Ch 6, 6 bone homeostasis

Question 1

remodeling of bones

Answer 1

occurs throughout lifetime

a. in response to mechanical stress, damage and hormonal levels
b. variations in blood calcium levels

Question 2

bone deposit

Answer 2

a. occurs where bone is injured or added strength is needed

b. requires a diet rich in protein; vitamin C, D and A; calcium; phosphorus, magnesium and manganese

Question 3

bone resorption

Answer 3

occurs where there is a reduction in mechanical stress
increases with aging
a. Osteoclasts secrete
–lysosomal enzymes (digest organic matrix)
–acids (convert calcium salts into soluble forms)
b. dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood

Question 4

control of remodelling

Answer 4

a. hormonal mechanisms that maintain calcium homeostasis in the blood-negative feedback loop
b. response to mechanical stress

Question 5

hormonal control of blood calcium

Answer 5

a. blood calcium is necessary for..
- transmission of nerve impulse
- muscle contraction
- blood coagulation
- secretion by glands and nerve cells
- cell division

b. role of parathyroid hormone(PTH)
-decrease blood calcium
-parathyroids release PTH
-PTH stimulates osteoclasts to degrade bone matrix
-calcium released into blood
-increase in blood calcium
++if blood calcium is low, skeletal calcium is sacrificed tosatisfy other needs of the body

Question 6

response to mechanical stress

Answer 6

a. a bone grows or remodels in response to forces or demands placed upon it
b. curved bones are thickest where they are most likely to buckle
c. trabeculae form along lines of stress
d. large, bony structures occur where heavy, active muscles attach

Question 7

classification of bone fractures

Answer 7

1. position of bone ends after fracture
   - non displaced-ends remain normal position
   - displaced-ends out of normal alignment
2. completeness of break
   - complete-broken all the way through
   - incomplete-not broken all the way through
3. orientation of the break on the long axis of bone
   - linear- parallel to the long axis
   - transverse- perpendicular to long axis
4. whether or not the bone ends penetrate the skin
   - compound (open)-bone ends penetratethe skin
   - simple (closed) -bone ends do not penetrate the skin

Question 8

stage 1; bone healing

Answer 8

hematoma forms

a. torn blood vessels hemorrhage
b. clot forms
c. site becomes swollen, painful and inflamed

Question 9

stage 2

Answer 9

fibrocartilaginous callus forms

a. phagocytic cells clear debris
b. osteoblasts begin forming spongy bone after one week
c. fibroblasts secrete collagen fibers to connect bone ends
d. mass of repair tissue now called fibrocartilaginous callus

Question 10

stage 3

Answer 10

bony calls forms

a. new trabeculae form a bony, hard callus
b. bony callus formation continues until firm union is formed in about 2 months

Question 11

stage 4

Answer 11

bone remodeling

a. in response to mechanical stressors over several months
b. final structure resembles original