Chapter 9:
Articulations
A&P Biology 141
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
What are the major
categories of joints, and
the structure and
function of each
category?
Functional
Classification
Table 9–1
Functional
Classifications
• Synarthrosis:
• no movement
• Amphiarthrosis:
• little movement
• Diarthrosis:
• more movement
Synarthroses
• Also called immovable joints
• Fibrous or cartilaginous
connections
• May fuse over time
Amphiarthroses
• Also called slightly moveable
joints
• Fibrous or cartilaginous
connections
Diarthroses
• Synovial joints
• Also called freely moveable
joints
• Subdivided by type of motion
Structural Classification
Table 9–2
Structural
Classifications
•
•
•
•
Bony
Fibrous
Cartilaginous
Synovial
Synarthroses
(Immovable Joints)
• Are very strong
• Edges of bones may touch or
interlock
4 Types of Synarthrotic Joints
•
•
•
•
Suture
Gomphosis
Synchondrosis
Synostosis
Suture
• Bones interlocked
• Are bound by dense fibrous
connective tissue
• Are found only in skull
Gomphosis
• Fibrous connection (periodontal
ligament)
• Binds teeth to sockets
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
Amphiarthroses
• More moveable than synarthrosis
• Stronger than freely movable
joint
2 Types of Amphiarthroses
• Syndesmosis:
• bones connected by ligaments
• Symphysis:
• bones separated by fibrocartilage
What is the basic
structure
of a synovial joint, and
what are the common
accessory structures
and their functions?
Synovial Joints
(Diarthroses)
•
•
•
•
Also called moveable joints
At ends of long bones
Within articular capsules
Lined with synovial membrane
Articular Cartilages
• Pad articulating surfaces within
articular capsules:
• prevent bones from touching
• Smooth surfaces lubricated by
synovial fluid:
• reduce friction
Synovial Fluid
• Contains slippery
proteoglycans secreted by
fibroblasts
Functions of Synovial Fluid
1. Lubrication
2. Nutrient distribution
3. Shock absorption
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
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
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
Injuries
• Dislocation (luxation):
• articulating surfaces forced out of
position
• damages articular cartilage,
ligaments, joint capsule
• Subluxation:
• a partial dislocation
What are the dynamic
movements of the
skeleton?
Types of Dynamic Motion
• Linear motion (gliding)
• Angular motion
• Rotation
Linear Motion
• Pencil maintains
vertical
orientation, but
changes position
Figure 9–2a, b
Angular Motion
• Pencil maintains
position, but
changes
orientation
Figure 9–2c
Circumduction & Rotation
• Circular
angular motion
• Pencil maintains
position and
orientation, but spins
Figure 9–2e
Planes (Axes) of
Dynamic Motion
• Monaxial (1 axis)
• Biaxial (2 axes)
• Triaxial (3 axes)
Types of Movements
at Synovial Joints
• Terms describe:
• plane or direction of motion
• relationship between structures
Linear Motion
• Also called gliding
• 2 surfaces slide past each
other:
• between carpal or tarsal bones
Flexion
Angular motion
Anterior–posterior
plane
Reduces angle between
elements
Figure 9–3a
Extension
• Angular motion
• Anterior–posterior plane
• Increases angle between
elements
Hyperextension
• Angular motion
• Extension past anatomical
position
Abduction
Figure 9–3b, c
Abduction
• Angular motion
• Frontal plane
• Moves away from longitudinal
axis
Adduction
• Angular motion
• Frontal plane
• Moves toward longitudinal
axis
Circumduction
• Circular
motion
without
rotation
• Angular
motion
Figure 9–3d
Rotation
Figure 9–4
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
Pronation and
Supination
• Pronation:
• rotates forearm, radius over ulna
• Supination:
• forearm in anatomical position
Inversion and Eversion
Inversion:
twists sole of foot
medially
Eversion:
twists sole of foot
laterally
Figure 9–5a
Dorsiflexion and Plantar
Flexion
• Dorsiflexion:
flexion at ankle (lifting
toes)
• Plantar flexion:
extension at ankle
(pointing toes)
Figure 9–5b
Opposition
• Thumb movement
toward fingers or
palm (grasping)
Figure 9–5c
Protraction and
Retraction
Figure 9–5d
Protraction and
Retraction
• Protraction:
• moves anteriorly
• in the horizontal plane (pushing
forward)
• Retraction:
• opposite of protraction
• moving anteriorly (pulling back)
Elevation and
Depression
• Elevation:
moves in superior
direction (up)
• Depression:
moves in inferior
direction (down)
Figure 9–5e
Lateral Flexion
• Bends
vertebral
column from
side to side
Figure 9–5f
What are the types of
synovial joints, and the
relationship
of motion to structure?
Classification of
Synovial Joints by
Shape
•
•
•
•
•
•
Gliding
Hinge
Pivot
Ellipsoidal
Saddle
Ball-and-socket
PLAY
A Functional Classification of Synovial Joints
Gliding Joints
• Flattened or slightly curved
faces
• Limited motion (nonaxial)
Figure 9–6 (1 of 6)
Hinge Joints
• Angular motion in a single plane
(monaxial)
Figure 9–6 (2 of 6)
Pivot Joints
• Rotation only (monaxial)
Figure 9–6 (3 of 6)
Ellipsoidal Joints
• Oval articular face within a
depression
• Motion in 2 planes (biaxial)
Figure 9–6 (4 of 6)
Saddle Joints
• 2 concave faces, straddled
(biaxial)
Figure 9–6 (5 of 6)
Ball-and-Socket Joints
• Round articular face in a
depression (triaxial)
Figure 9–6 (6 of 6)
KEY CONCEPT
• A joint can’t 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
How do vertebrae in the
vertebral column
articulate?
Intervertebral
Articulations
Figure 9–7
Intervertebral
Articulations
• C2 to L5 spinal vertebrae
articulate:
• at inferior and superior articular
processes (gliding joints)
• between adjacent vertebral bodies
(symphyseal joints)
Intervertebral Discs
• Intervertebral discs:
• pads of fibrocartilage
• separate vertebral bodies
Disc Structure
• Anulus fibrosus:
• tough outer layer
• attaches disc to vertebrae
• Nucleus pulposus:
• elastic, gelatinous core
• absorbs shocks
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
6 Intervertebral
Ligaments
• Anterior longitudinal ligament:
• connects anterior bodies
• Posterior longitudinal ligament:
• connects posterior bodies
• Ligamentum flavum:
• connects laminae
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)
Damage to
Intervertebral Discs
Figure 9–8
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
Movements of the
Vertebral Column
• Flexion:
• bends anteriorly
• Extension:
• bends posteriorly
• Lateral flexion:
• bends laterally
• Rotation
Articulations and
Movements
of the Axial Skeleton
Table 9–3 (1 of 2)
Articulations and
Movements
of the Axial Skeleton
Table 9–3 (2 of 2)
What are the structures
and functions of the
shoulder, elbow, hip, and
knee
joints, and what is the
relationship between
joint strength and
mobility?
The Shoulder Joint
Figure 9–9a
The Shoulder Joint
Figure 9–9b
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
Structure of the
Shoulder Joint
• Ball-and-socket diarthrosis
• Between head of humerus and
glenoid cavity of scapula
Socket of the Shoulder
Joint
• Glenoid labrum:
• deepens socket of glenoid cavity
• fibrocartilage 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
Shoulder Ligaments
•
•
•
•
•
Glenohumeral
Coracohumeral
Coracoacromial
Coracoclavicular
Acromioclavicular
Shoulder Separation
• Dislocation of the shoulder joint
Shoulder Muscles
• Also called rotator cuff:
•
•
•
•
supraspinatus
infraspinatus
subscapularis
teres minor
Shoulder Bursae
•
•
•
•
Subacromial
Subcoracoid
Subdeltoid
Subscapular
The Elbow Joint
Figure 9–10
The Elbow Joint
• A stable hinge joint
• With articulations between
humerus, radius, and ulna
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
Elbow Muscle
• Biceps brachii muscle:
• attached to radial tuberosity
• controls elbow motion
Elbow Ligaments
• Radial collateral
• Annular
• Ulnar collateral
The Hip Joint
Figure 9–11a
The Hip Joint
Figure 9–11b, c
The Hip Joint
• Also called coxal joint
• Strong ball-and-socket
diarthrosis
• Wide range of motion
Structures of the Hip
Joint
• Head of femur fits into it
• Socket of acetabulum
• Which is extended by
fibrocartilage acetabular
labrum
Ligaments of the Hip
Joint
•
•
•
•
•
Iliofemoral
Pubofemoral
Ischiofemoral
Transverse acetabular
Ligamentum teres
The Knee Joint
Figure 9–12a, b
The Knee Joint
• A complicated hinge joint
• Transfers weight from femur to tibia
Figure 9–12c, d
Articulations of the
Knee Joint
• 2 femur–tibia articulations:
• at medial and lateral condyles
• 1 between patella and patellar
surface of femur
Menisci of the Knee
• Medial and lateral menisci:
•
•
•
•
fibrocartilage 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
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)
Articulations of the
Appendicular Skeleton
Table 9–4 (1 of 2)
Articulations of the
Appendicular Skeleton
Table 9–4 (2 of 2)
What are the effects of
aging on articulations,
and the most common
clinical problems?
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
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
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
Figure 9–13
Bone Recycling
• Living bones maintain
equilibrium between:
• bone building (osteoblasts)
• and break down (osteoclasts)
Factors Affecting Bone
Strength
1.
2.
3.
4.
Age
Physical stress
Hormone levels
Calcium and phosphorus
uptake and excretion
5. Genetic and environmental
factors
Bones Support Body
Systems
• The skeletal system:
• supports and protects other
systems
• stores fat, calcium, and
phosphorus
• manufactures cells for immune
system
Body Systems Support
Bones
• Disorders in other body systems
can cause:
•
•
•
•
bone tumors
osteoporosis
arthritis
rickets (demineralization)
SUMMARY (1 of 5)
• Joint classification by motion
and structure
• 4 types of synarthroses:
• suture, gomphosis, synchondrosis,
synostosis
• 2 types of amphiarthroses:
• syndesmosis, symphysis
SUMMARY (2 of 5)
• Structures of diarthroses
• 3 forms of dynamic motion:
• linear or gliding, angular, rotation
• 3 planes of motion:
• monaxial, biaxial, triaxial
SUMMARY (3 of 5)
• Movements of synovial joints:
• gliding, flexion, extension,
abduction, rotation, pronation,
inversion, dorsiflexion, opposition,
protraction, depression, etc.
SUMMARY (4 of 5)
• 6 structural types of synovial
joints:
•
•
•
•
•
•
gliding
hinge
pivot
ellipsoidal
saddle
ball-and-socket
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