Download CHAPTER 8

11/25/2015
CHAPTER 8

Joints or articulations are where two or more bones
meet




Classification of joints is based on amount of the
movement allowed by the joint
Three functional classifications:




1. They function to give our skeleton mobility
2. They hold the skeleton together and protect it
Synarthroses—immovable
Amphiarthroses—slightly movable
Diarthroses—freely movable
Three structural classifications of joint (based on
material binding bone together and whether a joint
cavity is present):



Fibrous
Cartilaginous
Synovial
(a)




Bones joined by dense regular connective tissue
(collagen fibers)
No joint space present
Most are immovable or slightly movable
Three types:




Sutures
Syndesmoses
Gomphoses
Suture
Joint held together with very short,
interconnecting fibers, and bone edges
interlock. Found only in the skull.
Suture
line
Fibrous Joints-Sutures
Rigid, interlocking joints containing short connective
tissue fibers (looks like a closed zipper)
 Movement depends on length of fibrous tissue connecting
the bones
 Allow for growth during youth
 In middle age, the fibrous connective tissue is replaced by
bone

Dense
fibrous
connective
tissue
Figure 8.1a
1
11/25/2015
(b) Syndesmosis
Joint held together by a ligament.
Fibrous tissue can vary in length, but
is longer than in sutures.



Bones connected by dense regular
connective tissue. This can either be
ligaments or interosseous membrane
Movement varies from immovable to
slightly movable
Examples:


Fibula
Tibia
Distal tibiofibular joint
Membrane connecting the radius and ulna
Ligament
Figure 8.1b
(c) Gomphosis
“Peg in socket” fibrous joint. Periodontal
ligament holds tooth in socket.


Peg-in-socket joints of teeth in alveolar
sockets
Fibrous connection between the bone and
tooth is the periodontal ligament
Socket of
alveolar
process
Root of
tooth
Periodontal
ligament
Figure 8.1c
2
11/25/2015



Articulating bones united by cartilage
No joint space and not highly movable
Two types:
Synchondroses
 Symphyses


Cartilaginous Joints: Synchondroses
A bar or plate of hyaline cartilage unites the bones
Immovable joints
 Most common is the epiphyseal plates in the long bones
of growing kids
 Another example is the immovable joint between the
costal cartilage of the first rib and the manubrium of the
sternum and the ribs and their costal cartilages


(a)
Synchondroses
Bones united by hyaline cartilage
Sternum
(manubrium)
Epiphyseal
plate (temporary
hyaline cartilage
joint)
Joint between
first rib and
sternum
(immovable)
Figure 8.2a




Hyaline cartilage covers the articulating
surfaces and is fused to an intervening pad of
fibrocartilage
Acts as a shock absorber, and permits a limited
amount of movement in the joint
Strong, flexible and slightly movable joint
Examples are intervertebral joints and the
pubic symphysis
(b)
Symphyses
Bones united by fibrocartilage
Body of vertebra
Fibrocartilaginous
intervertebral
disc
Hyaline cartilage
Pubic symphysis
Figure 8.2b
3
11/25/2015
All are diarthrotic (freely movable joint)
Include all limb joints; most joints of the body
•
•
Synovial Joints have specialized features:
Articular cartilage: hyaline cartilage
1.
•
Thin, spongy material cushions and absorbs
compression placed on joint so bone ends are not
crushed
Joint capsule:
2.
Outer two-layered fibrous capsule that surrounds and
strengthens bones so they are not pulled apart
• Outside layer made of dense irregular connective tissue
and inner synovial membrane is made of loose
connective tissue and covers all internal joint surfaces
•
Specialized features cont.:
3.
Synovial fluid:
•
•
•
Viscous slippery filtrate of plasma + weak acid
Occupies all free space within the joint capsule
Lubricates and nourishes articular cartilage. It also reduces the
friction between the cartilages and acts as a shock absorber.
Otherwise, the friction, heat, and stresses would destroy the
joint surfaces and tissues
4. Rich nerve and blood vessel supply:
•
•
•
•
Specialized Features Continued
5. Two possible types of reinforcing ligaments:
Nerve fibers detect pain, monitor joint position and stretch and
help maintain muscle tone
Stretching joints leads to nerve impulses that send signals to the
central nervous system which in turn create reflexive
contraction of muscles surrounding the joint
Capillary beds produce synovial fluid that is housed in the
joints by filtering the blood
Ligaments-dense regular connective tissue that connects one bone to
another
Intrinsic ligaments-ligaments that are embedded within the joint
capsule to provide structural strength
Extrinsic ligaments-ligaments not apart of the joint capsule. They
made be found inside or outside of the joint capsule
•
•
•
•
6. Tendons-dense regular connective tissue that connects
muscle to bone or muscle to some other structure
•
•
Tendons typically cross over or cross around a joint so when a
muscle contracts, the tendon tightens over or around the joint and
stabilizes the joint.
Example-Biceps brachii tendon crosses the shoulder joint, stabilizing
the head of the humerus in the glenoid cavity.
4
11/25/2015
Coracoacromial
ligament


Bursae and tendon sheaths are not a part of synovial
joints but they often as closely associated with the joints
Bursae:





Flattened, fibrous sacs lined with synovial membranes
Contain synovial fluid
Commonly act as “ball bearings” where ligaments, muscles, skin,
tendons, or bones rub together
They are found where ligaments, muscles, skin, tendons, or bones
rub together
Tendon sheath:


It is an elongated bursa that wraps completely around a tendon
that undergoes a lot of friction (bun around a hot dog)
They are found most often where several tendons are crowded
together in narrow canals like in the wrist and ankles
Subacromial
bursa
Cavity in
bursa containing
synovial fluid
Humerus
resting
Bursa rolls
and lessens
friction.
Humerus head
rolls medially as
arm abducts.
Humerus
moving
(b) Enlargement of (a), showing how a bursa
eliminates friction where a ligament (or other
structure) would rub against a bone
Figure 8.4b
Acromion
of scapula
Coracoacromial
ligament
Subacromial
bursa
Joint cavity
containing
synovial fluid
Fibrous
articular capsule
Tendon
sheath
Tendon of
long head
of biceps
brachii muscle

An inflammation of a bursa, usually caused by a
blow or friction
 Falling hard on your knee or leaning on your elbow
can damage the bursa
 Treated with rest and ice and, if severe, antiinflammatory drugs

Hyaline
cartilage
Synovial
membrane
Humerus

Fibrous
capsule
Bursitis
Tendonitis
Inflammation of tendon sheaths typically caused by
overuse
 The symptoms are pain and swelling and treatment
is similar to bursitis

(a) Frontal section through the right shoulder joint
Figure 8.4a
5
11/25/2015
Osteoarthritis
 Common, irreversible, degenerative (“wear-andtear”) arthritis
 85% of all Americans develop OA, more women
than men
 Probably related to the normal aging process
 More cartilage is destroyed than replaced in badly
aligned or overworked joints
 Exposed bone ends thicken, enlarge, form bone
spurs, and restrict movement
 Treatment: moderate activity, mild pain relievers,
capsaicin creams, glucosamine and chondroitin
sulfate
Rheumatoid Arthritis
 Chronic, inflammatory, autoimmune disease of
unknown cause
 Usually arises between age 40 and 50, but may occur
at any age; affects 3 times as many women as men
 Signs and symptoms include joint pain and swelling
(usually bilateral), anemia, osteoporosis, muscle
weakness, and cardiovascular problems

RA begins with synovitis of the affected joint



Inflammatory blood cells migrate to the joint, release
inflammatory chemicals
Inflamed synovial membrane thickens into a pannus (an
abnormal tissue that clings to articular cartilage)
Pannus erodes cartilage, scar tissue forms and scar tissue
eventually ossifies which immobilizes the joint
Figure 8.15
6
11/25/2015
Rheumatoid Arthritis: Treatment
 Conservative therapy: aspirin, long-term use of
antibiotics, and physical therapy
 Progressive treatment: anti-inflammatory
drugs or immunosuppressants
 New biological response modifier drugs
neutralize inflammatory chemicals-Enbrel,
Humira, Remicade
Gouty Arthritis
 Deposition of uric acid crystals in joints and
soft tissues, followed by inflammation











Due to compression and shear stress
Cartilage fragments left behind may cause joint to lock or bind
Cartilage rarely repairs itself because it is avascular
Repaired with arthroscopic surgery (small instrument with fiber
optic light and small incisions through which to work)
Torn
meniscus
Dislocations





The ligaments are stretched or torn
Partial tears slowly repair themselves
Complete ruptured ligaments require prompt surgical repair
Cartilage tears


More common in men
Typically affects the joint at the base of the
great toe
In untreated gouty arthritis, the bone ends fuse
and immobilize the joint
Treatment: drugs, plenty of water, avoidance of
alcohol
Sprains


Either excessive uric acid or kidneys are not
excreting it fast enough)
Occur when bones are forced out of alignment
Accompanied by sprains, inflammation, and joint immobilization
Caused by serious falls or playing sports
Once you have done it, the joint is somewhat stretched out so it can easily happen
again
Subluxation—partial dislocation of a joint
Figure 8.14
7