Cartilage and Bone

Question 1

Cartilage consists of

Answer 1

cells (chondrocytes), ground substance, extracellular fibers

Question 2

Histology of cartilage

Answer 2

pink background- matrix; dark pink and provides blood supply- perichondrium; gaps- lacunae housing the chondrocytes

Question 3

Shock absorbing characterstic of hyalin cartilage

Answer 3

Due to water binding to negatively charged proteoglycans and is squeezed out of cartilage upon compression and comes back and binds to proteoglycan again when relaxed

Question 4

Rigidity of hyalin cartilage

Answer 4

Due to interactions between type 2 collagen fibrils and GAGs

Question 5

GAG

Answer 5

glycosaminoglycans: proteoglycans in cross linked matrix with hyaluronic acid

Question 6

matrix components of cartilage

Answer 6

GAGs (chondroitin 4 sulfate, chondroitin 6 sulfate, keratan sulfate, and hyaluronic acid) and adhesive molecule (chondronectin)

Question 7

synthesis of GAG

Answer 7

amino acids put together in the RER and sugars added in golgi apparatus

Question 8

cartilage nutrition

Answer 8

cartilage lacks vasculature so nutrients must come in through diffusion; nutrients provided via perichondrium

Question 9

3 types of bone cells

Answer 9

osteoblasts, osteoclasts, osteocytes

Question 10

two types of long bones

Answer 10

compact, lamellar, or cortical bone; cancellous (trabecular) bone

Question 11

compact bone

Answer 11

lamellar, cortical; dense area without cavities

Question 12

cancellous bone

Answer 12

3-d lattice of branching bony spicules, forming tabeculae around narrow spaces

Question 13

geography of long bone

Answer 13

epiphyses- two ends
diaphysis- shaft
metaphysis- growth plate between epiphyses and diaphysis

Question 14

composition of bone matrix

Answer 14

35% organic matrix and 65% inorganic salts

Question 15

organic matrix of bone

Answer 15

35% of bone; extracellular organic phase, composed of proteins (exogenously derived and trapped growth factors), glycoproteins, and proteoglycans synthesized by the osteogenic cell;
consists of type 1 collagen fibers (85-90%) embedded in an amorphous ground substance

Question 16

inorganic content

Answer 16

65%; hydroxyapatite crystals [Ca10(OH2)(PO4)6]

Question 17

osteoprogenitor cells

Answer 17

pluripotential, stem cells from mesenchyme; can differentiate into osteogenic cells-osteoblasts; found in periosteum and endosteum as bone lining cells and differentiate into osteoblasts following a fracture

Question 18

osteblasts

Answer 18

synthesize and secrete the organic matrix of bone: type 1 collagen and non collagenous proteins and alkaline phosphatase

Question 19

osteocytes

Answer 19

calcified osteoblasts; communicate via gap junctions

Question 20

osteoclasts

Answer 20

multinucleated cells derived from monocytes; produce an acidic environment ideal for dissolution of bone matrix; plasmalemma of the osteoclast is thrown into folds and villous like processes constituting the ruffled border

Question 21

origin of bone cells

Answer 21

mesenchyme–> osteoprogenitor –>osteoblasts (–> osteocytes) OR bone lining cells (stem cells);
bone marrow monocyte precursors–> monocytes–> osteoclasts

Question 22

osteoblasts synthesize

Answer 22

osteoid, alkaline phosphatase, noncollagenous proteins

Question 23

osteoid

Answer 23

type 1 collagen and proteoglycans

Question 24

noncollagenous proteins synthesized by noncollagenous proteins

Answer 24

RANK-L- stimulated osteoclastogenesis
Osteoprotegerin inhibiting factor- decoy receptor for RANK-L
growth factors
osteocalcin- mineralization
osteopontin- forms sealing zones

Question 25

skull

Answer 25

external table, diploe, internal table

Question 26

architecture of long bone

Answer 26

periosteum and endosteum

Question 27

periosteum

Answer 27

bone is surrounded by dense CT- has osteoprogenitor cells

absent at articulating surfaces and at attachment of tendons and ligaments

Question 28

endosteum

Answer 28

lining the marrow cavity and have osteoprogenitor cells lining

Question 29

ground substance

Answer 29

glycoproteins, glycosaminoglycans, proteoglycans, GF, peptides
calcium phosphate
magnesium phosphate

Question 30

ARF cycle

Answer 30

activation–> resorption (by osteoclasts)–> reversal (osteoblasts grow)–> formation–> resting phase–> activation

Question 31

PTH

Answer 31

parathyroid hormone; decreased blood calcium stimulates PTH–> bone releases calcium by increasing osteoclasts and ruffled border activity–> kidneys conserve Ca++–> intestine absorbs Ca++;

increased blood calcium inhibits PTH secretion (inhibitory)

Question 32

Calcitonin

Answer 32

opposite of PTH; C cells of thyroid gland and decreases serum Ca++

Question 33

osteoclasts in presence of PTH

Answer 33

do not have receptor for PTH; osteoblasts release RANK-L which binds to RANK on osteoclasts and pre-osteoclasats which increases activity of ruffle border
(osteoprotegrin counter RANK-L)

Question 34

bisphosphonates

Answer 34

kill osteoclasts via apoptosis; inhibits osteoclast recruitment

Question 35

MCSF and OPG

Answer 35

1. Monocytes derived from vessels in the bone marrow express M-CSF receptor on their cell surface. 2. M-CSF binds to M-CSF receptor and induces the expression of RANK. 3. RANK ligand (RANKL) is produced by stromal cells/osteoblasts and binds to the receptor, RANK, on mononuclear osteoclast progenitors. 4. OPG, a decoy receptor that binds to RANKL and inhibits osteoclast differentiation. 5. Multiple factors including hormones and locally produced cytokines/growth factors and matrix proteins, mediate the ­activation (bone resorption) of osteoclasts

Question 36

types of cartilage

Answer 36

hyaline, elastic, fibrocartilage

Question 37

hyaline cartilage

Answer 37

in external auditory meatus, cartilage models of long bones; type 2 collagen; perichondrium (dense CT surrounding cartilage)

Question 38

elastic cartilage

Answer 38

in pinna of ear and larynx; type 2 collagen and elastic fibers; perichodnrium

Question 39

fibrocartilage

Answer 39

in intervertebral disks, pubic symphysis; type 1 collagen, no perichondrium

Question 40

vitamin D

Answer 40

decrease in vitamin D increases calcium secretion from bones; vitamin D inhibits PTH

Question 41

denosumab

Answer 41

inhibits rank-L