wk 11, lec 3

Question 1

osteogenic cells (stem cells) in bone–>
what are the 2 layers/surfaces in bone

Answer 1

endosteum (inner)
periosteum (external surface)

Question 2

periosteum (external surface)

made of?

inner cellular layer?

Answer 2

outer fibrous layer: type 1 collagen, fibroblast, blood vessels, perforatings (sharpay) fibers

inner: osteoblasts, bone lining cells, mesenchymal stem cells

Question 3

endosteum (inner body layer)

covers what?
cells?

Answer 3

covers small trabecular of bony matrix that project into marrow caviities

cells: osteoprogenitor cells, osteoblasts, osteoclasts, bone lining cells

Question 4

bone matrix is made of

Answer 4

50% inorganic material, mainly calcium
hydroxyapatite, along with bicarbonate, citrate, magnesium,
potassium, sodium, and non-crystalline calcium phosphate

organic: in calcified matrix: mostly type I collagen, proteoglycans, glycoproteins (osteonectin)

Question 5

osteoblasts are bound to bone matrix via

Answer 5

integrins

form cuboidal cell layer (adherent and gap junctions)

Question 6

what do osteoblasts produce

and what do they form

Answer 6

organic components of bone matrix (type I collagen, proteoglycan, glycoproteins)

layer of collagen-rich material (osteoid).

Question 7

what can osteoblasts differentiate into and where do they get entrapped in

Answer 7

After synthesis activity is completed, some differentiate asosteocytes entrapped in matrix-bound lacunae, some flatten and cover the matrix surface as bone lining cells,
and the majority undergo apoptosis.

Question 8

osteocytes are from

Answer 8

osteoblasts ; that get enclosed in lacunae

maintain calcified matrix, have long dendritic processes

Question 9

osteoclasts

nuclei? function?

create what?

what attaches them to bone?

what do they pump out to break down bone?

Answer 9

multinucleate; for bone resporption

create depressions in the bone
matrix called resorption lacunae or Howship lacunae.

circular sealing zone (ruffled border)

protons and enzymes

Question 10

5 types of bone

Answer 10

1. long (long diaphysis with enlarged ends/ epiphyses)
2. short (cube)
3. flat
4. irregular
5. sesamoid (small bones in tendons or joint capsules)

Question 11

4 types of bone composition

Answer 11

1. woven (newly calcified)
2. lamella (remodelled from woven)
3. compact (80% of lamellar, cortical bone)
4. cancellous (20% of lamellar, spongy bone)

Question 12

2 types of lamellar bone

Answer 12

compact/ cortical
cancellous/ spongy

Question 13

woven vs lamellar bone

Answer 13

woven is devloping and growing bones; irregular arrangement of cells and collagen, lightly calcified

lamellar is in adults and parallel bundles of collagen in thin layers (lamellae) and heavily calcified

Question 14

compact/ cortical vs calcellous/ spongy bone

which part of bones

Answer 14

compact: densely packed, thick outer region of bones (beneath periosteum)

spongy: thin trabecullae, covers the inner region, adjacent to marrow cavities

Question 15

what are the epiphyses (ends) and diaphysis (shaft) of long bones made of

Answer 15

epiphyses: cancellous/spongy bone with thin layer cover of compact bone

diaphysis: mostly compact bone with thin layer os cancellous bone around marrow cavity

Question 16

short bones made of what type of bone

Answer 16

core: cancellous/spongy bone
surrounded by compact bone

Question 17

flat bones made of what type of bone

Answer 17

two layers of
compact bone plates separated by a
thicker layer of cancellous/spongy bone.

Question 18

2 organizations of compact and cancellous bones

Answer 18

§ Mature lamellar bone
§ Woven bone

Question 19

woven bone (newly calcium, immature)

Answer 19

random arrangement of type 1 collagen

low mineral conent

high osteocytes

develops 1st in embryo

Question 20

lamellar bone

Answer 20

multiple layers/ lamellae of calcified matrix, parallel sheets or layer around central canal

organized and alternating arrangement of collagen fibers in lamellae

Question 21

osteon/ Haversian system in compact bone

central/haversian canal
volkmann canal
lacunae (house what?)
lamellae
cancaliculi (contain what?)
outer boundary?

Answer 21

layers of lamellae around central canal

cental/haversian canal has vessels, nerves, endosteum (gives nutrient and oxygen to cells in osteon)

adjacent osteons communicate via volkmann canals

between lamellae are lacunae (with osteocytes) which are spaces

canaliculi are channels that connect lacunae to each other and contain dendritic processes

outer boundary= cement line

Question 22

what remains in the osteon/haversian system after osteoclasts partially destroy osteons in bone growth and remodelling

Answer 22

interstitial lamellae = irregularly shaped groups of parallel lamellae
scattered among intact osteons.

Question 23

trabceulae in what type of bone

they dont have a haversian system

Answer 23

Trabeculae are the structural units of spongy (cancellous) bone. They form a lattice-like network of bony struts and plates, which provide support and help distribute mechanical loads.

NOT IN COMPACT BONE

Question 24

connective tissue

ECM in bone

originate from

Answer 24

fibers and ground
substance, which includes proteoglycans,
glycosaminoglycans (GAGs), and
glycoproteins like laminin and fibronectin.

embyronic mesenchyme ; mesoderm layer

Question 25

embyronyci mesenchyme --> bone what cells that

Answer 25

pluripotent stem cells become chondroblasts: (into chondrocytes) for cartilage formation fibroblasts: produce collagen and ECM components osteoblasts: form bone tissues by secreting ECM adipocytes: store fat

Question 26

cells of connective tissue

Answer 26

fibroblasts plasma cells (antibodies) lymphocytes eosinophilic leukocytes (defend against parasites, allergy rxn) neutrophilic leukocytes (phagocygtose bacteria) macrophages (phagocytose ECM and debris) mast cells and basophilic leukocytes (i.e histamine) adipocytes

Question 27

fibroblasts in bone ECM active vs inactive/quiescent

Answer 27

Synthesize and secrete collagen, elastin, GAGs, multiadhesive glycoproteins, active: irregular branch cytoplasm. RER, Golgi, euchromatic nucleus quiescent: smaller, spindle shaped, less RER, more heterochromatic nucleus

Question 28

fibroblasts in adults

Answer 28

rarely divide, but can be mitotic via growth factor i.e. wound healing, myofibroblasts

Question 29

macrophages in bone

Answer 29

from monocytes; can phagocytose

Question 30

mast cells in bone have basophilic secretory granules including

Answer 30

§ Heparin: Acts locally as an anticoagulant. § Histamine: Promotes increased vascular permeability and smooth muscle contraction. § Serine proteases: Activate various mediators of inflammation. § Chemotactic factors: Attract eosinophils and neutrophils to the site of inflammation. § Cytokines: Direct activities of leukocytes and other immune system cells. § Phospholipid precursors: Converted to prostaglandins, leukotrienes, a

Question 31

mast cells can cause

Answer 31

immediate hypersensitivity rxn --> anaphylactic shock

Question 32

plasma cells in bones

Answer 32

make antibodies

Question 33

leukocytes (WBC) in bone

Answer 33

migrate from blood into CT

Question 34

histogenesis (bone formation) for which type of bone

Answer 34

woven bone is replaced by lamellar bone (expect in skull, mandible, maxilla)

Question 35

2 process to make primary/woven bone what is the difference between

Answer 35

1. intramembranous bone formation (no cartilage intermediate) 2. endochondral bone formation (cartilage intermediate)

Question 36

intramemrbanous bone formation

Answer 36

bone from mesenchymal cells; no cartilage intermediate osteoblasts from mesenchyme and start secreting osteoid osteoprogeniot cells --> osteoblasts --> make osteoid in primary ossification center

Question 37

endochondral bone formation

Answer 37

bone formed from cartilage template --> replaced by only tissue hyline cartilage eroded and invaded by osteoblasts then start osteoid production cartilage development: chondroblasts into chondrocytes and peripheral cells into fibroblasts and form perichondrium capillaries penetrate perichondrium and mesesncymal stem cells become osteoprogenitor --> osteoblasts --> make spicules which enlarge and form thin periosteal bone collar of membrane bone chondrocyte proliferate and make stacks of flattened cells --> then hypertrophy into round superlaceunae calcify cartilage between superlacuneae chondoclasts remove dead chondrocytes and make primary marrow cavity periosteal bud ossify

Question 38

bones formed via intramembranous bone formation are called? what examples?

Answer 38

membrane bones. * Flat bones like the frontal and parietal bones * Mandible and maxilla * Scapula and clavicle * The periosteal bone collar of endochondral bones

Question 39

steps to endochondral bone formation

Answer 39

1. fetal hyaline cartilage model devleops 2. cartilage calcifies and periosteal bone collar forms around diaphysis 3. primary ossification center forms in diaphysis 4. secondary ossification cetner in epiphyses 5. bone replaces cartilage, except articular cartilage and epiphyseal plates 6. epiphyseal plates ossify and form epiphyseal lines

Question 40

ossification centers which type of bone formation? primary and secondary where? region between the centers? when ossification center enlarges and leaves a thin plate with hyaline cartilage in center? tertiary centers

Answer 40

endochondral bone formation primary OC: mid diaphysis secondary: epiphyses region btwn: metaphysis Ossification centers enlarge, leaving a thin plate with hyaline cartilage at center= epiphyseal plate tertiary OC in some bone; form bony tubercles/ ridges for muscle and ligament attachment

Question 41

first bone to ossify in humans

Answer 41

clavicle

Question 42

tertiary ossification center

Answer 42

in some bone; form bony tubercles/ ridges for muscle and ligament attachment

Question 43

region between primary and secondary ossification centers

Answer 43

metaphysis

Question 44

zones in the epiphyseal plate

Answer 44

resting zone (zone of reserve cartilage) proliferative zone (chondrocytes divide) zone of hypertrophy zone of calcification zone of ossification (osteoprogenitor cells)

Question 45

bone remodelling (secondary bone formatioN) from woven bone into lamellar bone

Answer 45

osteoclasts erode calcified cartilage and primary bone matrix vessels, nerves and lymphs invade cavity formed by erosion osteogenic cells deposit osteoblasts deposit secondary bone in lamellae (stronger, hold load) remodelling even in adults

Question 46

bone growth where to divide to get length and via which hormone girth via

Answer 46

length and girth length via chondrocyte division at epiphyseal zone of proliferation via growth hormone (esp, kids) girth via proliferation and differentiation of osteoprogenitor cells in periosteum inner layer (osteoclasts remove bone from inner surface of diaphysial so marrow cavity is enlarged and can get girth without weight gain)

Question 48

length and girth via

Answer 48

length via chondrocytes at epiphyseal zone of proliferation via growth hormone growth via proliferate and differentiation of osteoprogentior cells in inner periosteum

Question 49

bone repair

Answer 49

fractures cause vessel tears --> hemorrhage and clots macrophages and fibroblasts chondrocytes form callus with fibrocartilage and Hyaline cartilage callus replaced by primary bone from subperiosteal region --> secondary bone

Question 50

primary vs secondary osteoporosis

Answer 50

Primary osteoporosis refers to reduced bone mass and fractures in postmenopausal women or in older individuals due to age-related factors. * Secondary osteoporosis results from specific clinical disorders like thyrotoxicosis, glucocorticoid excess, and others.