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MSK/Derm > SM_233a: Metabolic Disease > Flashcards

SM_233a: Metabolic Disease Flashcards

1
Q

Describe the normal skeletal system

A

Normal skeletal system

  • 60-70% is inorganic matrix (calcium hydroxyapatite)
  • 30% is composed of organic elements (90% collagen type I) including osteocalcin (most abundant noncollagen protein/important for bone mineralization and acts as serum marker of bone formation and density)
  • Numerous growth factors including osteoblast-activating Transforming Growth Factor beta (TGF-beta) and bone morphogenic protein (BMP)
  • Cellular components: osteoblasts, osteocytes, and osteoclasts
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2
Q

Outside of bone is made of _____ bone while inside is made of _____

A

Outside of bone is made of cortical/lamellar bone while inside is made of spongy/trabecular/cancellous bone

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3
Q

Describe intramembranous bone formation

A

Intramembranous bone formation

  • Develops from collagen (collagen modeled bone)
  • Forms flat bones of skull and clavicles
  • Periosteal osteoprogenitor cells form osteoblasts and responsible for prepubertal thickening of cortex and bone widening (appositional bone growth)
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4
Q

Describe enchondral bone formation

A

Enchondral bone formation

  • Develops from epiphyseal cartilage of the growth plate (cartilage modeled bone)
  • Forms appendicular and axial skeleton and responsible for prepubertal bone lengthening
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5
Q

Enchondral bone formation is responsible for development of _____ skeleton

A

Enchondral bone formation is responsible for development of appendicular skeleton

(perturbations/arrest in normal endochondral ossification lead to many congenital and metabolic bone diseases)

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6
Q

____, ____, ____, and ____ stimulate cartilage growth in the zone of proliferation in enchondral bone formation

A

IHH, PTHrP, BMP, and ILGF-1 stimulate cartilage growth in the zone of proliferation in enchondral bone formation

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7
Q

____ inhibits cartilage growth in the zone of proliferation during enchondral bone formation

A

FGF inhibits cartilage growth in the zone of proliferation during enchondral bone formation

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8
Q

_____ and _____ are immature bone

A

Osteoid and woven bone are immature bone

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9
Q

____ is mature bone

A

Lamellar bone is mature bone

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10
Q

Osteoid is ______

A

Osteoid is unmineralized poorly organized bone matrix (Type I collagen) formed rapidly

(immature, becomes adult bone once mineralized)

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11
Q

Woven bone is _____

A

Woven bone is mineralized immature bone formed rapidly and the main component of prepubertal bone

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12
Q

Mineralized mature bone forms ____ and has ____ parallel ____ fibers and evenly distributed ____

A

Mineralized mature bone forms slowly and has parallel collagen type I fibers (lamellae) and evenly distributed osteocytes

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13
Q

Cortical (compact bone) involves _____, _____, and _____

A

Cortical (compact bone) involves collagen first deposited in circumferential lamellae, dissipation of mechanical stress via osteon formation, and collagen deposition around Haversian canals as concentric lamellae

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14
Q

Cancellous (spongy) bone is formed by ____ and involves deposition of ____

A

Cancellous (spongy) bone is formed by enchondral ossification and involves deposition of collagen in longitudinal lamellae

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15
Q

Cellular elements of bone are ____, ____, and ____

A

Cellular elements of bone are osteoblasts, osteocytes, and osteoclasts

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16
Q

Describe osteoblasts

A

Osteoblasts

  • Derived from mesenchymal stem cells & line surface of bone
  • Cell surface receptors include PTH, Vitamin D, estrogen, and others
  • Produce matrix proteins and type I collagen and initiate mineralization
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17
Q

Describe osteocytes

A

Osteocytes

  • Osteoblasts that are incorporated into mature bone (most common cells in bone)
  • Produce sclerostin: protein that inhibits further bone formation until osteocytes are stimulated
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18
Q

Describe osteoclasts

A

Osteoclasts

  • Multinucleated giant cells formed from monocytic progenitor cells in response to RANK-ligand secreted from osteoblasts and bone stromal cells
  • Responsible for bone resorption
  • Located in resorption pits / Howship’s lacunae
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19
Q

Osteoblasts contain ____, while osteoclast precursors contain ____

A

Osteoblasts contain RANK-L, while osteoclast precursors contain RANK

(binding together activates osteoclast so it can reabsorb bone)

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20
Q

Binding of RANK-L from osteoblasts to RANK on osteoclast precursors ____

A

Binding of RANK-L from osteoblasts to RANK on osteoclast precursors activates osteoclasts so they can reabsorb bone

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21
Q

Describe the osteoclast resorption pit

A

Osteoclast resorption pit

  • Forms a sealed acidified microenvironment in the resorption pits on the surface of bone
  • Ruffled membrane contains H+ ATPase (mutations in H+ ATPase are most common cause of osteopetrosis)
  • HCl mobilizes the mineral phase and proteinase cathepsin K degrades the organic matrix (type I collagen) -> releases minerals and growth factors from bone
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22
Q

Mutations in the ____ in the osteoclast resorption pit are the most common cause of osteopetrosis

A

Mutations in the H+ ATPase in the osteoclast resorption pit are the most common cause of osteopetrosis

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23
Q

Balanced interaction between ____ and ____ ensures normal bone structure through appropriate ____ in response to mechanical stress

A

Balanced interaction between osteclasts and osteblasts ensures normal bone structure through appropriate bone remodeling in response to mechanical stress

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24
Q

Bone remodeling is ____

A

Bone remodeling is a continuous process that dissipates bone stress throughout the life of the individual

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25
Q

Bone remodeling in cortical bone involves ____

A

Bone remodeling in cortical bone involves Haversian system with osteon formation

26
Q

Bone remodeling in cancellous bone involves ____

A

Bone remodeling in cancellous bone involves activation of osteoclasts and resorption of bone in Howship’s lacuna, then reversal of cell type (osteoblasts replace osteoclasts) leading to bone formation

27
Q

Describe osteon formation in cortical bone

A

Osteon formation in cortical bone

  • Osteons created in response to stress: aggregates of osteclasts form “cutting cones” and resorb bone (primary osteon) -> osteoblasts fill cavity with bone deposited in concentric lamellae
  • Osteocytes within rings of the osteon communicate through dendritic processes and regulate bone remodeling and mineral stores
28
Q

Describe bone remodeling in trabecular bone

A

Bone remodeling in trabecular bone

  1. Activation of osteoclasts
  2. Resorption of bone in Howship’s lacuna
  3. Reversal of cell type to osteoblasts
  4. Bone formation
29
Q

Describe acute osteomyelitis

A

Acute osteomyelitis

  • Caused mainly by bacterial infection resulting from hematogenous spread, contiguous spread from abscess or ulcer, direct inoculation of organism into bone, and ischemia (vascular insufficiency)
  • Staphylococcus aureus is most common infectious agent
  • Microscopically acute inflammatory cells are initimately associated with non-viable bone
  • Periosteum/endosteum responds by forming new bone (involucrum, star top) around dead infected bone
  • Managed by surgery and long course antibiotic therapy
30
Q

Categories of bone diseases include ____, ____, ____, ____, and ____

A

Categories of bone diseases include abnormal matrix, too little matrix, too little mineralization, too much bone resorption, and too little bone resorption

31
Q

Osteogenesis imperfecta involves an _____ matrix

A

Osteogenesis imperfecta involves an abnormal matrix

32
Q

Describe osteogenesis imperfecta

A

Osteogenesis imperfecta

  • Defect in synthesis of Type I collagen: abnormal Type I collagen results in more serious disease than decreased synthesis of collagen
  • Excess callus formation after fractures
  • Blue sclera
33
Q

Osteogenesis imperfecta involves a defect in synthesis of _____, excess _____ formation after fractures, and _____

A

Osteogenesis imperfecta involves a defect in synthesis of Type I collagen, excess callus formation after fractures, and blue sclera

34
Q

Osteoporosis has ____ matrix

A

Osteoporosis has too little matrix

35
Q

Describe osteoporosis

A

Osteoporosis

  • Bone that is histologically normal but decreased in quantity
  • ≥ 1 atraumatic fractures or low bone mineral density on DEXA
  • Can be localized: immobility, Sudeck’s atrophy, inflammatory focus around bone such as in rheumatoid arthritis
  • Generalized: senila and post menopausal osteoporosis
36
Q

Describe the pathogenesis of senile and postmenopausal osteoporosis

A

Senile and postmenopausal osteoporosis pathogenesis

  • Depends upon initial bone density and subsequent loss of bone that occurs wirth age
  • Bone mass peaks in early adulthood
  • With aging, osteblasts lose ability to form new bone and growth factors lose potency
  • Bone loss accentuated by activation of osteoclasts
37
Q

Describe postmenopausal osteoporosis

A

Postmenopausal osteoporosis

  • Estrogen deficiency upregulates osteoclastogenic factors and decreases OPG resulting in osteoclastogenesis
  • Affects bones with large surface area - fracture of vertebra and wrist
  • High-turnover: activity of osteoclasts > osteoblasts
38
Q

Describe senile osteoporosis

A

Senile osteoporosis

  • Men and women > 70 years of age
  • Caused by osteoblasts having decreased reproductive/biosynthetic potential with age and growth factors in matrix losing potency
  • Fractures involve hip and vertebra
  • Low-turnover: activity of osteoblasts low, normally active osteoclasts
39
Q

Postmenopausal osteoporosis is _____-turnover, while senile osteoporosis is _____-turnover

A

Postmenopausal osteoporosis is high-turnover, while senile osteoporosis is low-turnover

  • High-turnover osteoporosis: activity of osteoclasts > osteoblasts (which are active)
  • Low-turnover osteoporosis: activity of osteoblasts low, normally active osteoclasts
40
Q

Mucopolysaccharidoses are caused by mutations in ____, resulting in ____ and ____

A

Mucopolysaccharidoses are caused by mutations in lysosomal enzymes that degrade glycosaminoglycans, resulting in their accumulation and cellular damage

41
Q

Describe clinical signs and symptoms of mucopolysaccharidoses

A

Clinical signs and symptoms of mucopolysaccharidoses

  • Vary according to enzyme defect
  • Include cardiac valvular disease, mental retardation, hepatosplenomegaly, corneal clouding, umbilical/inguinal hernai, coarse facies, macroglossia, and enlarged gingiva
42
Q

Describe changes in bone and soft tissue in mucopolysaccharidoses

A

Changes in bone and soft tissue in mucopolysaccharidoses

  • Fibroblasts (tendons/ligaments), chondrocytes, osteoblasts, and osteoclasts
  • Defects in enchondral ossification lead to short stature, kyphosis/scoliosis, odontoid hypoplasia with risk of spinal cord compression and hypoplastic teeth
  • Abnormal intramembranous ossification leads to macrocephaly
  • Abnormal bone remodeling and enchondral ossification result in osteoporosis
  • Accumulation of GAG in tendons/ligaments of joints induces inflammation resulting in periarticular fibrosis, joint stiffness and/or hypermobility, and later secondary osteoarthritis
43
Q

Vitamin D deficiency (rickets/osteomalacia) involves ____

A

Vitamin D deficiency (rickets/osteomalacia) involves too little mineralization

44
Q

Describe Vitamin D deficiency (rickets / osteomalacia)

A

Vitamin D deficiency (rickets / osteomalacia)

  • Lack of calcification of growth plate (rickets) or of osteoid to form new adult bone (osteomalacia)
  • Increased PTH and decreased serum phosphate stimulate Vitamin D synthesis -> negative feedback
45
Q

Metaphyseal flare is indicative of _____

A

Metaphyseal flare is indicative of rickets

  • Vitamin D deficiency in children -> growth plate widens with cartilage
46
Q

Radiographs of rickets show _____, _____, and _____

A

Radiographs of rickets show femoral bowing, metaphyseal flaring, and rosary rickets (enlarged costochondral junctions in rib cage)

47
Q

Describe osteomalacia

A

Osteomalacia

  • Inability to calcify osteoid to form new adult bone during remodeling
  • Usually due to chronic renal failure
  • Results in insufficiency fractures on X-ray and bone pain
48
Q

Osteomalacic bone shows _____

A

Osteomalacic bone shows excess osteoid

49
Q

Hyperparathyroidism involves ____

A

Hyperparathyroidism involves too much bone resorption

50
Q

Clinically hyperparathyroidism involves ____, ____, ____, and ____

A

Clinically hyperparathyroidism involves (GI tract) moans, bones, (renal) stones, and psychiatric overtoens

51
Q

Hyperparathyroidism pathogenesis includes ____ and ____, resulting in ____

A

Hyperparathyroidism pathogenesis includes primary HPT (parathyroid adenoma followed by chief cell hyperplasia) and secondary HPT (parathyroid hyperplasia due to chronic renal failure), resulting in osteoclastogenesis and osteoporosis

(affects cortical > cancellous bone - bone loss in fingers and clavicles on X-ray)

52
Q

Hyperparathyroidism involves bone loss in ____ and ____ on X-ray

A

Hyperparathyroidism involves bone loss in fingers and clavicles on X-ray

(subperiosteal resorption)

53
Q
A
54
Q

In hyperparathyroidism, activated osteoclasts form ____ that reabsorb bone and there is ___ and also ___

A

In hyperparathyroidism, activated osteoclasts form “cutting cones” and there is dissecting osteitis (railroad track appearance of bony trabeculi due to central reabsorption of osteoclasts) and also subperiosteal cortical bone resorption by osteoclasts

55
Q

Features of hyperparathyroidism are ____ and ____

A

Features of hyperparathyroidism are dissecting osteitis and brown tumor of bone (osteitis fibrosa cystica)

  • Dissecting osteitis: aggreates of activated osteoclasts form a cutting cone along the longitudinal axis of a trabecula
  • Brown tumor of bone (osteitis fibrosa cystica): spindled stromal cells, osteoclasts, foci of hemorrhage, and hemosiderin deposits
56
Q

Paget’s disease involves _____ bone resorption

A

Paget’s disease involves too much bone resorption

57
Q

Paget’s disease is defined as ____

A

Paget’s disease is defined as collage of matrix madness due to dyssynchrony of osteoclastic/osteoblastic activity

58
Q

Paget’s disease pathogenesis involves ____

A

Paget’s disease pathogenesis involves upregulation of NF-kappaB osteoclastogenesis

59
Q

Paget’s disease manifests as _____ on X-ray

A

Paget’s disease manifests as characteristic tapering lytic process in distal femur

(osteolytic phase w/ enlarged oseoclasts, then osteosclerotic phase with thickened bone with a haphazard pattern of cement lines)

60
Q

Osteopetrosis involves ____ bone resorption

A

Osteopetrosis involves too little bone resorption

61
Q

Osteopetrosis involves ____ osteoclast activity, resulting in _____ bone

A

Osteopetrosis involves absent/defective osteoclast activity, resulting in abnormally thickened bone

(often osteoclasts fail to acidify resorption pits)

62
Q

Osteopetrosis manifests as _____ on X-ray

A

Osteopetrosis manifests as sclerotic medullary cavity on X-ray

(bones lack medullary canal)

(medullary hematopoietic bone marrow replaced by calcified cartilage and new bone)

MSK/Derm (49 decks)

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