Bone histology

Question 1

what are the components of the bone matrix?

Answer 1

organic (35%) = collagen and proteoglycans
inorganic (65%) = hydroxyapatite
mineral components = weight bearing strength
collagen = flexible strength

Question 2

how do the components of the bone matrix contribute to bone flexibility and bones’ ability to bear weight?

Answer 2

mineral is reduced,collagen is increased = bone is flexible

collagen is reduced, mineral is increased = bone is very brittle

Question 3

what are the characteristics and functions of osteoblasts?

Answer 3

bone building cells; produce collagen and proteoglycans, which are packaged into vesicles by the golgi apparatus and secreted by exocytosis; also secrete matrix vesicles

Question 4

what are the characteristics and functions of osteocytes?

Answer 4

osteoblasts become osteocytes; osteocyte cell bodies can be found in the lacunae; and their cell extensions are housed in narrow, long spaces = canaliculi

Question 5

what are the characteristics and functions of osteoclasts?

Answer 5

bone destroying cells; derived from stem cells red bone marrow

Question 6

what are the names of the spaces that are occupied by osteocyte cell bodies and cell extensions?

Answer 6

osteocyte cell bodies = lacunae

cell extensions = canaliculi

Question 7

what cells give rise to osteochondral progenitor cells?

Answer 7

mesenchymal cells

Question 8

what kind of cells are derived from osteochondral progenitor cells?

Answer 8

osteoblasts

Question 9

what types of cells give rise to osteoclasts?

Answer 9

the stem cells from red bone marrow

Question 10

how is the organization of collagen fibers different in woven and lamellar bone?

Answer 10

in woven bone, the cartilage fibers are randomly oriented in many directions; in lamellar bone, cartilage fibers lie parallel to one another, but at an angle they lie in a adjacent lamellae

Question 11

what process produces woven bone?

Answer 11

ossification

Question 12

what are trabeculae and what is their function?

Answer 12

interconnecting rods or plates of bone; provides strength and transfer external load away from the joint and toward the cortical bone

Question 13

how do osteocytes within trabecule obtain nutrients?

Answer 13

they obtain their nutrients through the canaliculi

Question 14

what is an osteon?

Answer 14

functional unit of a long bone; also known as haversian system

Question 15

what are the names of the 3 types of lamellae found in compact bone?

Answer 15

concentric lamellae, circumferential lamellae, and interstitial lamellae

Question 16

matrix vesicles

Answer 16

contain high concentration of calcium and phosphate; when these reach a certain level hydroxyapatite crystals form

Question 17

ossification

Answer 17

formation of new bone by osteoblasts; occurs by appositional growth on the surface of existing material, either bone or cartilage; can occur as a fetus, when growing, or in bone repair

Question 18

hydroxyapatite crystals

Answer 18

acts as template that stimulates hydroxyapatite formation and mineralization of the matrix

Question 19

bone reabsorption

Answer 19

breakdown of bone; important for mobilizing crucial calcium and phosphate ions for use in many metabolic processes; as bone breaks down the calcium goes back to the bloodstream

Question 20

podosomes

Answer 20

develop and form a sealed compartment under the osteoclast

Question 21

ruffled border

Answer 21

specialized reabsorption-specific area of the membrane; acidic vesicles fuse with membrane of ruffled border, while ATP-powered H+ pumps and protein-digesting enzymes are inserted into the membrane of ruffled border

Question 22

woven bone

Answer 22

formed first, weak, osteoclasts will break down and osteoblasts build lamellar bone

Question 23

lamellar bone

Answer 23

mature bone - arranged in concentric sheets called lamellae

Question 24

what are the two types of bone formed during ossification

Answer 24

woven and lamellar bone

Question 25

spongy bone

Answer 25

has less bone matrix and more space; spaces are filled with bone marrow/blood vessels; prominent in areas of bones that are not heavily stressed or where stresses arrive from many directions

Question 26

compact bone

Answer 26

more bone matrix and less space

Question 27

concentric lamellae

Answer 27

oriented around the central canal; rings of bone matrix

Question 28

circumferential lamellae

Answer 28

thin plates extend around bone

Question 29

interstitial lamellae

Answer 29

remnants of concentric/circumferential lamellae that were removed during bone remodeling

Question 30

perforating canals

Answer 30

deliver blood to central canal –> run perpendicular, deliver nutrients/remove waste to osteocytes –> canaliculi