Topic 9: Skeletal System - Bone Growth (postnatal) Flashcards
What is bone growth in length?
- endochondral growth at epiphyseal plates
How does bone grow in length? (2)
- cartilage grows and matrix near diaphysis becomes bone
- growth in length stops when epiphyseal plate ossifies into epiphyseal line (closure)
What is bone growth in diameter called?
- appositional growth
aka bone remodelling
How does bone grow in diameter? (2)
- osteoblasts beneath periosteum secrete bone matrix (external bone surface)
- osteoclasts resorb bone on the endosteal surface
- then size of cavity keeps place with growing bone
think outside is growing and inside is taking it away??
What are 3 factors affecting bone growth/remodelling?
- mechanical stress
- Nutrition
- Hormones
How does mechanical stress affect bone growth? Use execise, injury, and weights/electric currents as an example
- due to muscle action
1. Moderate exercise increases osteblast activity in areas of stress (more building than breakdown)
2. Injury that restricts movement decreases osteoblast activity and no change in osteoclast activity decreases bone mass
3. Weights or electric currents may speed healing by increasing osteoblast activity
Which vitamins and minerals are needed for nutrition of bones? (4)
Ca2+ and PO4-
Vitamin C and D
Why do we need Ca2+ and PO4-?
required for bone matrix production
Why do we need vitamin C?
- for collagen production
Why do we need vitamin D? (2)
- increase absorption of calcium from intestine
- lacking vit D causes rickets (soft bones)
Which hormones are needed for bone growth/remodelling? (5)
- GH
- thyroid
- E and Testosterone
- Calcitonin
- PTH
Why do we need GH and Thyroid hormone?
stimulate bone growth
Why do we need estrogen and testosterone for bones? (2)
- increases ostebclast activity
- Estrogen (both sexes) helps ossification of epiphyseal plate (to line)
What is the function of calcitionin? (2)
- inhibits osteoclast activity
- increases calcium movement from blood to bone to promote bone growth
What is the function of PTH?
- Increases osteoclast activity and decreases osteoblast activity to increase blood calcium
What is osteoporosis?
- decrease in bone mass
What are the risk factors to osteoporosis (7)
- increasing age (decrease in sex hormones)
- post menopause (decrease E)
- inadequate diet (decreased vit D, Ca2+)
- illness, excess PTH
- too little/excessive exercise (stress - cortisol)
- Drugs like cortisone and alcohol (decreases osteoblast activity)
- smoking (decreases E)
What is the process for bone repair? (3)
1) begins with formation of a blood clot
2) replaced by a callus
3) callus ossifies - both intramembranous and endochondral
What is a callus made of?
- fibrous network and fibrocartilage isletsq
How long does bone repair take? (2)
4-6 weeks (depends on age and diet)
- cast required since movement can refracture new matrix
