Midterm - Lecture 9 Flashcards
What grows at the physe?
long bone
How does long bone grow at the physe?
- Cartilage cells undergo proliferation, hypertrophy, and programmed cell death causing provisional calcification of cartilage cells
- Invasion of calcified cartilage by blood vessels is accompanied by movement of osteoblasts into area from meta physis
- Resorption of calcified cartilage followed by laying down of bone matrix – calcified primary bone
What happens to bone growth with an animal that has rickets?
failure to mineralize growth plates of the bone
rubbery widened cartilage remains which makes bones bendable
What is the cause for rickets?
can be due to calcium deficiency but more commonly die to vitamin D or phosphate deficiency
What happens within the bone with an animal that has rickets?
the hypertrophic cartilage cells fail to undergo apoptisis eventually undergo necrotic death
zone of calcified cartilage fails to calcify
Why can piglets get rickets?
poor transfer of vitamin D across the placenta and there is little to no Vitamin D in milk
What happens within the bone with an animal that has osteomalacia?
during the reversal phase of bone remodeling the newly laid down matrix fails to mineralize
What are the phases of remodeling?
activation, resorption, and reversal
What occurs during the activation phase of remodeling?
osteoblasts retract from the surface of the area of bone to be remodeled, osteoclasts move toward the site of exposed bone
What occurs during the resorption phase of remodeling?
- Osteoclasts develop a ruffled border and form a tight seal with the exposed bone
- Secretion of acids and enzymes cause dissolution of the organic matrix freeing the minerals which enter extracellular fluid
- Osteoclasts scoop out bone matrix and mineral to a depth of approximately 50 microns
What occurs during the reversal phase of remodeling?
- Osteoclasts leave the area and become inactive
- Osteoblasts from among the endosteal bone lining cells at the edge of the resorption site now enter the depths of the resorption cavity
- Osteoblasts begin producing new bone matric to fill in the resorption cavity; Some become trapped within the matrix to give rise to new osteocytes
When does osteoporosis occur?
when the diet fails to supply calcium
How does osteoporosis affect bone remodeling?
the low supply of calcium causes a disconnect between the resorption phase
How does lactational osteoporosis affect bone remodeling?
the need for calcium to support lactation causes a disconnect between the resorptive and reversal phases of the remodeling process
the resorbed bone is not replaced
How does the body respond to nutritional secondary hyperparathyroidism?
- Increases renal reabsorption of Ca; Only a limited amount of Ca can be recovered
- Increases osteoclastic bone resorption; Resorption and bone formation uncoupled, eventually reduces bone calcium content
- Increases production of vitamin D
