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phys: bone & gen med: ortho > Bone Phys > Flashcards

Bone Phys Flashcards

1
Q

An osteon is asst. with what type of bone?

A

Compact/cortical bone

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2
Q

Trabeculae are asst. with what type of bone?

A

Spongey/cancellous bone

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3
Q

What is the composition of bone?

A
  1. Mineral matrix of calcium and phosphate salts
  2. Collagen fibers and water
  3. Organic matter
  4. Inorganic matter
  5. Bony matrix
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4
Q

What is the organic matter of the bone?

A

Bone cells, collagen fibers, blood vessels and nerves

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5
Q

What is the inorganic matter of the bone?

A

Ca++ and PO4 salts –> Hydroxyapatite crystals

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6
Q

What is the bony matrix of the bone?

A

Dense cortical tissue w/ inner elastic trabecular tissue w/in marrow spaces

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7
Q

What is an osteoprogenitor cell?

A 
Osteoprogenitor cells (type of stem cell)
periosteum, endosteum and epiphyseal plates osteoblasts
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8
Q

What is an osteocyte?

A

mature bone cells maintaining bony matrix

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9
Q

What is an osteoblast?

A

bone-building cells

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10
Q

What is an osteoclast

A

bone-destroying cells (phagocytic lineage)

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11
Q

What are the functions of the bones?

A
  1. Provide rigidity, hardness, strength & support for body
  2. Protects vital internal organs
  3. Stores lead and other heavy metals*
    A. Released later for excretion
  4. Stores minerals calcium & phosphorus
    Role in calcium balance
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12
Q

Define tensile strength

A 
Tensile strength (collagen fibers)
strength to endure stretching forces
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13
Q

Define Compressional strength

A 
Compressional strength (calcium salts)
strength to endure squeezing forces
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14
Q

Define Bone remodeling

A
  1. Lifelong process
    A. Bone resorption and new bone formation (ossification)
    B. Micro-damage to bones during nl activity
  2. Following fractures
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15
Q

What are bone turnover markers?

A
  1. serum and urine
    A. Nl process of bone resorption results in release of bone mineral and osteoid (unmineralized bone, which is composed of collagen
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16
Q

Why is bone remodeling a dynamic process?

A

Bone resorption (osteoclasts) and bone formation (osteoblasts)

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17
Q

What is hyaline cartilage?

A
  1. Most abundant, 80% is H2O w/in gel structure

2. Articular cartilage

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18
Q

What is fibrocartilage?

A

Intervertebral disks, areas of tendons connected to bone, menisci

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19
Q

Where is a primary ossification center?

A

Diaphysis

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20
Q

Where is a secondary ossification center?

A

Epiphysis

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21
Q

Define diaphysis

A

Central area of the bone

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22
Q

Define epiphysis

A

Ends of the bone

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23
Q

What system regulates bone physiology?

A

Endocrine system maintains plasma and bone calcium and phosphate balance:

24
Q

What hormones are involved in maintaining bones?

A

Parathyroid hormone (PTH)*
Calcitriol (1,25- (OH)2 vitamin D3)**: most active metabolite of VD
Calcitonin

25
Q

How is estrogen related to bone density?

A

Estrogen supports normal bone metabolism by stimulating osteoblastic activity and limiting osteoclastic activity

26
Q

What is PTH secretion regulated by?

A

PTH secretion follows negative feedback regulation

 Ca++ stimulates PTH release

27
Q

Where is 99% of the body’s calcium located?

A

Bones

28
Q

How does the parathyroid gland maintain bone density?

A
  1. When serum Ca++ , PTH is secreted by chief cells of gland
    A. inc Bone Resorption
    stimulates osteoclast activity to release stored Ca++ ions and PO4
    B. Inc Intestinal absorption of Ca++ by enhancing the action of calcitriol
    C. inc Ca++ reabsorption and dec PO4 reabsorption @ kidneys
29
Q

How does the thyroid gland maintain bone density?

A
  1. When serum Ca++ inc, calcitonin is released from parafollicular (or C) cells of gland
  2. dec Bone Resorption (inhibits osteoclast activity)
  3. No effect on intestines
  4. inc excretion of Ca++
30
Q

Describe VD3

A

Cholecalciferol

31
Q

Describe VD2

A

Ergocalciferol

32
Q

True/faslse: vitamin D is not a vitamin

A

True: steroid hormone

33
Q

How much of calcium is active/free?

A

½ of circulating calcium is bound to albumin

Free, ionized calcium is physiologically active

34
Q

What are the sources of vitamin D?

A
  1. Skin production (d3) from UVB/A rays (90%)

2. jejunal absorption (D2 and D3) 10%

35
Q

What is the role of calcitonin?

A
  1. Calcitonin inhibits D3 production by the kidney

2. Inhibit bone resorption

36
Q

How is inactive D3 metabolized to active D3?

A

Inactive form D3 –> liver 25 (OH)D3 –> Kidneys –>1,25(OH)2D3

37
Q

What is the active form of Vitamin D3?

A

1,25(OH)2D3 = calcitriol

38
Q

What are the sxs of hypocalcemia?

A 
1. Paresthesias
A. Perioral, hands, feet
2. muscle cramps or spasms
3. bradycardia
4. lightheadedness
39
Q

What is Chvostek’s sign?

A

Tap over the facial nerve

Positive: twitch

40
Q

What is Trousseau’s sign?

A

Carpal pedal spasm when BP cuff is on and inflated above systolic bp

41
Q

What are the sxs of hypercalcemia?

A
  1. Kidney stones
  2. Bone pain, osteoporosis
  3. GI upset
    A. N/V
    B. PUD
  4. “thrones”- polyuria and constipation
  5. CNS effects
    A. Lethargy, fatigue, depression, psychosis, delirium, coma
42
Q

What is the Mnemonic: for hypercalcemia?

A

“Stones, bones, abdominal groans, thrones and psychiatric moans”

43
Q

What is the cause of hypercalcemia?

A

Cause of hypercalcemia is primary hyperparathyroidism caused by parathyroid adenoma

44
Q

Define osteopenia/osteoporosis

A
  1. Low bone mass/ Very low bone mass
  2. Osteoclast activity > osteoblast activity
    A. Weak bones
    B> inc risk of fractures
45
Q

When is peak bone mass?

A

Peak bone mass 25-29 yo, plateaus, then decreases perimenopausally (in men, age 60?)

46
Q

What can osteopenia/osteoporosis be caused by?

A

hyperparathyroidism

47
Q

Define osteomalacia

A
  1. “Softening of bones”

2. Weak and flexible bones d/t defective mineralization of bones

48
Q

What are the 2 main causes of osteomalacia?

A
  1. Insufficient Ca++ absorption from intestines d/t lack of dietary Ca++ or a deficiency of or resistance to vitamin D
  2. PO4 deficiency caused by inc renal losses or dec intestinal absorption
  3. Can result from kidney failure or hyperparathyroidism also
49
Q

What is metabolic rickets?

A

Metabolic bone disorder d/t defective mineralization of growing bones in children –> permanent bone deformities

50
Q

What is nutritional rickets?

A

inadequate exposure to sunlight and/or inadequate intake of vitamin D, calcium or phosphate

51
Q

What can nutritional rickets be caused by?

A
  1. Underdeveloped countries
  2. Prolonged breast-feeding w/o vit D supplementation
  3. Soy or rice beverages not fortified w/ vit D
52
Q

What are the physical signs of rickets?

A

Femurs bend laterally and affected person has bowlegged appearance (genu varum)

53
Q

What are the daily requirements of vitamin D?

A

Vitamin D3 800-1,000 IU Daily

54
Q

What are the calcium carbonate/citrate daily requirements?

A 
A. >50 yo 1,200 mg
B. 19-50 yo 1,000 mg
C. 9-13 yo 1,300 mg
D. 4-8 yo 800 mg
E. 1-3 yo 500 mg
Where can calcium carbonate be found? Tums
55
Q

Why does kidney failure lead to osteomalacia?

A

Inactive VD3 cannot be converted into active VD3, increased risk of fracture

56
Q

How much calcium can a person absorb at one time?

A

500-600 mg

phys: bone & gen med: ortho (14 decks)

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