Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
68 Cards in this Set
- Front
- Back
|
2 Ways that bone develops:
|
1. Intramembranous
2. Endochondral |
|
|
What forms from intramembranous ossification?
|
Flat bones
|
|
|
What forms from endochondral ossification?
|
Long bones
|
|
|
How does Intramembranous ossification proceed in general?
|
Bone forms in ossification centers.
|
|
|
What begins the ossification center development?
|
Mesenchyme condensation
|
|
|
What does that ossification center allow?
|
Osteoblasts can secrete osteoid onto it.
|
|
|
What happens to the osteoid that osteoblasts secrete onto the ossification center?
|
It calcifies and incorporates osteocytes into individual lacunae.
|
|
|
What bone forming is an example of intramembranous ossification?
|
Filling in the fontanelles of the calvarium in neonates.
|
|
|
How does Endochondral ossification proceed in general?
|
Osteoblasts deposit osteoid onto an already existing template of hyaline cartilage.
|
|
|
What is the first step in Endochondral ossification?
|
Deposition of a bone collar around the perichondrium of the hyaline cartilage template; forms the future diaphysis.
|
|
|
What happens after forming the bone collar?
|
The cartilage cells that got surrounded by osteoid hypertrophy and apoptose.
|
|
|
What finishes forming of the diaphysis?
|
Osteoblasts secrete more bone on the matrix of calcified cartilage; the marrow cavity gets cavitated.
|
|
|
How do the epiphyses form in long bones?
|
Via the same endochondral ossification that forms the diaphysis. However some hyaline cartilage is retained.
|
|
|
What are the 2 forms in which hyaline cartilage is retained at the epiphysis during endochondral ossification?
|
1. Epiphyseal plate cartilage
2. Articular cartilage |
|
|
Why is epiphyseal plate cartilage retained?
|
So that these long bones can grow in length.
|
|
|
What is the first step in long bones growth lengthwise?
|
Activation of hyaline epiphyseal cartilages (retained at the epiphyses).
|
|
|
How long do humans retain their hyaline epiphyseal plates?
|
Until age 20
|
|
|
What also occurs as bones grow in length?
|
Widening
|
|
|
What 5 zones are recognized during long bone growth in length?
|
1. Reserve zone
2. Proliferative zone 3. Zone of hypertrophy 4. Zone of calcification 5. Ossification |
|
|
What is in the Reserve Zone?
|
Cartilage - maintained as a backup store.
|
|
|
What hormone induces cartilage to form in the reserve zone?
|
Somatotropin - growth hormone.
|
|
|
What induces the pituitary to express this somatotropin/GH?
|
Sex steroids - estrogen and testosterone.
|
|
|
What sustains the activity in the PROLIFERATIVE zone?
|
Somatomedins - Insulin like growth factor
|
|
|
What happens in the Hypertrophy zone?
|
20% of fractures in children
|
|
|
What type of collagen is in the CALCIFICATION zone?
|
Type X
|
|
|
What 2 cellular processes occur in the calcification zone?
|
-Chondrocyte proliferation is inhibited
-Hydroxyapatite formation begins |
|
|
What feature of the calcification zone makes it easier to identify?
|
Strong Basophilia
|
|
|
How is ossification initiated in the ossification zone?
|
By the invasion of OSTEOBLASTS.
|
|
|
What type of collagen do osteoblasts synthesize?
|
Type I collagen
|
|
|
What color develops due to the collagen type I deposition?
|
Eosinophilia
|
|
|
What 3 cells are involved in REPAIRING bone, and in what order?
|
1. Macrophages
2. Chondroblasts 3. osteoblasts |
|
|
What type of ossification occurs during bone repair?
|
Both intramembranous and endochondral.
|
|
|
What do Macrophages do during repair?
|
Remove clots
|
|
|
What do chondroblasts do?
|
Secrete a CALLUS of hyaline cartilage.
|
|
|
What do the osteoblasts do?
|
Replace the Cartilaginous callus with a Bony callus.
|
|
|
What has to take place after the bony callus is formed?
|
Remodeling - to replace the primary bone with secondary.
|
|
|
What do difficult fractures require for complete healing?
|
Bone Grafts
|
|
|
What is better for bone repair than bone grafts?
|
Inducing the normal bone repair process
|
|
|
What are 3 approaches to inducing bone repair normally?
|
1. Implants of BMP7 and BMP2
2. Implants of plasmids 3. Implants of mesenchymal stem cells |
|
|
What is necessary for implanting / injecting these agents?
|
Putting it in a natural matrix of collagen type i or plastic polymer.
|
|
|
How often is a new skeleton made?
|
Every 10 years
|
|
|
What 2 processes occur during bone remodeling?
|
1. Osteoclasts excavate bone
2. Osteoblasts replace it |
|
|
What hormone made by fat cells induces the CNS to inhibit bone formation?
|
Leptin
|
|
|
What is osteopetrosis and what causes it?
|
Too much dense heavy bone because osteoclasts lack a ruffled border.
|
|
|
What is osteoporosis?
|
Too much resorption of bone by osteoclsts
|
|
|
What score on a bone mineral densitometry indicates that a subject is at high risk for osteoporosis?
|
2.5 SD below the mean
|
|
|
What do osteoclasts differentiate from?
|
Stromal cells
|
|
|
What are stromal cells?
|
Osteoblasts that are like macrophages.
|
|
|
What induces stromal cells to secrete secretory products?
|
PTH
|
|
|
What products do osteoblasts intended to become osteoclasts secrete? How does each product affect the differentiation?
|
1. Rank-L - promotes osteoclast
2. M-CSF - promotes osteoclast 3. OPG - inhibits osteoclast |
|
|
What does M-CSF do?
|
Stimulates proliferation of macrophages
|
|
|
What does RANK-L do?
|
Induces the macrophages that proliferated to differentiate into osteoclasts.
|
|
|
How does OPG (osteoprotegerin) inhibit macrophage differntiation into osteoclasts?
|
By binding up the RANK-L receptor and preventing it from being bound by RANK-L.
|
|
|
What receptor adheres osteoclasts to bone matrix?
|
Integrin alpha5-beta3
|
|
|
Why is it good to know all about osteoclasts?
|
To treat osteoporosis.
|
|
|
Regarding Osteoblasts:
-What inhibits their forming? -What induces their forming? |
Leptin Inhibits osteoblasts
BMP/PTH induce osteoblasts |
|
|
Regarding Osteoclasts:
-What inhibits their forming? -What induces their forming? |
Calcitonin/OPG inhibit osteoclasts
RANK-L/PTH induce osteoclasts. |
|
|
How can PTH induce both osteoblasts and osteoclasts?
|
B/c its action is determined by HOW IT is released.
|
|
|
What type of PTH release stimulates osteoblasts?
|
Spikes
|
|
|
What type of PTH release stimulates osteoclasts?
|
Constant
|
|
|
What are 4 important anti-resorptive (antiosteoclast) drugs?
|
1. Estrogen/testosterone
2. SERMS 3. Bisphosphonates 4. Calcitonin |
|
|
How does estrogen work?
|
By inducing osteoclast apoptosis
|
|
|
What are 2 SERMs?
|
-Reloxifen
-Tamoxifen |
|
|
What is a major Pro-osteoblast drug?
|
PTH 1-34 INJECTED IN SPIKES
|
|
|
What is the necessary requirement for anti-resorptive drugs to work?
|
T-score must not be 2.5 SD below the mean.
|
|
|
What would a Cbfa-1 drug do?
|
Induce osteoblasts
|
|
|
What would inhibit osteoclasts binding the matrix?
|
Inhibiting Integrin alpha5-beta3
|
|
|
What would inhibit osteoclasts differentiation?
|
Osteoprotegerin
|
