective tissue No joint cavity
Fibrous Joints
Bones joined by dense fibrous connective tissue
No joint cavity
Most synarthrotic (immovable)
Depends on length of connective tissue fibers
Three types:
Sutures
Syndesmoses
Gomphoses
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6. Fibrous Joints: Sutures
Rigid, interlocking joints
Immovable joints for protection of brain
Contain short connective tissue fibers
Allow for growth during youth
In middle age, sutures ossify and fuse
Called Synostoses
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7. Suture Suture line Joint held together with very short,
Figure 8.1a Fibrous joints.
Suture
Joint held together with very short,
interconnecting fibers, and bone edges
interlock. Found only in the skull.
Suture
line
Dense
fibrous
connective
tissue
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8. Fibrous Joints: Syndesmoses
Bones connected by ligaments (bands of fibrous tissue)
Fiber length varies so movement varies, i.e.,
Little to no movement at distal tibiofibular joint
Large amount of movement at interosseous membrane connecting radius and ulna
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9. Joint held together by a ligament.
Figure 8.1b Fibrous joints.
Syndesmosis
Joint held together by a ligament.
Fibrous tissue can vary in length, but
is longer than in sutures.
Fibula
Tibia
Ligament
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10. Fibrous Joints: Gomphoses
Peg-in-socket joints of teeth in alveolar sockets
Fibrous connection is the periodontal ligament
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11. “Peg in socket” fibrous joint. Periodontal ligament holds
Figure 8.1c Fibrous joints.
Gomphosis
“Peg in socket” fibrous joint.
Periodontal ligament holds
tooth in socket.
Socket of
alveolar
process
Root of
tooth
Periodontal
ligament
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12. Bones united by cartilage No joint cavity Not highly movable
Cartilaginous Joints
Bones united by cartilage
No joint cavity
Not highly movable
Two types:
Synchondroses
Symphyses
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13. Cartilaginous Joints: Synchondroses
Bar/plate of hyaline cartilage unites bones e.g.,
Temporary epiphyseal plate joints
Become synostoses after plate closure
Cartilage of 1st rib with manubrium
~ All are synarthrotic
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14. Bones united by hyaline cartilage
Figure 8.2a Cartilaginous joints.
Synchondroses
Bones united by hyaline cartilage
Sternum
(manubrium)
Epiphyseal
plate (temporary
hyaline cartilage
joint)
Joint between first
rib and sternum
(immovable)
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15. Cartilaginous Joints: Symphyses
Fibrocartilage unites bone
Hyaline cartilage present as articular cartilage
Strong, flexible amphiarthroses
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16. Bones united by fibrocartilage
Figure 8.2b Cartilaginous joints.
Symphyses
Bones united by fibrocartilage
Body of vertebra
Fibrocartilaginous
intervertebral disc
(sandwiched between
hyaline cartilage)
Pubic symphysis
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17. Bones separated by fluid-filled joint cavity All are diarthrotic
Synovial Joints
Bones separated by fluid-filled joint cavity
All are diarthrotic
Include ~ all limb joints; most joints of body
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18. Synovial Joints: Six Distinguishing Features
1. Articular cartilage: hyaline cartilage
Prevents crushing of bone ends
2. Joint (synovial) cavity
Small, fluid-filled potential space
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19. Synovial Joints: Six Distinguishing Features
3. Articular (joint) capsule
Two layers
External Fibrous layer
Dense irregular connective tissue
Inner Synovial membrane
Loose connective tissue
Makes synovial fluid
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20. Synovial Joints: Six Distinguishing Features
4. Synovial fluid
Viscous, slippery filtrate of plasma and hyaluronic acid
Lubricates and nourishes articular cartilage
Contains phagocytic cells to remove microbes and debris
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21. Ligament Joint cavity (contains synovial fluid) Articular (hyaline)
Figure 8.3 General structure of a synovial joint.
Ligament
Joint cavity
(contains
synovial fluid)
Articular (hyaline)
cartilage
Fibrous
layer
Synovial
membrane
(secretes
synovial
fluid)
Articular
capsule
Periosteum
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22. Synovial Joints: Six Distinguishing Features
5. Different types of reinforcing ligaments
Capsular
Thickened part of fibrous layer
Extracapsular
Outside the capsule
Intracapsular
Deep to capsule; covered by synovial membrane
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23. Synovial Joints: Six Distinguishing Features
6. Nerves and blood vessels
Nerve fibers detect pain, monitor joint position and stretch
Capillary beds supply filtrate for synovial fluid
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24. Other Features of Some Synovial Joints
Fatty pads
For cushioning between fibrous layer and synovial membrane or bone
Articular discs (menisci)
Fibrocartilage separates articular surfaces to improve "fit" of bone ends, stabilize joint, and reduce wear and tear
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25. Structures Associated with Synovial Joints
Bursae
Sacs lined with synovial membrane
Contain synovial fluid
Reduce friction where ligaments, muscles, skin, tendons, or bones rub together
Tendon Sheaths
Elongated bursa wrapped completely around tendon subjected to friction
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26. Frontal section through the right shoulder joint
Figure 8.4a Bursae and tendon sheaths.
Acromion
of scapula
Subacromial
bursa
Joint cavity
containing
synovial fluid
Fibrous layer of
articular capsule
Articular
cartilage
Tendon
sheath
Synovial
membrane
Tendon of
long head
of biceps
brachii muscle
Fibrous
layer
Humerus
Frontal section through the right shoulder joint
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27. Enlargement of (a), showing how a bursa eliminates friction where
Figure 8.4b Bursae and tendon sheaths.
Bursa rolls
and lessens
friction.
Humerus head
rolls medially as
arm abducts.
Humerus moving
Enlargement of (a), showing how
a bursa eliminates friction where
a ligament (or other structure) would
rub against a bone
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28. Three Stabilizing Factors at Synovial Joints
Shapes of articular surfaces (minor role)
Ligament number and location (limited role)
Muscle tendons that cross joint (most important)
Muscle tone keeps tendons taut
Extremely important in reinforcing shoulder and knee joints and arches of the foot
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29. Summary of Characteristics of Body Joints
Consult Table 8.2 for:
Joint names
Articulating bones
Structural classification
Functional classification
Movements allowed
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30. Table 8.2 Structural and Functional Characteristics of Body Joints (1 of 4)
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31. Table 8.2 Structural and Functional Characteristics of Body Joints (2 of 4)
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32. Table 8.2 Structural and Functional Characteristics of Body Joints (3 of 4)
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33. Table 8.2 Structural and Functional Characteristics of Body Joints (4 of 4)
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34. Synovial Joints: Movements Allowed
All muscles attach to bone or connective tissue at no fewer than two points
Origin—attachment to immovable bone
Insertion—attachment to movable bone
Muscle contraction causes insertion to move toward origin
Movements occur along transverse, frontal, or sagittal planes
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35. Synovial Joints: Range of Motion
Nonaxial—slipping movements only
Uniaxial—movement in one plane
Biaxial—movement in two planes
Multiaxial—movement in or around all three planes
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36. Three General Types of Movements at Synovial Joints
1. Gliding
2. Angular movements
Flexion, extension, hyperextension
Abduction, adduction
Circumduction
3. Rotation
Medial and lateral rotation
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37. One flat bone surface glides or slips over another similar surface
Gliding Movements
One flat bone surface glides or slips over another similar surface
Examples:
Intercarpal joints
Intertarsal joints
Between articular processes of vertebrae
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38. Increase or decrease angle between two bones
Angular Movements
Increase or decrease angle between two bones
Movement along sagittal plane
Flexion—decreases the angle of the joint
Extension—increases the angle of the joint
Hyperextension—excessive extension beyond normal range of motion
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39. Movement along frontal plane
Angular Movements
Movement along frontal plane
Abduction—movement away from the midline
Adduction—movement toward the midline
Circumduction
Involves flexion, abduction, extension, and adduction of limb
Limb describes cone in space
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40. Turning of bone around its own long axis
Rotation
Turning of bone around its own long axis
Toward midline or away from it
Medial and lateral rotation
Examples:
Between C1 and C2 vertebrae
Rotation of humerus and femur
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41. Gliding movements at the wrist
Figure 8.5a Movements allowed by synovial joints.
Gliding
Gliding movements at the wrist
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42. Hyperextension Extension Flexion
Figure 8.5b Movements allowed by synovial joints.
Hyperextension
Extension
Flexion
Angular movements: flexion, extension,
and hyperextension of the neck
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43. Extension Hyperextension Flexion
Figure 8.5c Movements allowed by synovial joints.
Extension
Hyperextension
Flexion
Angular movements: flexion, extension, and
hyperextension of the vertebral column
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44. Figure 8.5d Movements allowed by synovial joints.
Flexion
Hyper-
extension
Extension
Flexion
Extension
Angular movements: flexion, extension, and hyperextension at the shoulder and knee
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45. Abduction Circumduction Adduction
Figure 8.5e Movements allowed by synovial joints.
Abduction
Circumduction
Adduction
Angular movements: abduction, adduction, and
circumduction of the upper limb at the shoulder
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46. Rotation of the head, neck, and lower limb
Figure 8.5f Movements allowed by synovial joints.
Rotation
Lateral
rotation
Medial
rotation
Rotation of the head, neck, and lower limb
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47. Special Movements at Synovial Joints
Supination and pronation of radius and ulna
Dorsiflexion and plantar flexion of foot
Inversion and eversion of foot
Protraction and retraction
Elevation and depression of mandible
Opposition of thumb of mandible
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48. Pronation (P) and supination (S)
Figure 8.6a Special body movements.
PLAY
A&P Flix™: Movement at the Knee Joint
PLAY
A&P Flix™: Muscles of the forearm
PLAY
A&P Flix™: Muscles of the forearm
Pronation
(radius rotates
over ulna)
Supination
(radius and ulna
are parallel) P S
Pronation (P) and supination (S)
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49. Dorsiflexion and plantar flexion
Figure 8.6b Special body movements.
Dorsiflexion
Plantar flexion
Dorsiflexion and plantar flexion
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50. Inversion and eversion
Figure 8.6c Special body movements.
Inversion
Eversion
Inversion and eversion
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51. Protraction and retraction
Figure 8.6d Special body movements.
Protraction
of mandible
Retraction
of mandiblet
Protraction and retraction
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52. Elevation and depression
Figure 8.6e Special body movements.
Elevation
of mandible
Depression
of mandible
Elevation and depression
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53. Opposition Opposition Figure 8.6f Special body movements.
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