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Joints
Part A
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
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8
Joints (Articulations)

Although joints are the weakest parts of the
skeleton they allows our body to do a great variety
of motions

Articulation – site where two or more bones meet

Functions of joints

1.- Give the skeleton mobility

2.- Hold the skeleton together
Joints are classified by the structure and by their
functions
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Classification of Joints: Structural
 Structural classification focuses on the material
binding bones together and whether or not a joint
cavity is present
 The three structural classifications are:
 Fibrous (immovible)
 Cartilaginous
 Synovial (freely movable)
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Joints Classes
Structural
class
Characteristics
Fibrous
Bone ends/parts
united by collagenic
fibers
Types
Mobility
-Suture
Immobile
-Syndesmosis
Slightly mobile
-Gomphorosis
Immobile
Cartilaginous Bone ends/parts
united by collagenic
fibers
-Synchondrosis
Immobile
-Symphysis
Slightly mobile
Synovial
-Plane -Hinge
Freely movable
(diartrosis)
Bone ends/parts
covered with
articular cartilage and
enclosed within and
articul. capsule lined
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with synovial memb.
-Pivot -Saddle
-Condyloid
-Ball and socket
Classification of Joints: Functional
 Functional classification is based on the amount of
movement allowed by the joint
 The three functional classes of joints are:
 Synarthroses – immovable ( syn= together)
 Amphiarthroses – slightly movable (amphi= on
both sides)
 Diarthroses – freely movable (through, apart).
Predominates in limbs
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Fibrous Structural Joints
 The bones are joined by fibrous tissues
 There is no joint cavity
 Most are immovable. The amount of movement
allowed depends on the length of the connective
tissue fibers uniting the bones
 There are three types – sutures, syndesmoses, and
gomphoses
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Fibrous Structural Joints: Sutures
 Occur only between the bones of the skull
 Comprised of interlocking junctions completely
filled with connective tissue fibers
 Bind bones tightly together, but allow for growth
during youth
 In middle age, skull bones fuse and are called
synostoses
 Because movement of the cranial bones would
damage the brain, the immovable nature of sutures
is a protective adaptation
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Fibrous Structural Joints: Sutures
Figure 8.1a
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Fibrous Structural Joints: Syndesmoses
 Bones are connected by a fibrous tissue ligament
 Movement varies from immovable to slightly
variable
 Examples include the connection between the tibia
and fibula, and the radius and ulna
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Fibrous Structural Joints: Syndesmoses
Figure 8.1b
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Fibrous Structural Joints: Gomphoses
 The term gomphosis comes from the Greek gompho
meaning “nail” or bolt”
 Is a peg-in-socket fibrous joint. The only example is
the articulation of a tooth and its alveolar socket
 The fibrous connection is the periodontal ligament
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Cartilaginous Joints
 Articulating bones are united by cartilage
 Lack a joint cavity
 Two types – synchondroses and symphyses
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Cartilaginous Joints: Synchondroses
 A bar or plate of hyaline cartilage unites the bones
 All synchondroses are synarthrotic
 Examples include:
 Epiphyseal plates of children
 Joint between the costal cartilage of the first rib and
the sternum
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Cartilaginous Joints: Synchondroses
Figure 8.2a, b
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Cartilaginous Joints: Symphyses (Table 8.2, pp259
 Symphases: “growing together”
 Hyaline cartilage covers the articulating surface of
the bone and is fused to an intervening pad of
fibrocartilage
 Amphiarthrotic joints designed for strength and
flexibility
 Examples include intervertebral joints and the pubic
symphysis of the pelvis
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Cartilaginous Joints: Symphyses
Figure 8.2c
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Synovial Joints
 Those joints in which the articulating bones are
separated by a fluid-containing joint cavity
 All are freely movable diarthroses
 Examples – all limb joints, and most joints of the
body
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Synovial Joints: General Structure
 Synovial joints all have the following
 1.- Articular cartilage
 2.- Joint (synovial) cavity
 3.- Articular capsule
 4.- Synovial fluid
 5.- Reinforcing ligaments
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Synovial Joints: General Structure
Figure 8.3a, b
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Synovial Joints: Friction-Reducing Structures
 Bursae and tendon sheaths are not strictly part of
synovial joints, but they are closely associated with
them
 Bursae – flattened, fibrous sacs lined with synovial
membranes and containing synovial fluid
 Common where ligaments, muscles, skin, tendons,
or bones rub together
 Tendon sheath – elongated bursa that wraps
completely around a tendon
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Synovial Joints: Friction-Reducing Structures
Figure 8.4
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Synovial Joints: Stability
 Stability is determined by:
 Articular surfaces – shape determines what
movements are possible
 Ligaments – unite bones and prevent excessive or
undesirable motion
 Muscle tone is accomplished by:
 Muscle tendons across joints acting as stabilizing
factors
 Tendons that are kept tight at all times by muscle
tone
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Synovial Joints: Movement
 Every skeletal muscle of the body is attached to
bone or other connective tissue structures at no
fewer than two points.
 The two muscle attachments across a joint are:
 Origin – attachment to the immovable bone
 Insertion – attachment to the movable bone
 Described as movement along transverse, frontal, or
sagittal planes
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Synovial Joints: Range of Motion
 Range of motion allowed by synovial joints varies
from:
 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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Range Motion
 Range of motion varies greatly in different people.
There are three types of movements:
 Gliding
 Angular
 Rotation
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Gliding Movements ( Also known as translation)
 Are the simplest joint movements
 One flat bone surface glides or slips over another
similar surface
 Examples – intercarpal and intertarsal joints, and
between the flat articular processes of the vertebrae
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Angular Movement ( Increase or decrease the angle between two
bones)
 Flexion — bending movement that decreases the angle of
the joint. Ex Bending the head forward on the chest
 Extension — reverse of flexion; joint angle is increased. Ex
Bending the head backward beyond its straight position
 Dorsiflexion and plantar flexion — up and down movement
of the foot
 Abduction — movement away from the midline
 Adduction — movement toward the midline
 Circumduction — movement describes a cone in space
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Gliding Movement
Figure 8.5a
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Angular Movement
Figure 8.5b
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Angular Movement
Figure 8.5c, d
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Angular Movement
Figure 8.5e, f
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Rotation
 The turning of a bone
around its own long
axis
 Examples
 Between first two
vertebrae
 Hip and shoulder
joints
Figure 8.5g
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Special Movements
 Certain movements do not fit into any of the above
categories and occur at only a few joints. There are:
 Supination and pronation (forearm)
 Inversion and eversion (foot)
 Protraction and retraction (mandible)
 Elevation and depression (mandible, chewing)
 Opposition (thumb)
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Special Movements
Figure 8.6a
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Special Movements
Figure 8.6b
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Special Movements
Figure 8.6c
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Special Movements
Figure 8.6d
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Special Movements
Figure 8.6e
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