Bone Growth & Development

1. Bone Growth & Development

2. General Features

3. Long Bone
Longer than they are wide
Consists of diaphysis
(central shaft) & Epiphysis
(two ends)
Epiphysial plate – for
growing bones
Epiphysial line – when
growth stops

4. Short Bone
Approx. as broad as they
are long
Examples: wrist & ankle
bones

5. Flat Bones
 Have a relatively thin,
flattened shape
Examples: certain skull
bones, ribs, scapulae, and
sternum

6. Irregular Bones
 Bones not included in the
previous categories
Vertebrae and facial
bones

7. Histological Structure

8. Cells
Osteocyte – mature bone cell, enclosed in
lacuna
Osteoblast – bone-forming cell; secretes
collagen fibers and calcium salts of bone
tissue
Osteoclast – bone-destroying cell; breaks
down ECM to release calcium into the
bloodstream

9. O S T EB B LA
O
ST
A
G
O
C
O S T E O C LA
ST
R
A

10. Compact Bone
Mostly solid
matrix cells
Spongy Bone
Consists of a
lacy network
of bone wit
many small,
marrow filled
spaces

11. Marrow
Yellow marrow – fat
Red marrow – blood
forming cells

12. Matrix
 A bonding of
multiple fibers and
chemicals of different
materials
 Primarily collagen
fibers and crystallin
e salts

13. Matrix
The crystalline salts deposited in the matrix
of bone are composed principally
of calcium and phosphate, which are
combined to form hydroxyapatite crystals.
Calcium (Ca), phosphate (PO4), and hydroxide
(OH)
Ca10[PO4]6[0H]2

14. Growth &
Development

16. Pre-natal Ossification
1. Intramembranous
2. Endochondral
Bone develops from
Bone develops from
fibrous membrane
hyaline cartilage
Forms bones of skull and Forms all bones below
clavicle (all flat bones)
base of skull
Begins at 8 weeks of
Begins 2nd month of
development
development

23. Nutrition
Hormonal
secretions
Physical
exercise
Factors
for bone
development

24. Nutrition

25. Calcium
Makes up 2% of body weight
99% Stored in bones
A narrow range of 9-11 mg Ca/100 ml
blood maintained at all times.
Bone remodeling - key in maintaining
proper blood calcium levels

26. Calcium
1% Constant supply of Ca2+ in the blood
stream needed for:
◦Transmission of nerve impulses
◦Muscle contraction
◦Blood coagulation
◦Cell division

27. Phosphorus
A major mineral in the body's bone crystal,
phosphorus is found in dairy products and
meat.

28. Magnesium
Primarily found in bone crystals,
magnesium improves bone strength.
Older adults are more likely to be deficient
in magnesium.
Calcium supplements that contain
magnesium can help.

29. Vitamin K
Necessary for bone formation and
mineralization, blood clotting, and may
assist in channelling calcium directly to the
bone rather than the blood vessels.

30. Vitamin C
Collagen is the main protein in bone, and
Vitamin C is necessary for collagen
synthesis.
Vitamin C is present in citrus fruits and
tomatoes and in many vegetables.

31. Vitamin A
Necessary for cells to differentiate
normally and for normal skeletal growth,
and also is extremely important for eye
health.
Too little vitamin A is a major cause of
blindness worldwide.
Too much vitamin A can cause bone loss
and increase the risk of hip fracture.

32. Vitamin D
Vitamin D is necessary for the proper
absorption of calcium in the small intestine.

33. Physical exercise

34. Physical exercise
◦Pull of gravity & muscles
◦Activates osteoblasts
◦If not active, activates
osteoclasts - atrophy

35. Exposure to sunlight

36. Exposure to sunlight
Exposure of skin to the
ultraviolet portion of sunlight is
favorable to bone
development, because the skin
can produce vitamin D when it
is exposed to such radiation.

37. Hormones

38. Hormones
Pituitary Gland
Thyroid gland
Parathyroid glands
Ovaries and testes

39. Growth Hormone (Somatotropin)
From: Pituitary gland Other fx
 stimulates bone and
Stimulates activity in muscle growth
the epiphyseal platesmaintains the normal rate of
protein synthesis in all body
Main regulator of
cells
height
speeds the release of fats
as an energy source for
growth

40. Parathyroid Hormone
From: Parathyroid glands

41. Parathyroid Hormone
Low blood calcium
Releases PTH
Stimulates osteoclasts
to break down
bone tissue, and as a
result, calcium salts are
released into the blood.

42. Calcitonin
From: Thyroid gland

43. Calcitonin
Blood calcium level is
excessively high
Releases calcitonin
Inhibits osteoclast
activity allowing
osteoblasts to form bone
tissue. The excessive
calcium is stored in matrix.

44. Sex Hormones
↑ - Hinders osteoclast
production
↓ - Increased cytokines,
Increast osteoclast

45. Sex Hormones
Aging
Hypogonadism
-Diminished functional
activity of the gonads
-Hypoandrogenism &
Hypoestrogenism