Msk 1 & 2 Flashcards
What is the organic part of bone extracellular matrix called?
Osteoid - >90% type 1 collagen fibers 1.7
What is the mineral part of bone extracellular matrix called?
hydroxyapatitie - Ca10(PO4)6(OH)2 1.7
Which bone cell type senses mechanical stress?
Osteocytes 1.8
What is another name for “dense bone?”
Cortical bone 1.9
What happens in intramembranous ossification?
Bone develops from mesenchyme or fibrous conective tissue: flat bones of skull, mandible, clavicles 1.13
What happens in endochondral ossification?
Bone replaces existing cartilage; bone grows on epiphyseal plate (epiphyseal growth) 1.12, 1.16
What differentiates calcification from ossification?
Calcification is mineralization of bone. Ossification is formation of bone.
How does epiphysesal closure occur during puberty/teenage years?
Sex homones increase bone formation rate. Rate is faster than cartilage formation. Inhibition of osteoclasts. Plate becomes line. 1.16
What is another name for “bones growing thicker?”
Appositional growth 1.16
PTH stimulates osteoblasts to release what molecules?
IL-6 & RANK Ligand promote maturation and activation of osteoclasts 1.20
Do osteoclasts have PTH receptors?
No. They are stimulated by IL-6 & RANK Ligand Ibinds to RANK) 1.20
What is the purpose of a ruffled osteoclast membrane?
Increases surface area for maximal bone contact 1.20
What does RANK stand for?
Receptor for Activation of Nuclear factor kappa B (NF-KB)
Which protein limits osteoclast activity?
Osteoprotegerin (OPG) produced by osteoblasts and stromal cells 1.21
What does OPG do?
Binds RANK ligand and blocks RANK interaction to limit osteoclast activity 1.21
Genetic defects of _____ and/or _____ cause bone disorders.
RANK Ligand, OPG expression 1.21
Which enzyme is important for normal osteoclast activity?
Carbonic anhydrase (CA) - provides H+ 1.23
How do osteoclasts seal themselves to bone?
Integrin-vitronectin interaction (vitronectin on bone) 1.23
What is the most common cause of osteoporosis in post-menopausal women?
Estrogen deficiency
What are the criteria for bone mineral density of normal, osteopenia, and osteoporosis?
Above -1.0 SD
Btwn -1.0 and -2.5 SD
Below -2.5 SD
Group of genetic diseases - reduced bone resorption due to low osteoclast activity, skeletal scerosis (stonelike quality), abnormally brittle bones
Osteopetrosis
Erlenmeyer flask deformity seen on xray - distal metaphyses of ulna & radius are poorly formed
Osteopetrosis
Poor bone mineralization, Vit D & P/Ca deficiencies in adults
Osteomalacia
Vit D & P/Ca deficiencies in childhood, poor mineralization, bowing of legs
Rickets
