Bone (Nishi) Flashcards
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How does bone repair?
produces new matrix, just like the previous matrix
Bone remodeling is ______, which allows it to respond to stresses.
continuous
Devitalized, demineralized bone contains:
growth and differentiation factors that will stimulate bone growth in ectopic sites (even under skin)
What cells deposit bone matrix?
osteoblasts
What is made in response to BMP?
Specific transcription factors for osteoblast differentiation
(BMP = developmental regulators)
How does bone respond to a demand for Ca?
Demand for calcium stimulates bone matrix resorption by osteoclasts, which releases Ca2+
Serves as Ca reservoir
bone
How are osteoclasts formed?
via differentiation and fusion of monocytes, which involves cell-cell interaction with osteoblasts through a RANK-RANKL interaction
How do osteoclasts act on bone matrix?
Release acid and protease into sealed off region of bone matrix below cell body, which allows for its reabsorption
Bone is constantly remodeled in response to:
- demands for calcium
2. mechanical stresses that demand enhanced or reduced bone mass
Hormone which enhances calcium release
parathyroid
Hormone which opposes the release of calcium
calcitonin
What are the functions of calcitriol and vitamin D3?
calcium absorption and bone mineralization
How does endochondral bone form?
- cartilage becomes calcified
- calcified cartilage then replaced by bone matrix and vasc bed at growing ends of bone
(Bone forms on a cartilage scaffold)
Components of cartilage (like type II collagen and aggrecan) are replaced by:
bone specific proteins:
- osteocalcin
- osteopontin
- bone sialoprotein
- highly crosslinked type I collagen
What is commonly used as a bone turnover measurement?
bone collagen crosslinks derived from HYL
Bone remodeling occurs via concerted action of:
osteoblasts and osteoclasts
Bone remodeling is regulated by what hormones?
PTH
calcitonin
active form of vitamin D
Bone forms from a _______ in development.
cartilage scaffold
Inbalance between formation and resorption can lead to:
bone disorders
Paget’s, osteoporosis, osteosclerosis, etc
Ca+ is excreted via:
sweat
urine
lactation
What is protective against osteoporosis?
Early buildup of bone mass in prepuberty and early adulthood
How do you treat Paget’s and osteoporosis?
bisphosphonates
Ca is stored in bone as:
HAP (hydroxyapatite, a hydroxyl calcium phosphate)
Bone is characterized by:
specific bone proteins and a collagen that is highly crosslinked
