bone

Question 1

describe the vascularity of bone

Answer 1

well-vascularized

Question 2

what composes the inorganic portion of bone?

Answer 2

hydroxyapatite crystals

Question 3

what composes the organic portion of bone?

Answer 3

collagen type I and ground substance

Question 4

what are the 2 layers of periosteum?

Answer 4

outer- fibrous, dense CT

inner- cellular, osteoprogenitor cells

Question 5

what is endosteum?

Answer 5

connective tissue covering the internal surfaces of bone, like aversion canals

Question 6

describe osteopblasts

Answer 6

immature bone cells that develop from osteoprogenitor cells

Question 7

what do osteoblasts secrete?

Answer 7

osteoid- organic portion of bone only (not mineralized)

Question 8

where are osteoblasts located?

Answer 8

underlying the periosteum

Question 9

what is the appearance of osteoblasts?

Answer 9

cuboidal or columnar, basophilic cytoplasm

Question 10

what are osteocytes?

Answer 10

mature bone cells

Question 11

where do osteocytes reside?

Answer 11

in lacunae

Question 12

who do adjacent osteocytes communicate?

Answer 12

via cytoplasmic processes that are housed in canaliculi

Question 13

what connects the cytoplasmic processes of osteocytes?

Answer 13

gap junctions

Question 14

what are osteoclasts?

Answer 14

bone resorbers

Question 15

what are the progenitor cells of osteoclasts?

Answer 15

share progenitor cells with monocytes, part of the mononuclear phagocyte system

Question 16

where do osteoclasts reside?

Answer 16

Howship’s Lacunae

Question 17

what is the basic appearance of an osteoclast?

Answer 17

large, multi-nucleated cell with a ruffled border

Question 18

what is the “clear zone” in osteoclasts?

Answer 18

zone around the ruffled border that is clear of organelles but abundant in actin microfilaments that allow osteoclasts to attach to bone

Question 19

how do osteoclasts break down bone?

Answer 19

through the secretion of lysosomal enzymes

Question 20

what are the 2 features of spongy bone?

Answer 20

spicules- spikes, trabecula- bridges

Question 21

describe primary bone

Answer 21

immature, irregular/unorganized collagen fibers, low mineral content, abundant osteocytes

Question 22

where is primary bone found in an adult? (3)

Answer 22

tooth sockets, near skull sutures, tendon insertions

Question 23

what are other names for primary bone?

Answer 23

immature or woven bone

Question 24

describe secondary bone

Answer 24

mature, more typical in adults, well-organized collagen fibers, contain haversian systems/lamellae

Question 25

what are other names for secondary bone?

Answer 25

mature or lamellar bone

Question 26

described haversian systems

Answer 26

concentric lamellae of collagen fibers and bone matrix, center of system in an endosteum lined canal

Question 27

what is housed in Haversian Canals?

Answer 27

blood vessels, nerves and loose CT

Question 28

what is the orientation of Haversian Canals?

Answer 28

longitudinal

Question 29

in what type of bone are Haversian systems most commonly seen?

Answer 29

compact bone

Question 30

what are Volkmann's Canals?

Answer 30

perpendicular canals that provide route for communication between Haversian Systems and communication with bone marrow

Question 31

what is the primary route for newly formed blood cells to exit bone marrow cavity?

Answer 31

volkmann's canals

Question 32

describe the 3 types of lamellae

Answer 32

outer circumferential- directly under periosteum inner circumferential- adjacent to marrow cavity interstitial- remnants of Haversian systems that have degenerated during bone remodeling

Question 33

what are the 3 general structural components of long bones?

Answer 33

diaphysis, epiphysis and metaphysis

Question 34

which part comprises the shaft?

Answer 34

diaphysis

Question 35

what is the composition of the diaphysis?

Answer 35

outer-compact bone | inner- spongy bone

Question 36

what comprises the end of long bones?

Answer 36

epiphysis

Question 37

what type of bone is the epiphysis?

Answer 37

outer- thin compact layer | inner- spongy bone

Question 38

what is another name for metaphysis?

Answer 38

growth plate

Question 39

what are the 2 important structural factors of the metaphysis?

Answer 39

highly vascularized and innervated

Question 40

what is an example of a long bone?

Answer 40

humerus, femur, etc

Question 41

what is an example of short bone?

Answer 41

metacarpals

Question 42

what are the structural characteristics of short bone?

Answer 42

outer- compact bone | inner- spongy bone

Question 43

where are flat bones found?

Answer 43

skull

Question 44

what is the general structure of flat bones?

Answer 44

outer-compact bone (plates) | inner- spongy bone (dipole)

Question 45

what type of bone undergoes intramembranous ossification?

Answer 45

flat bones

Question 46

why is is called "intramembranous ossification"?

Answer 46

because mesenchymal cells condense to form a membrane

Question 47

what do mesenchymal cells differentiate into in intramembranous ossification?

Answer 47

osteoblasts, to form primary ossification center

Question 48

what is the method for most long and short bone formation?

Answer 48

endochondral ossification

Question 49

what forms the scaffolding in endochondral ossification?

Answer 49

hyaline cartilage

Question 50

where is the primary ossification center in long bones?

Answer 50

diaphysis

Question 51

what happens to the perichondrium in endochondral ossification?

Answer 51

perichondrium becomes highly vascularized allowing for differentiation of chondrogenic cells to osteoprogenitor cells to osteoblasts

Question 52

what happens to the perichondrium once osteoblasts are present?

Answer 52

it is renamed to periosteum

Question 53

what is the bone collar?

Answer 53

structure at primary ossification center that is formed by osteoblasts. located just deep to periosteum

Question 54

through what process does the bone collar form?

Answer 54

through intramembranous ossification

Question 55

what are one marrow spaces formed from?

Answer 55

chondrocytes that hypertrophy and degenerate, the coalescence of their lacuna form marrow spaces

Question 56

where are the blood vessels found in forming bone?

Answer 56

osteogenic bud

Question 57

how does forming bone access the osteogenic bud?

Answer 57

osteoclasts eat away the bone collar

Question 58

in what direction does the diaphysis grow?

Answer 58

toward the epiphysis

Question 59

where is the secondary ossification center?

Answer 59

epiphysis

Question 60

what is another name for secondary ossification?

Answer 60

closure of growth plate

Question 61

does secondary ossification center have a bone collar?

Answer 61

NO

Question 62

after growth plates close, what 2 places retained their cartilage?

Answer 62

articular surfaces and epiphyseal plate

Question 63

name the 5 zones of the epiphyseal plate

Answer 63

``` Resting Cartilage Proliferation Hypertrophy Calcification Ossification ```

Question 64

what is occurring at the zone of resting cartilage?

Answer 64

nothing! contains resting hyaline cartilage

Question 65

what is occurring at the zone of proliferation?

Answer 65

chrondrocytes proliferate, sometimes with "coin stack" appearance

Question 66

what is occurring at the zone of hypertrophy?

Answer 66

chrondrocytes enlarge before they die and lose their ability to maintain normal cellular functioning

Question 67

what is occurring at the zone of calcification?

Answer 67

chondrocytes degenerate and the cartilage matrix that surrounded the chondrocytes begin to calcify, often appears basophilic

Question 68

what is occurring at the zone of ossification?

Answer 68

osteoblasts present, depositing bone matrix on the cartilage scaffold, acidophilic

Question 69

when are osteoblasts renamed osteocytes?

Answer 69

when they are entirely surrounded by matrix (housed in lacunae)

Question 70

how does bone grow in width?

Answer 70

appositional growth

Question 71

describe the 6 steps of fracture repair

Answer 71

``` blood clot forms periosteum and endosteum proliferate hyaline cartilage forms primary bone is laid down bone callus unites fracture remodeling occurs ```

Question 72

what is the purpose of PTH?

Answer 72

raise blood calcium

Question 73

how does PTH raise blood calcium?

Answer 73

activates osteoprogenitor cells to make more cells, more osteoclasts are formed and bone resorption occurs (indirect mechanism)

Question 74

what is the purpose of calcitonin?

Answer 74

lower blood calcium

Question 75

how does calcitonin lower blood calcium?

Answer 75

stabilizes bone by inhibiting osteoclasts (direct)

Question 76

what is the role of estrogen in bone?

Answer 76

estrogen limits excessive bone resorption

Question 77

how does estrogen limit bone resorption?

Answer 77

inhibition of osteoclasts, regulation of osteoblasts

Question 78

how does menopause affect bone density?

Answer 78

estrogen levels decrease in menopause, allows increased bone resorption

Question 79

what is the effect of estrogen on OPG?

Answer 79

estrogen upregulates OPG

Question 80

what is the effect of estrogen on OPGL?

Answer 80

estrogen down regulated OPGL

Question 81

describe osteopetrosis

Answer 81

defective bone resorption, osteoclasts lack ruffled borders

Question 82

describe osteitis fibrosa cystica

Answer 82

abnormally high osteoclast activity

Question 83

describe osteomalacia

Answer 83

impaired mineralization leading to weak bones, can be 2/2 calcium deficiency

Question 84

what type os cancer frequently met to bone?

Answer 84

prostate, breast and lung

Question 85

what is a benign bone tumor?

Answer 85

osteoblastoma

Question 86

what is a malignant bone tumor?

Answer 86

osteosarcoma

Question 87

what are he histologic characteristics of woven bone?

Answer 87

few osteons, larger osteocytes, irregular collagen bundles