2. 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

3. Frontal suture Frontal bone Anterior fontanelle Ossification center
Parietal bone
Posterior fontanelle
Occipital bone
(a) Superior view
Parietal bone
Frontal bone
Ossification
center
Sphenoidal
fontanelle
Posterior
fontanelle
Temporal bone
(squamous portion)
Mastoid
fontanelle
Occipital bone
(b) Lateral view
Figure 7.35

4. 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

5. Developmental Aspects: Spinal Curvature
Thoracic and sacral curvatures are obvious at birth
These primary curvatures give the spine a C shape
Convex posteriorly

6. Figure 7.37

7. Developmental Aspects: Spinal Curvature
Secondary curvatures
Cervical and lumbar—convex anteriorly
Appear as child develops (e.g., lifts head, learns to walk)

8. 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

9. 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.

13. 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

15. 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.

19. *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

20. Rickets

21. *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

22. Figure 6.16

23. *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

24. *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

29. 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

32. Osteoarthritis (OA)
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

37. 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)

38. Parietal bone Occipital bone Frontal bone of skull Mandible Clavicle
Scapula
Radius
Ulna
Ribs
Humerus
Vertebra
Ilium
Tibia
Femur
Figure 6.17