Bone Phys

Question 1

An osteon is asst. with what type of bone?

Answer 1

Compact/cortical bone

Question 2

Trabeculae are asst. with what type of bone?

Answer 2

Spongey/cancellous bone

Question 3

What is the composition of bone?

Answer 3

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

Question 4

What is the organic matter of the bone?

Answer 4

Bone cells, collagen fibers, blood vessels and nerves

Question 5

What is the inorganic matter of the bone?

Answer 5

Ca++ and PO4 salts –> Hydroxyapatite crystals

Question 6

What is the bony matrix of the bone?

Answer 6

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

Question 7

What is an osteoprogenitor cell?

Answer 7

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

Question 8

What is an osteocyte?

Answer 8

mature bone cells maintaining bony matrix

Question 9

What is an osteoblast?

Answer 9

bone-building cells

Question 10

What is an osteoclast

Answer 10

bone-destroying cells (phagocytic lineage)

Question 11

What are the functions of the bones?

Answer 11

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

Question 12

Define tensile strength

Answer 12

Tensile strength (collagen fibers)
strength to endure stretching forces

Question 13

Define Compressional strength

Answer 13

Compressional strength (calcium salts)
strength to endure squeezing forces

Question 14

Define Bone remodeling

Answer 14

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

Question 15

What are bone turnover markers?

Answer 15

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

Question 16

Why is bone remodeling a dynamic process?

Answer 16

Bone resorption (osteoclasts) and bone formation (osteoblasts)

Question 17

What is hyaline cartilage?

Answer 17

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

2. Articular cartilage

Question 18

What is fibrocartilage?

Answer 18

Intervertebral disks, areas of tendons connected to bone, menisci

Question 19

Where is a primary ossification center?

Answer 19

Diaphysis

Question 20

Where is a secondary ossification center?

Answer 20

Epiphysis

Question 21

Define diaphysis

Answer 21

Central area of the bone

Question 22

Define epiphysis

Answer 22

Ends of the bone

Question 23

What system regulates bone physiology?

Answer 23

Endocrine system maintains plasma and bone calcium and phosphate balance:

Question 24

What hormones are involved in maintaining bones?

Answer 24

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

Question 25

How is estrogen related to bone density?

Answer 25

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

Question 26

What is PTH secretion regulated by?

Answer 26

PTH secretion follows negative feedback regulation |  Ca++ stimulates PTH release

Question 27

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

Answer 27

Bones

Question 28

How does the parathyroid gland maintain bone density?

Answer 28

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

Question 29

How does the thyroid gland maintain bone density?

Answer 29

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++

Question 30

Describe VD3

Answer 30

Cholecalciferol

Question 31

Describe VD2

Answer 31

Ergocalciferol

Question 32

True/faslse: vitamin D is not a vitamin

Answer 32

True: steroid hormone

Question 33

How much of calcium is active/free?

Answer 33

½ of circulating calcium is bound to albumin | Free, ionized calcium is physiologically active

Question 34

What are the sources of vitamin D?

Answer 34

1. Skin production (d3) from UVB/A rays (90%) | 2. jejunal absorption (D2 and D3) 10%

Question 35

What is the role of calcitonin?

Answer 35

1. Calcitonin inhibits D3 production by the kidney | 2. Inhibit bone resorption

Question 36

How is inactive D3 metabolized to active D3?

Answer 36

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

Question 37

What is the active form of Vitamin D3?

Answer 37

1,25(OH)2D3 = calcitriol

Question 38

What are the sxs of hypocalcemia?

Answer 38

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

Question 39

What is Chvostek's sign?

Answer 39

Tap over the facial nerve | Positive: twitch

Question 40

What is Trousseau's sign?

Answer 40

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

Question 41

What are the sxs of hypercalcemia?

Answer 41

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

Question 42

What is the Mnemonic: for hypercalcemia?

Answer 42

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

Question 43

What is the cause of hypercalcemia?

Answer 43

Cause of hypercalcemia is primary hyperparathyroidism caused by parathyroid adenoma

Question 44

Define osteopenia/osteoporosis

Answer 44

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

Question 45

When is peak bone mass?

Answer 45

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

Question 46

What can osteopenia/osteoporosis be caused by?

Answer 46

hyperparathyroidism

Question 47

Define osteomalacia

Answer 47

1. “Softening of bones” | 2. Weak and flexible bones d/t defective mineralization of bones

Question 48

What are the 2 main causes of osteomalacia?

Answer 48

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

Question 49

What is metabolic rickets?

Answer 49

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

Question 50

What is nutritional rickets?

Answer 50

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

Question 51

What can nutritional rickets be caused by?

Answer 51

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

Question 52

What are the physical signs of rickets?

Answer 52

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

Question 53

What are the daily requirements of vitamin D?

Answer 53

Vitamin D3 800-1,000 IU Daily

Question 54

What are the calcium carbonate/citrate daily requirements?

Answer 54

``` 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 ```

Question 55

Why does kidney failure lead to osteomalacia?

Answer 55

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

Question 56

How much calcium can a person absorb at one time?

Answer 56

500-600 mg