a presentation about bone growth and factors affecting bone growth

1. BONE GROWTH & FACTORS
AFFECTING BONE GROWTH

2. BONE
 A bone is a rigid organ that constitutes part of the vertebrate skeleton.
 produce red and white blood cells, store minerals, provide structure and support
for the body, and enable mobility.
 Bones support and protect the various organs of the body.

3. COMPOSITIONAL CLASSIFICATION
 COMPACT BONE:
Mostly solid matrix cells. It does not contain marrow.
 SPONGY BONE:
Consist of a lacy network of bone with many small, marrow filled spaces.
 COMPOSITION OF BONE:
 BONE MARROW:
YELLOW MARROW – fats
RED MARROW – blood forming cells
 MATRIX:
 A bonding of multiple fibers & chemicals of different materials.
 Primarily Collagen Fibers & Crystalline Salts.

4. GROWTH AND DEVELOPMENT
 OSSIFICATION:
The term Orthogenesis and Ossification are often used
synonymously to indicate the process of bone formation
 TYPES OF OSSIFICATION:
There are two types of Ossification:
 Pre-natal Ossification
 Post-natal Ossification

5. PRE-NATAL OSSIFICATION
 PRE-NATAL OSSIFICATION:
 The type of ossification that occurs during embryonic development of fetus.
It is sub-divided into following types:
 1.Intramembranous ossification.
 2. Endochondral ossification.

6. INTRAMEMBRANOUS OSSIFICATION:
 Intramembranous ossification mainly occurs during the formation of the flat
bones of the skull and some others.
 The bone is formed from connective tissue such as mesenchyme tissue(formed
during embryogenesis) rather than from cartilage.

7. steps in intramembranous ossification
 Development of ossification center:
 Condensation of mesenchymal tissue and appearance of ossification center
 Calcification
 Calcium and other mineral salts (Phosphorous & Magnesium salts) are deposited
and extracellular matrix calcified (harden)

8.  Formation of trabeculae:
 Ossification centers fuses to form trabeculae.
 Blood vessels grow in between.
 Development of periosteum:
 Mesenchyme at the periphery of bone develops into periosteum.

9. ENDOCHONDRAL OSSIFICATION
 Primary ossification:
 Endochondral ossification begins with points in the cartilage called “Primary
ossification centers”.
 They mostly appear during fetal development, though a few short bones begin
their primary ossification after birth.
 These cartilage points are responsible for the formation of the diaphysis of long
bones, short bones, and certain parts of irregular bones.
 Begins at 8weeks of development.

10.  SECONDARY OSSIFICATION:
 Secondary ossification occurs after birth and forms the EPIPHYSES of long
and the extremities of irregular and flat bones.
 The diaphysis and both epiphyses of a long bone are separated by a growing
of cartilage(the epiphyses plate). When the child reaches skeletal maturity (18 to
25 years of age), all cartilage is replaced by bone, fusing the diaphysis and both
epiphyses together (epiphyseal closure).
 Begins 2nd month of development

11. BONE REMODELING AND REPAIR
 POST NATAL OSSIFICATION:
The type of ossification that occurs after birth up to adulthood.
 DEFINITION:
o Bones can grow throughout life to respond to stress by changing size , shape
and strength called BONE REMODELING and BONE REPAIR
o Bone renewal continues after birth into childhood.
o Bone remodeling is the replacement of the old bone tissues by new bone
tissues.

12.  BONE CELLS
Three types of cells are involved in bone remodeling.
OSTEOBLAST: Bone-forming cell
OSTEOCYTES: Mature bone cell
OSTEOCLAST: Bone-destroying cell

13. STAGES OF BONE REPAIR
 HEMATOMA FORMATION:
o Bone breaks, blood vessels are torn and hemorrhage.
o Mass of clotted blood forms at fracture site.
o Bone cells are deprived of nutrition and die.
o Tissue at fracture site becomes swollen, painful and inflamed.
 BONE GENERATION:
o Within the days of fracture, capillaries grow into hematoma, while phagocytic
cells(eating) begin to clear away the dead cells.
o Though the fragments of blood clot may remain, Fibroblast and osteoblasts begin to
reform bone.

14. o Fibroblast produce collagen fibers that connect the broken ends.
o Osteoblasts begin to form spongy bone.
o The repair tissue between the broken bone ends is composed of both hyaline and
fibrocartilage. Some bone spicules(the bony matrix) may also appear at this point.
 3.BONY CALLUS FORMATION:
o The fibro cartilaginous callus is converted into bony callus of spongy bone.

15. o It takes about two months for the broken bone ends to be firmly joined together
after the fracture.
o It is similar to endochondral formation of bone when cartilage becomes ossified.
 4.BONE REMODELING:
o The bony callus is then remodeled by the osteoclast and osteoblasts, with excess
material on the exterior of bone and within the medullary cavity being removed.

16. o Compact is added to the create bone tissue that is similar to the original,
unbroken bone.
o This remodeling can take many months; the bone may remain uneven for years.

17. Factors Affecting Bone Growth and Bone
Remodeling
 Normal bone metabolism depends on several factors
 Minerals
 Large amounts of calcium and phosphorus and smaller
amounts of magnesium, fluoride, and manganese are required
for bone growth and remodeling
 Vitamins
 Vitamin A stimulates activity of osteoblasts
 Vitamin C is needed for synthesis of collagen
 Vitamin D helps build bone by increasing the absorption of
calcium from foods in the gastrointestinal tract into the blood
 Vitamins K and B12 are also needed for synthesis of bone
proteins

18.  Hormones
 During childhood, the hormones most important to bone growth are
growth factors (IGFs), produced by the liver and bone tissue (under
influence of hGH)
 IGFs stimulate osteoblasts, promote cell division at the epiphyseal plate, and
enhance protein synthesis
 Thyroid hormones (T3 and T4) also promote bone growth by
osteoblasts
 Insulin promotes bone growth by increasing the synthesis of bone
proteins

19.  Hormones
Estrogen and testosterone cause a dramatic effect on bone
growth
Cause of the sudden “growth spurt” that occurs during the teenage
year
Promote changes in females, such as widening of the pelvis
Ultimately-Shut down growth at epiphyseal plates
Parathyroid hormone, calcitriol, and calcitonin are other
hormones that can affect bone remodeling

20. Bone’s Role in Calcium Homeostasis
 Bone is the body’s major calcium reservoir
 Levels of calcium in the blood are maintained by controlling
the rates of calcium resorption from bone into blood and of
calcium deposition from blood into bone
 Both nerve and muscle cells depend on calcium ions (Ca2+)
to function properly
 Blood clotting also requires Ca2+
 Many enzymes require Ca2+ as a cofactor

21. Bone’s Role in Calcium Homeostasis
Actions that help elevate blood Ca2+ level
Parathyroid hormone (PTH) regulates Ca2+
exchange between blood and bone tissue
PTH increases the number and activity of osteoclasts (i.e.,
resorption)
PTH acts on the kidneys to decrease loss of Ca2+ in the urine
PTH stimulates formation of calcitriol (active form of Vitamin D) a
hormone that promotes absorption of calcium from foods in the
gastrointestinal tract

22. Physical factors
 FEASEABLE EXERCISE:
o Simple aerobic exercises like walking, jogging, and running could provide an
important role in maintaining and/or increasing bone density.
o For these reason walking could be an approach to prevent osteoporosis and
maintain bone mass.
 Effect of Gravity
o Pull of gravity and muscles Activate osteoblasts
o If not active , activates osteoclasts-atrophy
For example bones of SEA Divers are more stronger due to pull of gravity

23.  Exposure to sunlight:
Exposure of skin to ultraviolet portion of sunlight is favorable to bone development
because the skin can produce vitamin D when it is exposed to such radiation which
in turn plays an important role in bone development

24. NUTRITION
 PHOSPHORUS:
o A major mineral crystal in the body’s bone.
o phosphorus is found in dairy products and meat.
 MAGNESIUM:
o Primarily found in mineral crystals, magnesium improves bone strength.
o Older adults are more likely to be deficient in magnesium.

25.  VITAMIN A:
o Necessary for cells to differentiate normally and for normal skeletal growth and
also extremely important for eye health.
 VITAMIN K:
o Necessary for bone formation and mineralization, blood clotting, and may assist
transportation of calcium directly to the bone rather than the blood vessels