1. But first let’s see if this helps…
Bone Metabolism
Notes in Notebook
But first let’s see if this helps…
Bob and Claude???

2. Bone Metabolism Bone stores 99% of total calcium in body
Calcium ions involved with many body systems
nerve & muscle cell function
blood clotting
enzyme function in many biochemical reactions

3. Bone Homeostasis/Metabolism

4. Details…Details… G proteins (guanine nucleotid -binding proteins)
 G-protein activates
adenylate cyclase to
convert ATP to
cAMP in the cytosol
G proteins
(guanine nucleotid
-binding proteins)
Proteins involved in transmitting
chemical signals outside the cell,
and causing changes inside the cell
They communicate signals from
many hormones,
neurotransmitters,
and other signaling factors

5. Bone Metabolism Background Info
The thyroid gland is located in the front of the neck and wraps around the trachea; has a shape that is similar to a butterfly formed by two wings (lobes) and helps to regulate metabolism

6. Bone Metabolism Hormones
*Parathyroid hormone (PTH) is secreted if Ca+2 levels falls
PTH gene is turned on and more PTH is secreted from gland
osteoclast activity increased
kidneys retain Ca+2 so it is not all lost in urine and produces calcitriol
*Calcitriol is a hormone that works with PTH & promotes absorption of calcium in digestive tract & blood

7. Bone Metabolism Hormones
*Calcitonin is a hormone that produces the opposite effects:
if calcium level gets too high
less absorption in the digestive tract,
increased excretion by the kidneys,
movement of calcium from the blood into the bones
inhibits osteoclast activity
increases bone formation by osteoblasts

8. CONTINUED NOTES in Notebook: Important Bone Metabolism Vitamins
Vitamin A:
Necessary for osteoclast activity
Vitamin C:
Needed to build durable bone matrix (osteoid)
Vitamin D:
Calcitriol is formed from vitamin D

9. Bone Homeostasis Bone Tissue and Exercise
Pull on bone by skeletal muscle and gravity is mechanical stress.
Lack of mechanical stress results in bone loss
reduced activity while in a cast or bedridden person
Weight-bearing exercises build bone mass

10. Osteoporosis Prevention (or decrease in severity)
Calcium supplements, weight-bearing exercise, & hormone replacement therapy (including a form of calcitonin)
behavior when young may be most important factor!

11. Bone Remodeling Ongoing process
Osteoclasts secrete enzymes and acids to break down bone
This releases calcium and other minerals of bone for resorption by blood
Osteoblasts rebuild osteons

12. Bone Remodeling
Continual remodeling of bone matrix along lines of mechanical stress
The distal femur is fully remodeled every 4 months

13. Fracture Repair A fracture is break in a bone STAGE 1 Inflammation)
Repair starts with formation of fracture hematoma: damaged blood vessels produce clot, bone cells die
new capillaries grow into damaged area
STAGE 2 Repair)
Callus (healing tissue) formation:
fibroblasts lay down collagen fibers
chondroblasts produce cartilage to span the broken areas of the bone

14. Fracture Repair Bone Formation: Bone remodeling:
osteoblasts secrete spongy bone that joins the broken areas of bone
lasts 3-4 months
Bone remodeling:
compact bone replaces the spongy in the callus
surface is remodeled back to normal shape

15. Video Clip Principles of Fracture Healing