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45 Cards in this Set

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List 5 organic compnents of the bone.

Describe each.
Osteoid - unmineralized bone

Osteoprogenitor cells - pluripotential mesenchymal stem cells; give rise to osteoblasts

Osteoblasts - matrix synthesis and transport arrangement

Osteocytes - controls Ca/Phosphorus level; detects mechanical forces and translate into biological activity


Osteoclasts - bone resorption
List the function and cell of origin of osteoblast.
From Osteoprogenitor cell

Function - matrix synthesis, transport arrangement
List the function and cell of origin of osteoclast.

List 3 stimulators and 1 inhibitor of osteoclast.
from hematopoietic progenitor cell

function - bone resorption

stimulators: cytokines, GFs, and RANK ligand.

Inhibitor: osteoprotegerin (OPG)
List the function and cell of origin of osteocyte.
Originate from osteoblast (trapped osteoblast in the canalicular network)

function - involved in mechanotransduction; translates mechanical forces into biological activity
What is mechanotransduction?
detect mechanical forces and translates into biological activity
What is Howship lacunae?
scallop resorption pits made by acidification, enzymatic digestion via osteoclasts
What is basic multicellular unit of the bone?

What cells are included in the unit?
functional unit of the bone involved in modeling (initial growth) and remodeling (skeletal maintenance).

osteocytes, osteoblasts, osteoclasts.
Compare and contrast woven bone vs lamellar bone.
Woven bone - random weave of bone
in fetal skeleton and growth plates
in diseased or repairing adult bone

lamellar bone - in orderly layers
normal bone of adult
stronger than woven bone
has cement lines
List 4 steps in bone development.
1. Condensation of primitive mesenchyme (homeobox genes)

2. Differentiation of chondrocytes and osteoblasts

3. Ossification (endochondral and intramembranous)

4. Enlargement: appositional growth.
What is the role of homeobox genes?
condensation of primitive mesenchyme during embryonic period.
Label this bone
A. Diaphysis
B. Metaphysis
C. Epiphysis
D. Growth plates
what is osteopenia?

What is osteoporosis?
Osteopenia - decreased bone mass

Osteoporosis - atrophy of bone tissue
Compare and contrast dysotoses from dysplasia
Dysotoses - localized problem; problem with migration of mesenchymal cells or formation of condensations

Dyplasia - abnormal organization of cells; affects skeletal tissue globally
What is craniorachischisis?

General etiology?
failure of closure of spinal column and skull.

Defects in nuclear proteins and transcription factors
Achondroplasia.


What is it?
Etiology/pathophysiology?
Results in?
Inheritance pattern?
Morphological changes?
Most common growth plate disorder

Defect in paracrine growth signaling --> reduced physial chondrocyte proliferation

results in dwarfism

Morphological changes: narrow plate with reduced proliferating cartilage; transverse bars of bone sealing off plate
Mucopolysaccridoses

Cause?
Results in?
Morphological changes?
Decreased degradation of MPSs (mucopolysaccharides) --> deposition in the physis

results in short stature and malformed bones

Morphological changes in the physis: widened plate with stored MPS in chondrocytes; transverse bars of bone sealing off plate
Osteogenesis imperfecta

Synonym?
Etiology?
morphology?
clinical presentations? (include extraosseous involvement)
Synonym: brittle bone disease

Etiology: mutations in genes for type I collagen (mainly AD)

Basic abnormality: osteopenia: extreme skeletal fragility

Extraosseous involvement:
a) Joints, skin, teeth
b) Eyes: “blue sclerae”
c) Ears: abnormal bone conduction
Osteopetrosis

Synonym?
Pathogenesis?
clinical presentations?
Synonym: marble bone disease

Pathogenesis: decrease osteoclast formation or function --> decreased bone resorption --> diffuse skeletal sclerosis (stonelike but brittle)

Clinical presentations: fractures, bony overgrowth ( can lead to anemia, infections, and CN compression), elongated metaphysis in femur (Erlenmeyrflask deformity)
What is the definition of osteoporosis?

List 3 primary etiologies of osteoporosis.

LIst a few secondary etiologies of osteoporosis.
Osteoporosis: atrophy of bone tissue; BMD ≥ 2.5 SDs below that of a normal young adult.

3 primary etologies
1. postmenopause
2. senile
3. idiopathic

secondary etilogies
1. exogenous corticosteroids
2. Endocrine disorders (e.g. Cushing's)
3. Chronic renal disease, neoplasia, GI disorders. etc.
Describe the pathogenesis behind postmenopausal osteoporosis.
Decreased serum estrogen --> increased IL-1,6 and TNF levels --> Increased RANK/RANKL and decreased OPG --> increased osteoclast activity
List 6 ways aging can cause osteoporosis.
1. decreased replicative activity of osteoprogenitor cells.
2. decreased synthetic activity of osteoblasts
3. decreased biologic activity of matrix-bound GFs.
4. reduced physical activity
5. decreased intestinal Ca absorption.
6. decreased renal synthesis of active form of Vit D.
List clinical manifestation of osteoporosis.
1. loss of height.
2. kyphoscoliosis
3. pulmonary complications
70 YO Caucasian male with pain in the proximal femur. Histology reveals mosaic pattern of lamellar bone.

What disease?
Osteitis deformans (Paget's disease)
List 3 phases of osteitis deforman.

Is there a net gain or loss of bone mass?
1. osteolytic phase
2. mixed osteoclastic-osteoblastic phase
3. ostoesclerotic phase

Net gain in bone mass
What is the pathogenesis of Paget's disease?
RANK signaling --> increased NF-kB activation --> increased
osteoclast recruitment, activity

Hyperresponsiveness of affected osteoclasts to: vitamin D and RANKL
List 2 main complications of Paget's disease.
Leontiasis ossea - enlarged facial bones, coarsening of features

Platybasia - invagination of base of skull, due to increased weight of skull
Causes in rickets in children and osteomalcia in adults.

Cause?
Pathogenesis?
Vitamin D deficiency.

Decreased bone Ca --> defective osteoid mineralization --> cartilage fails to calcify --> chondrocytes fail to mature and disintegrate
Causes scurvy.

cause?
Pathogenesis?
Vitamin C deficiency

↓ normally cross-linked collagen --> defective osteoid formation: normal woven bone is not formed; calcified cartilage resorbed by osteoclasts
Hypercalcemia, dissecitng osteitis, and brown tumor.

Cause? (primary or secondary?)

what is dissecting osteitis?
What is brown tumor?
Primary hyperPTH

Dissecting osteitis - osteoclasts tunnel into and dissect centrally along the length of trabeculae, creating the appearance of railroad tracks

Brown tumor - multicystic mass and hemosiderin deposition in the bone.
Describe the pathogenesis in renal osteodystrophy.
renal dysfunction --> phosphate retention and decreased vit D --> hypocalcemia --> secondary hyperPTH
What is von Recklinghausen disease of bone?
A complication of hyperPTH.

Symptoms: hemorrhage --> cystic degeneration
List 8 types of bone fracture.
1. complete and incomplete (greenstick)
2. closed (simple) and compound
3. comminuted
4. dispalced
5. pathologic
6. stress
What is bone callus? Procallus?
Bone callus - extra-ossification around the healing area.

Bone procallus - granulation tissue in the bone during the healing process.
Describe the process of bone repair.
1. Inflammation: granulation tissue ingrowth and release of GFs and interleukins (activate osteoprogenitor cells to differentiate into osteoblasts and chondrocytes)
2. Repair: callus formation
3. Remodeling: Woven bone --> lamellar bone
What is delayed union?

What factors can cause non-union?
Delayed union of the fractured bone occurs in fracture complications.

They can be caused by:
1. age (older)
2. Vascular insufficiency
3. malnutrition
4. misalignment.
5. excessive mobility.
What causes non-union of the bone in bone fracture?

What happens to the non-union bone?
Excessive mobility --> non-union

the bone forms:
1. nonssified fibrocartilagenous tissue
2. pseudoarthrosis: joint-like tissue with synoviocytes
3. infection might occur.
What is osteonecrosis?

Common predisposing factor?

Common locations?

Complication?
Osteonecrosis is ischemic necrosis of bone or marrow

predisposing factors: tenuous blood supply.

Commonly occurs in the femoral head. other sites include humeral head, distal femur, talus, carpal bones.

Complication: arthritis
What is Caisson's disease?
Thrombus/embolus in the vascular supply near femoral or humeral head causing osteonecrosis.
What is creeping substitution?
It is a process of osteoclasts resorbing the necrotic trabeculae during the healing process. However, those that remain act as scaffolding for the deposition of new bone.
What is osteomyelitis?

List 3 common organisms involved in osteomyelitis.

List 3 pathogenesis.
Osteomyelitis - inflammation of bone or marrow

3 organisms recovered
1. Staph aureus
2. Gram neg enterics
3. Salmonella

Pathogenesis
1. direct implantation
2. hematogenous spread
3. extension from contiguous site
What is Sequestrum?

How does this occur?
Sequestrum is necrotic bone embedded in pus.

process: suppuration --> pressure on vessels --> ischemia --> sequestrum
What is involucrum?
Reactive sheath of periosteal new bone around sequestrum in response to extracortical, subperiosteal dissection of pus
What is Brodie abscess?
bone abscess walled off by reactive bone; usually in the metaphysis
List 3 complications of osteomyelitis.
1. dissemination: septicemia, endocartidis.
2. septic arthritis
3. chronic osteomeylitis
What is Pott's disease?

Location?

Complications
A complication of TB (TB osteomyelitis)

Occurs in the spine, esp. T11

Complications
1. compression fracture --> kyphosis
2. neurological deficits
3. TB arthritis
4. REactive systemic amyloidosis