Download Bones and Bone Tissue

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Bones and Bone Tissue
Reading: Chapter 6
Bone Functions:
Typical Bone (Overhead -real bone)
1) diaphysis - tubular shaft
2) epiphysis - each end 3) metaphysis (if growing)
4) Cavities
5) periosteum -
Mature Bone Bone Cells
1) Osteogenic
2) Osteoblasts
3) Osteocytes
4) Osteoclasts
Bone Development (early)
Mesoderm
Somites - 3 parts -
1) Endochondral (overhead)
a) 6 weeks of age - embryonic mesenchyme tissue ---->
b) ---> invaded by blood vessels
c) Ossification begins here (----> bone collar)
Process (many steps)
d) 3-4 months
e) ~ age 17 - no new cartilage cells produced
f) ~ age 25 - bone growth stops
Lateral growth
After Birth to 5 years - Longitudinal Growth (many steps)
4 zones of cartilage
2 zones of bone
2) Intramembranous Ossification
(process - many steps)
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Mature Bone Tissue
- v. flexible - Collagen and G.S.
- rigidity from inorganic salts
Compact Bone
• Actually: osteons
• lacunae
Spongy Bone
- tiny spikes of calcified bone -trabeculae
Most Bones
- outer shell of compact bone
- inner layer of spongy
Homeostasis - or "Bones are Dynamic"
A. Modeling - draw
B. Remodelling
4 Examples
C. Factors Affecting Bone Dev, Growth, Repair
1) Vitamins D, A, C
2) Hormones
A. Pituitary (in Sella Turcica)
B. Ovaries and Testes
Fracture and Repair (Overhead)
1) Blood vessels torn
2) Capillaries invade clot - next several weeks
3) Procallus formed - connective tissue - 3-4 weeks or so
4) Callus (soft fibrocartilage ---> hard spongy bone --> harder compact)
5) Remodelling later
Physiological Functions of Bone
1) Ca+2 Levels
A. Blood levels low
--> parathyroid glands --> parathyroid hormone (PTH)
1) stimulates osteoclast activity --> (Ca+2 released into blood)
2) kidneys incrretain Ca+2 (and excrete PO4)
B. Blood levels high
thyroid gland --> calcitonin (32 a.a. protein)
---> lowers Ca+2 levels by
1) inhibiting osteoclasts
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2) stimulating urinary secretion of Ca+2 (inhibiting re-uptake)
2) PO4-3
3) Blood Cells - Red Marrow
Aging
1) Osteoporosis common esp in women
WOMEN - After 30 (30% loss by age 70)/ MEN - after 60
can be hastened by (several factors)
can be avoided by (factors)
2) Loss of height
caused by vertebrae and disk mass loss
Exercise
• incr physical stress --->
• decr physical stress