12. USMLE MSK I
Terms in this set (66)
in which type of bone growth does the cartilage model get put down before the woven bone? what cells secrete the collagen?
endochondral ossification; chondrocytes
what bones use endochondral ossification?
long bones, vertebrae, pelvis, bones of base of skull
in what type of bone formation is woven bone formed directly without cartilage?what bones use this bone formation?
membranous ossification; vault of skull, maxilla, mandible
what is the source of osteblasts?
mesenchymal stem cells in periosteum
what hormones are involved in growth?
GH, thyroid hormone, sex hormones
what is the name of the diseases that results in a failure of longitidunal bone growth, but has normal membranous ossification ? what causes the defect?
achondroplasia; constitutive activation of FGFR3 (fibroblast growth factor receptor 3) which actually inhibits chondrocyte proliferation
T/F majority of achondroplasia are from the AD form
false- from the sporadic form (though a hereditary AD form does exist)
what disease is associated with advanced paternal age?
what is the difference between the woven bone and the lamellar bone formed in both membranous and endochondral ossificiation? when is woven bone formed?
woven is immature and randomly arranged collagen in osteoid; lamellar is regular parallel bands of collagen sheets; woven bone formed in fetal bone development and with pathologic rapid new bone formation
name two conditions in adulthood when you see woven bone.
healthy fracture and Pagets disease
what is the fate of all woven bone?
to form stronger more resilient lamellar bone
what is the composition of bone?
70% inorganic salts (minerals) and 30% organic matrix -- the inorganic salts are what provide the rigidity of bone
is the 70% of inorganic matrix of bone crystallized or non crystallized minerals? explain.
both- mainly crystallized; bone is formed by deposition of amorphous calcium phosphate salts (noncrystalline) into holes of collagen- the noncrystalline salts then coalesce to form hydroxyapatite crystals-- 20% of the inorganic matrix is in noncrystalline calcium phospate matrix to provide ready buffer in whole body calcium homeostasis
what provides the balance between crystalline and noncrystalline salts? which one provides the bone rigiditY ? ready buffer for calcium homeostasis? what are the crystals called?
pyrophosphates (anticrystallization) and alkaline phosphatases (procrystallization); crystals; noncrystalline form; hydroxyapatite crystals
what exactly is "bone"? what part provides the rigidity and strength?
cells, predominantly collagen ECM (type 1 collagen) called osteoid which is secreted by osteoblasts which becomes mineralized by deposition of calcium hydroxyapatite crystals; the crystals!
what cells secrete osteoid? what is osteoid? what are the precursors to these cells? where are osteoblasts found?
osteblasts; collagenous ECM (type 1 collagen); mesenchymal stem cells; lined up along bone surfaces
what is the difference between osteoblasts and osteocytes? what are the precursors to osteocytes? where are osteocytes found?
largely inactive osteoblasts (is what osteocytes are- not precursor, but inactive!); mesenchymal stem cells; trapped in formed bone
which cells initiate resorption of bone? what is their precursor? what is the signal to begin resorption?
osteoclasts (phagocytic cells!); macrophage-monocyte line!; growth, changing mechanical stresses, PTH, calcitonin
going out to in, name the four layers of bone.
1) dense rigid outer shell of bone is called compact bone
3)central medullary/cancellous bone made up of thin interconnecting bone trabecullae
4) spaces in b/w trabecullae in medullary bone is occupied by hematopoietic bone marrow
what are the two types of lamellar bone? where is each found?
compact bone forms the dense walls seen in the diaphysis (long middle part); cancellous/medullary bone found in medullary center of bone (trabecular bone)
what are the epiphyses? what protects them?
articular/joint surfaces of expanded ends; articular cartilage
where do tendons, muscles, ligaments attach on bones? what else happens in this layer? what is it made of?
periosteum (most outer layer of bone); where mesenchymal precursor stem cells are for osteoblasts; fibrinous layer
where in the bone (macro-size) does endochondrous ossification occur?
the junction between epiphysis and diaphysis- metaphysis
what part of the bone does osteomyelitis usually affect?
what dictates the number and thickness of trabecular bone?
the stresses to which that particular bone is exposed (thick and a lot in weight bearing bones, but ribs have thin few trabeculae)
where can you find the haversian system? what is it?
in compact (cortical) bone; parallel bony columns found in outside of bone with each column made up of concentric layers of lamellae/osteoid organized around central channel of haversian canal
is there a haversian system in trabecular bone?
what makes up an osteon?
the column of concentric lamellar osteoid surrounding a central haversian canal
where are osteocytes found specifically? what are lacunae?
in lacunae in the osteons; becuase the concentric circles are made by osteoblasts secreting osteoid from the inside to the outside of the osteon, the osteoblasts that make each layer get stuck in that layer in these little spaces called lacunae and become osteocytes
what are the volkmanns canals? cannaliculi?
volkmann canals pierce the columns of osteoid/lamella in an osteon at right angles and come off of the haversian canal vessels; connect lacunae to the central haversian canal
what are found in the haversian canals?
blood vessels, nerves, lymphatics
where do the blood vessels found in haversian canals found?
they come from the medullary/trabeculae bone marrow space- they penetrate into the cortical bone via the endosteum
what is the endosteum? what do they contain?
the most inner layer of the cortical bone- the layer between the cortical and trabecular bone' contain inactive osteoblasts that when activated (by stress for example) start laying down new concentric lamellae and create osteons- woven and unorganized at first of course
what do the osteocytes in the lacunae do?
maintain the integrity of the mineral matrix of the bone and mediate release of the noncrystalline calcium and deposition etc
osteoporosis is a reduction in what type of bone? what are the two primary types of osteoporosis?
trabecular (spongy) bone; type 1- postmenopausal d/t decreased estrogen levels (results in decreased osteoblastic and increased osteoclastic activities) and type II- senile osteporosis- affects women and men over than 70 y/p
what are the lab values in osteoporosis?
what causes secondary osteoporosis? name 5 causes.
hypercorticolism; heparin (and other drugs); hypoPtH; lack of gravity; malnutrition (AN)
what are three fractures seen commonly in osteporosis?
vertebral crush fractures (lack of trabeculae- crush!); femoral neck fractures; distal radius fractures
what is a Colles' fracture?
distal radius fractures in osteoporosis
how do vertebral crush fractures present? what are they seen in ?
acute back pain, loss of height, kyphosis; osteoporosis
what is the prophylaxis for osteoporosis? treatment?
weight bearing exercises and calcium ingestion before the age of 30; estrogen (SERMs) and/or calcitonin; biphosphonates or pulsatile PTH for severe cases
what is contraindicated in osteoprosis?
what disease is characterized by failure of normal bone resorption? what are the lab values? what is the disease also known as?
osteopetrosis; normal; marble bone disease
in osteopetrosis what causes patients to be prone to fractures?
thickened, dense bones that are prone to fracture d/t abnormal osteclastic activity
what is the actual deficiency that causes decreased osteoclastic activity in osteopetrosis? what do x rays show?
carbonic anhydrase deficiency; erlenmeyer flask bones that flare out
what are the non bone related symptoms that osteopetrosis presents with? whY?
visual and hearing loss-- cranial nerve impingement d/t narrowed foramina
what effect does thickened dense bones in osteopetrosis have on the rest of the bone components? how does this present?
anemia, thrombocytopenia, infection (the way that aplastic anemia presents); increased EMH
what does Vit D def cause in children? adults?
what does vit D def in rickets and osteomalacia cause?
deficient mineralization of osteoid; can be caused by lack of phosphate also! (kidney failure- more rare)
T/F osteomalacia is not reversibel
what is Pagets disease also known as? what is the common population it presents in? what is thought to cause it?
osteitis deformans; older men; paramyxo virus
what causes the mosaic bone pattern seen in osteitis deformans? what are the serum values?
increase in both osteoblastic (woven bone!) and osteoclastic activity; all normal except for increased ALP (d/t osteoblastic activity following osteoclastic activity)
what is the clinical manifestation of osteitis deformans? (think bone and non bone- hat, hear, high)
long bone chalk stick fractures (woven bone is not stable!); increased hat size; hearing loss (auditory foramen narrowing); high output failure (increased bone formation causes arteriovenous malformations)
which bone disease causes an increase in hat size? which cause hearing or vision loss?
pagets; pagets and osteopetrosis
what is the treatment for pagets?
biphosphonates and calcitonin
what does hyperPTH cause in bones?
"brown" tumors- radiologically lucent; hypercalciuria
what are the lab values in osteoporosis? osteopetrosis?
no change; no change
what are the lab values in osteomalacia/rickets?
PTH up, calcium down, phosphate down, ALP normal
what are the lab values in osteitis fibrosa cystica? what is that?
calcium high, PTH high, phosphate low, ALP high; "brown tumors" seen in hyperparathyroidism!
what are the lab values seen in pagets disease?
normal everything except increased ALP
what is the ALP level in osteitis fibrosa cystica? pagets? everything else?
high; high; normal
what are the lab values seen in hypervitaminosis D (Sarcoid for ex)?
PTH down, Ca high, phosphate high, normal ALP, high vit D (DUH!)
what are the lab values seen in renal insufficiency?
high phosphate, low Ca, increased PTH, normal ALP
what is polyostotic fibrous dysplasia? what can cause it?
it is when medullary bone is replaced by fibroblasts, collagen, and irregular bony trabeculae with cyst formation; McCune-Albright syndrome
other than mulitple unilateral bone lesions what else is McCune Albright syndrome associated with?
endocrine abnormalities (precocious puberty) and unilateral pigmented skin lesions (cafe au lait spots/Coast of Maine spots )
what are the complications of polyostotic fibrous dysplasia? how does it present?
osteogenic sarcoma, fracture, fibrosarcoma; bone pain
(mostly in ribs)
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