The skeletal system document summarizes key aspects of bone structure and function. It describes how bone is composed of mineral and organic components including collagen fibers. It discusses how aging affects bone remodeling and loss of bone density. It also outlines interventions that can help slow bone loss such as hormone therapy, medications, diet and exercise. Diagrams illustrate bone density changes with aging and risks of fracture.

1. Skeletal System

3. A femur head with a cortex of compact
bone and medulla of trabecular bone

5. Spongy Bone

8. Pictures of
Healthy &
Unhealthy
Bone

10. Osteoporosis is accelerated bone loss. Normally, there is loss of bone mass with aging, perhaps 0.7% per year in
adults. However, bone loss is greater in women past menopause than in men of the same age. The process of bone
remodeling from resorption to matrix synthesis to mineralization normally takes about 8 months--a slow but
constant process. Bone in older persons just isn't as efficient as bone in younger persons at maintaining itself--there
is decreased activity of osteoblasts and decreased production of growth factors and bone matrix. (Sambrook and
Cooper, 2006)
This diagram illustrates changes in bone density with aging in women. The normal curve (A) steepens following
menopause, but even by old age the risk for fracture is still low. A woman who begins with diminished bone
density (B) even before menopause is at great risk, particularly with a more accelerated rate of bone loss.
Interventions such as postmenopausal estrogen (with progesterone) therapy, the use of drugs such as the non-
hormonal compound alendronate that diminishes osteoclast activity, and the use of diet and exercise regimens
can help to slow bone loss (C) but will not stop bone loss completely or restore prior bone density. Diet and
exercise have a great benefit in younger women to help build up bone density and provide a greater reserve
against bone loss with aging. (Winslow et al, 2009)

12. Bone is made of mineral
+ organic (mainly collagen)
components
Treated with hydrochloric acid
to dissolve mineral
leaves collagen component intact
Treated with bleach (hypochlorite)
to digest collagen
leaves mineral component intact
Collagen shrinkage
on drying

13. osteocytes

14. osteocytes

15. Osteoclast….munching away!

16. Osteoblasts laying down new bone matrix (on an artificial framework).

17. osteoblast

18. Scanning electron microscopy image of the bone-cotton after immersion in simulated body
fluid showing the formation of hydroxyapatite on the surface of the fibers.

19. A bat skeleton at day 80 of
embryonic development. Bone
appears in red and cartilage in
blue.

20. Skeleton of a 16 week old human fetus.
Hardened bone appears yellow here. Gaps
between the ends of bones, such as the ribs
and spinal column, are filled with cartilage (not
seen) that forms a matrix upon which hard
bone forms. The pelvis (lower centre) and right
leg (lower right) are seen. At this stage of
development the foetus weighs 200 grams and
has a crown-rump length of up to 14
centimetres. Stained with Alizarin red dye.

21. Lateral view
Medial view
These are 2 views of the same 12 week 92 mm CRL human fetus head, double stained to show
both cartilage (blue) and newly-formed bone (red). The head undergoes two different forms of
ossification (endochondral and intramembranous) in separate regions of the skull.

23. Endochondral ossification of a long bone

24. Note the oblique minimally
displaced distal radial
fracture, which extends to
the growth plate and then
laterally along the plate.

25. Salter Harris Type I Fracture (along growth plate)

26. Epiphyseal plate…

27. Epiphyseal plate…

28. magnified

29. Parts of an epiphyseal plate…

30. Fetal skull

31. C-shaped spine of a newborn

33. fibrous

34. cartilaginous

35. synovial

37. Open fracture

38. Compression fracture

39. Point-to-Ponder
1. The tensile strength of bone (resists pulling forces) is due to:
a. Osteoblasts
b. Mineral salts
c. Collagenous fibers
2. The compressional strength (resist crushing) of bone is due to:
a. Osteoblasts
b. Mineral salts
c. Collagenous fibers
3. In aging, less collagen is deposited in bone tissue, so that more
of the bone is composed of mineral salts. Predict the effect of
these changes on a bone’s ability to resist the forces that cause a
bone to break.
3. The bone to the right…
a. Has been demineralized.
b. Has had its organic components removed.

40. Point-to-Ponder
Predict the flow of a nutrient from circulation to
an osteocyte. List 5 structures.

41. Point-to-Ponder
A 15-year old football player is tackled during a
game and the distal epiphyseal plate of the
left femur is damaged.
a. His left lower limb will not grow.
b. His left thigh will not grow.
c. His left thigh will be shorter than his right
thigh.
d. Recovery will be difficult.

42. flexion

43. extension

44. hyperextension

45. dorsiflexion

46. plantar flexion

47. pronation

48. supination

49. abduction

50. adduction

51. inversion

52. eversion

53. rotation

54. circumduction