Transcript Articulations

Articulations
Fibrous Joints
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Include all articulations where bones are held tightly together by
fibrous connective tissue—called sutural ligament
Very little material separates the ends of bones, no appreciable
movement is allowed
Also called synarthroses (syn=together, arthron=joint)—
nonmovable joint
Two Types:
 Sutures
 Syndesmoses
Sutures
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Bone interdigitations (grooves) fit closely and firmly together
Connecting fibers spanning between bones very short
Found only in flat bones of skull
 In early adulthood, fibers of suture are replaced by bone
 Bones fuse together
 Called synostosis (held together by bone)
Syndesmoses
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Syndesmosis=together by bands
Held together by fibrous connective tissue
Bone ends farther apart than in suture, thus connective tissue
fibers joining bones longer
Bones not held as firmly as suture, thus a “give” motion occurs
Examples:
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Joint between distal ends of tibia and fibula
Joints in the mid-radius/ulna and the mid-tibia/fibula
Cartilaginous Joints
Bones united by cartilage
 Sight movement is possible—called
amphiarthroses (amphi=on both sides)
 Two types
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– Synchondroses
– symphyses
Synchondroses
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“together by cartilage”
Held together by hyaline cartilage
Many temporary, eventually replaced by bone
Examples
– Area between the epiphyses and the diaphysis of long bones
– Certain skull bones
– Joint of first ten ribs and the costal cartilage is a permanent
synchondroses
Symphyses
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Aricular surfaces covered with thin layer of hyaline
cartilage
A fibrocartilaginous pad separates the bones—the pads
(discs) are compressible, serve as shock absorbers
Examples:
– Intervertebral discs: pads between adjacent vertebrae
– The junction of the pubis bones—pubic synapse
– The midline symphysis between the two halves of the mandible
Synovial Joints
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The majority of joints
Freely movable—limited by ligaments, muscles, tendons, or adjoining
bones
Referred to as diarthroses=“through joint” indicating only slight limitations
to the movement of such joints
Have a fluid-filled joint cavity
Four distinguishing features:
 Articular cartilage (thin layer of hyaline cartilage covering surface of
bone
 Articular capsule (a double-layer membrane surrounding joint)
 Synovial membrane (loose connective tissue whose inner surface
supplied by capillaries
 Synovial fluid (thick fluid that provides nutrients to articular cartilages,
lubricates joint)
Synovial Joints continued
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Synovial joint also may have articular discs or menisci
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Articular discs divide synovial cavity into two separate cavities
Examples:
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Jaw
Sternoclavicular joint
Distal radioulnar joint
Synovial membranes form two structures that are not actually part of the
synovial joint but are associated with them:
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Bursae: a small sac lined with synovial membranes. Act as cushions between
the structures they separate
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Some are subcutaneous—between bone and skin
Most located between tendons and bone
Tendon Sheaths: cylindrical synovial sacs that wrap around tendons, found
where tendons cross joints
Synovial Joint Movement
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Identified by the type of movement they permit
Many have axis of rotation
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Uniaxial joints—have only one axis of motion and move on one plane (elbow
and knee)
Biaxial joints—have two axes allowing movement in two planes that are at
right angles to each other (between tarsals and metatarsals, carpals and
metacarpals)
Triaxial joints—more than two axes and move in three planes (hip and
shoulder)
General movements: gliding, angular, circumduction, and rotation
Gliding
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Simplest most common type of movement
Surfaces of adjoining bones move back and forth
The articulating surfaces are flat or slightly concave
Examples:
 Joint between head of ribs and the bodies of the vertebrae
 Joint between the tubercles of the ribs and the transverse
processes of the vertebrae
 Intercarpal and intertarsal joints
Angular Movement
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Flexion
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When a bone is moved in an anterior-posterior plane in a manner as to decrease
the angle between in and the adjoining bones
Example: bending the elbow, bringing the thigh up toward the abdomen,
bringing the calf of the leg up toward the back of the thigh
Pulling the heel upward, lowering the toe region of the foot is plantar flexion
Extension
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Opposite of flexion
Causes the angle between adjoining bones to increase
Occurs when a flexed joint is placed back in its anatomical position
Hyperextension occurs when part is moved beyond a straight position—arching
the back or bringing the limbs posteriorly beyond the plane of the body
Raising the toe region toward the shin is called dorsiflexion
Angular movement continued
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Abduction
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Adduction
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When a part is moved away from the midline of the body
Example, moving the fingers away from the midline of the hand
The opposite of abduction
When a part is moved toward the midline of the body
Example: moving the fingers toward the midline of the hand
Circumduction
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Delineates a cone, the base of the bone is outlined by the movement of the
distal end of the bone, with the apex of the cone lying in the articular cavity
Movement combines flexion, abduction, extension, and adduction
Example: shoulder and hip
Angular movement continued
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Rotation
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Supination
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The motion of a bone around a central axis without any displacement of that
axis
If the anterior surface of a bone moves inward, called medial rotation
If the anterior surface turns outward it is lateral rotation
The outward rotation of the fore-arm, causing the palm to face upward or
forward and the radius and ulna to be parallel
Supination occurs when the arms in the anatomical position
Pronation
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The inward rotation of the fore-arm, causing the radius to cross diagonally over
the ulna and the palm to face downward or backward
Angular Movement continued
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Special movements
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Elevation: raising the part, examples: raising the scapula or mandible
Depression: lowering the part, example: lowering scapula or mandible
Inversion: twisting of the foot so that the sole faces inward with its inner
margin raised
Eversion: twisting of the foot so that the sole faces outward with its outer
margin raised
Protraction: the motion that moves a part forward, such as the mandible
Retraction: the motion that returns a protracted part to its usual position
Types of Synovial Joints
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Nonaxial joints
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Gliding (arthrodial) joints: formed primarily by the apposition of flat, or only
slightly curved, articular surfaces. Movement is allowed in any direction,
being llimited only by ligaments or bony processes that surround the
articulation. Example: vertebrae and between most carpal and tarsal bones
Uniaxial joints
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Hinge (ginglymus) joints: the articular surfaces are shaped such that the only
movements possible are flexion and extension. Examples: elbow, knee, and
joints between the phalanges
Pivot (trochoid) joints: rotation around the longitudinal axis of the bone.
Examples: rotation of atlas around the axis, proximal articulations between the
radius and ulna
Types of Synovial joints continued
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Biaxial Joints
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Condyloid (ellipsoid) joints: have one articular surface slightly concave and
other slightly convex, movement is allowed in two planes that are at right
angles to each other. Flexion, extension, abduction, and adduction can occur
at condyloid joints. Circumduction is possible, but axial rotation is not.
Examples: between radius and carpals, the occipital condyles of skill and the
atlas, metacarpophalangeal and metatrasophalangeal joints
Saddle joints: allow the same movement as the condyloid joints. The articular
surface of each bone is concave in one direction and convex in the other; the
bones fit together just as two saddles would if the riding surface of one were
rotated 90 degrees. Only one saddle joint, the thumb
Triaxial Joints
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Spheroid (ball and socket) joints: formed by a spherical head of one bone
fitting into a cup-shaped cavity on another. Movement in indefinite number of
axes—flexion, extension, abduction, adduction, circumduction, medial and
lateral rotation. Only 2—shoulder and hip
Clinical Significance of Articulations
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Sprains
 Result from the twisting or overstretching of a joint causing a ligament to
tear or separate from bony attachment---excessive tissue fluid accumulates
and causes swelling
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Dislocations
 Articular surfaces are forcibly displaced
 Severe dislocations result in bones and surrounding tendons and ligaments
being damaged
 Most common in shoulder, thumb, and fingers
Clinical Continued
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Bursitis
 When one or more bursae surrounding a joint becomes inflamed
 May result from injury, heavy exercise, or infection
 Results in discomfort and limiting motion
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Tendinitis
 The inflammation of tendon sheaths around a joint
 Local tenderness at the point of inflammation and severe pain upon
movement of joint
 Results from trauma to, or excessive use of a joint
 Most common in wrist, elbow, or shoulder
Clinical continued
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Slipped Disc
 The relatively soft nucleus pulposa within the intervertebral disc is
squeezed to the side of the disc
 Results from trauma or improper distribution of weight along the vertebral
column resulting in poor posture
 Causes the disc to protrude and/or rupture—result in severe pain along the
path of nerves, numbness, if nerve damage results—weakness and
degeneration of muscles
Clinical continued
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Torn Menisci
 Sudden changes of direction while bearing body weight can cause the
menisci of knee to tear loose
 Causes severe pain and swelling of the joint
 Arthroscopic surgery repairs damaged menisci
Arthroscope (needlelike viewing instrument ) inserted in the knee
► Fiber-optic light allows doc to see injury and small incisions are made to insert
cutting instruments
► Performed under local anesthesia, patient returns home same day
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Clinical Continued
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Arthritis
 Pathological changes in the joint membranes, cartilage, and bone cause
swelling and pain
 Causes of arthritis unknown, but trauma, infection by bacteria
(staphylococci, streptococci, and gonococci) and metabolic disorders have
been implicated
 May be genetically inherited
 Types:
Osteoarthritis
► Rheumatoid arthritis
► Gouty arthritis
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Osteoarthritis
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Most common form of arthritis
Chronic inflammation that causes the articular cartilage in the affected
joint to degenerate
Causes pain, swelling, and stiffness
As articular cartilage degenerates, bony spurs develop and restrict the
movement of the joint
Rheumatoid Arthritis
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Severely damages the joint
Affects principally small joints of the body—hands, feet, knees, ankles,
elbows, and wrists
Affects women more than men
Begins with inflammation of the synovial membrane of the joint,
swelling and pain occur--Inflamed synovial fluid produces pannus
(abnormal tissue that grows over surface of articular cartilage)
Articular cartilage beneath pannus is destroyed, pannus fills joint space
and becomes invaded by fibrous tissue—restricts movement
Calcification of pannus may ankylose (fuse) the joint
Gouty Arthritis
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Gout is characterized by sudden severe pain and swelling of joint
Primarily affects toes, insteps, ankles, heels, knees, and wrists
More common in males
Inherited genetic defect that causes either and increased production of
uric acid or a reduction in the ability of the kidney to excrete uric acid
Causes hypouricemia (increase level of uric acid in blood)
Body fluids become supersaturated and result in the formation of
sodium urate crystals in the soft tissues of the body as well as joints
Causes inflammation that eventually may erode the articular cartilage
and underlying bone—causes intense pain and immobility
Effects of Aging
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Aging causes a progressive loss of cartilage surface of joints
Called degenerative osteoarthropathy
Varies greatly from individual to individual
Women develop bony swellings (Heberden’s nodes) in terminal
phalanges
Men most commonly develop degenerative osteoarthropathy n spine
By age 80, virtually everyone has some degenerative osteoarthropathy
of knee and elbow, and to some degree hip and shoulder
Chronic pain and pressure result