Download Bone disorders and diseases

Developmental Aspects: Fetal Skull
• Infant skull has more bones than the adult skull
• Skull bones such as the mandible and frontal bones are unfused
• At birth, skull bones are connected by fontanelles
• Fontanelles
• Unossified remnants of fibrous membranes between fetal skull bones
• Four fontanelles
• Anterior, posterior, mastoid, and sphenoid
Frontal bone
Ossification
center
Posterior fontanelle
(a) Superior view
Parietal bone
Ossification
center
Posterior
fontanelle
Mastoid
fontanelle
(b) Lateral view
Frontal suture
Anterior
fontanelle
Parietal bone
Occipital bone
Frontal bone
Sphenoidal
fontanelle
Temporal bone
(squamous portion)
Occipital bone
Figure 7.35
Developmental Aspects: Growth Rates
• At birth, the cranium is huge relative to the face
• At 9 months of age, cranium is ½ adult size
• Mandible and maxilla are foreshortened but lengthen with age
• The arms and legs grow at a faster rate than the head and trunk,
leading to adult proportions
Developmental Aspects: Spinal Curvature
• Thoracic and sacral curvatures are obvious at birth
• These primary curvatures give the spine a C shape
• Convex posteriorly
Figure 7.37
Developmental Aspects: Spinal Curvature
•Secondary curvatures
•Cervical and lumbar—convex anteriorly
•Appear as child develops (e.g., lifts head,
learns to walk)
Developmental Aspects: Old Age
• Intervertebral discs become thin, less hydrated, and
less elastic
• Risk of disc herniation increases
• Loss of stature by several centimeters is common by
age 55
• Costal cartilages ossify, causing the thorax to become
rigid
• All bones lose mass
Ankylosing spondylitis
•The cause of ankylosing spondylitis is
unknown, but genes seem to play a role.
•The disease most often begins between
ages 20 and 40, but it may begin before age
10. It affects more males than females.
Medial tibial stress syndrome (MTSS),
tibial periostitis or shin splints
• pain associated with MTSS is caused from a
disruption of Sharpey's fibers that connect the
medial soleus fascia through the periosteum of
the tibia where it inserts into the bone
Stress Fractures
•Stress fractures are tiny cracks in a bone.
Stress fractures are caused by the repetitive
application of force, often by overuse —
such as repeatedly jumping up and down or
running long distances.
*Disorders associated with Homeostatic
Imbalances
• Osteomalacia and rickets
• Calcium salts not deposited
• Rickets (childhood disease) causes bowed legs and
other bone deformities
• Cause: vitamin D deficiency or insufficient dietary
calcium
Rickets
*Disorders associated with Homeostatic
Imbalances
• Osteoporosis
• Loss of bone mass—bone resorption outpaces deposit
• Spongy bone of spine and neck of femur become most
susceptible to fracture
• Risk factors
• Lack of estrogen, calcium or vitamin D; petite body form;
immobility; low levels of TSH; diabetes mellitus
Figure 6.16
*Osteoporosis: Treatment and Prevention
• Calcium, vitamin D, and fluoride supplements
•  Weight-bearing exercise throughout life
• Hormone (estrogen) replacement therapy (HRT) slows bone loss
• Some drugs (Fosamax, SERMs, statins) increase bone mineral density
*Paget’s Disease
• Excessive and haphazard bone formation and breakdown, usually in
spine, pelvis, femur, or skull
• Pagetic bone has very high ratio of spongy to compact bone and
reduced mineralization
• Unknown cause (possibly viral)
• Treatment includes calcitonin and biphosphonates
Rheumatoid Arthritis (RA)
• 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
• Pannus erodes cartilage, scar tissue forms, articulating bone ends connect
(ankylosis)
• Conservative therapy: aspirin, long-term use of antibiotics, and physical
therapy
• Progressive treatment: anti-inflammatory drugs or immunosuppressants
Osteoarthritis (OA)
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Common, irreversible, degenerative (“wear-and-tear”) 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
Common, irreversible, degenerative (“wear-and-tear”) arthritis
85% of all Americans develop OA, more women than men
Probably related to the normal aging process
Developmental Aspects of Bones
• Embryonic skeleton ossifies predictably so fetal age easily determined
from X rays or sonograms
• At birth, most long bones are well ossified (except epiphyses)
Parietal bone
Occipital bone
Mandible
Frontal bone
of skull
Clavicle
Scapula
Radius
Ulna
Ribs
Humerus
Vertebra
Ilium
Tibia
Femur
Figure 6.17