Cartilage and Bone Flashcards

1
Q

Cartilage consists of

A

cells (chondrocytes), ground substance, extracellular fibers

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2
Q

Histology of cartilage

A

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

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3
Q

Shock absorbing characterstic of hyalin cartilage

A

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

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4
Q

Rigidity of hyalin cartilage

A

Due to interactions between type 2 collagen fibrils and GAGs

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5
Q

GAG

A

glycosaminoglycans: proteoglycans in cross linked matrix with hyaluronic acid

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6
Q

matrix components of cartilage

A

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

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7
Q

synthesis of GAG

A

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

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8
Q

cartilage nutrition

A

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

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9
Q

3 types of bone cells

A

osteoblasts, osteoclasts, osteocytes

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10
Q

two types of long bones

A

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

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11
Q

compact bone

A

lamellar, cortical; dense area without cavities

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12
Q

cancellous bone

A

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

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13
Q

geography of long bone

A

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

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14
Q

composition of bone matrix

A

35% organic matrix and 65% inorganic salts

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15
Q

organic matrix of bone

A

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

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16
Q

inorganic content

A

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

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17
Q

osteoprogenitor cells

A

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

18
Q

osteblasts

A

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

19
Q

osteocytes

A

calcified osteoblasts; communicate via gap junctions

20
Q

osteoclasts

A

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

21
Q

origin of bone cells

A

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

22
Q

osteoblasts synthesize

A

osteoid, alkaline phosphatase, noncollagenous proteins

23
Q

osteoid

A

type 1 collagen and proteoglycans

24
Q

noncollagenous proteins synthesized by noncollagenous proteins

A
RANK-L- stimulated osteoclastogenesis
Osteoprotegerin inhibiting factor- decoy receptor for RANK-L
growth factors
osteocalcin- mineralization
osteopontin- forms sealing zones
25
skull
external table, diploe, internal table
26
architecture of long bone
periosteum and endosteum
27
periosteum
bone is surrounded by dense CT- has osteoprogenitor cells | absent at articulating surfaces and at attachment of tendons and ligaments
28
endosteum
lining the marrow cavity and have osteoprogenitor cells lining
29
ground substance
glycoproteins, glycosaminoglycans, proteoglycans, GF, peptides calcium phosphate magnesium phosphate
30
ARF cycle
activation--> resorption (by osteoclasts)--> reversal (osteoblasts grow)--> formation--> resting phase--> activation
31
PTH
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)
32
Calcitonin
opposite of PTH; C cells of thyroid gland and decreases serum Ca++
33
osteoclasts in presence of PTH
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)
34
bisphosphonates
kill osteoclasts via apoptosis; inhibits osteoclast recruitment
35
MCSF and OPG
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
36
types of cartilage
hyaline, elastic, fibrocartilage
37
hyaline cartilage
in external auditory meatus, cartilage models of long bones; type 2 collagen; perichondrium (dense CT surrounding cartilage)
38
elastic cartilage
in pinna of ear and larynx; type 2 collagen and elastic fibers; perichodnrium
39
fibrocartilage
in intervertebral disks, pubic symphysis; type 1 collagen, no perichondrium
40
vitamin D
decrease in vitamin D increases calcium secretion from bones; vitamin D inhibits PTH
41
denosumab
inhibits rank-L