Bones and connective tissues Flashcards
1
Q
synovial joint motions
A
gliding/linear; angular (may be abduction, adduction, flexion, extension, or circumduction); rotation
2
Q
synovial joint types
A
gliding (surfaces slide across each other), hinge (movement in single plane), pivot (rotation between apposing parts), saddle, ellipsoid/condyloid (knuckle-like; oval face apposes a depression), ball-and-socket; all possess a cavity between the bones comprising the joint; apposing surfaces of each bone are covered by articular cartilage; joint is surrounded by a fibrous capsule that is lined internally with a synovial membrane that secretes lubricative fluid
3
Q
concentric contraction
A
a type of isotonic contraction; occurs when the muscle shortens
4
Q
eccentric contraction
A
a type of isotonic contraction; occurs when the muscle lengthens while contracting; involves a controlled but gradual relaxation that generates diminishing force or tension
5
Q
isotonic contraction
A
when a skeletal muscle changes length as it generates force
6
Q
isometric contraction
A
when a skeletal muscle creates tension or force without movement or change in length
7
Q
muscle tone
A
slight amount of contraction that a muscle maintains even when relaxed in a conscious individual; lost when an individual is unconscious or has a nerve lesion causing paralysis
8
Q
prime mover/agonist
A
the muscle or muscle group primarily responsible for the initiation and execution of a specific action at a joint; may be gravity
9
Q
antagonist
A
muscle or muscle group that opposes or reverses the action of a prime mover; may act to stabilize the movement of the agonist
10
Q
synergist
A
muscle or muscle group that assists the prime mover in its action(s); may provide additional pull at the origin, reduce some undesirable movements that the prime mover incidentally induces, hold a bone in place so that the prime mover has a stable base, or produce force simultaneously in a different direction to produce a rotation
11
Q
fixator/stabilizer
A
a type of synergist that holds a bone in place so that the prime mover has a stable base
12
Q
electromyography
A
Analysis of motor unit action potentials (MUAPs) and baseline electrical signal at rest in order to assess the health of a muscle and its innervating nerve
13
Q
hyaline cartilage
A
most common type of cartilage; contains round or oval chondrocytes surrounded by pericellular matrix; usually surrounded by perichondrium; forms nasal, costal, laryngeal, bronchial, and articular cartilage; serves as a template for endochondral ossification; also present in epiphyseal plate cartilage
14
Q
elastic cartilage
A
yellowish when fresh due to presence of elastin; usually surrounded by perichondrium; forms auricular, auditory, laryngeal, and epiglottal cartilage
15
Q
articular cartilage
A
a specialized type of hyaline cartilage that has no perichondrium and covers the articulating surfaces of opposing bones in a joint; arranged in three zones - most superficial has collagen fibers arranged parallel to the surface, middle has fibers arranged obliquely, and deepest has fiber arranged perpendicular to the surface with mineralized cartilage matrix; thick band of mineralized matrix (tidemark) separates mineralized zone from more superficial zones
16
Q
fibrocartilage
A
white and opaque due to predominance of type I collagen; contains bundles of collagen with chondrocytes arranged in a linear fashion parallel to collagen bundles; has no perichondrium; forms intervertebral disks, symphases, tendon insertions, and articular disks; also forms calluses during healing of a bone fracture
17
Q
chondrocyte
A
cells found in cartilage that are embedded within the cartilage matrix; round, have basophilic cytoplasm, found in clusters called isogenous groups/cell nests; can divide, but less frequently as they age; produce components of cartilage matrix and enzymes that degrade cartilage matrix
18
Q
aggrecan
A
predominant proteoglycan monomer found in cartilage ground substance; generally bound to a central hyaluronate backbone to form multi molecular proteoglycan aggregates
19
Q
lacunae
A
cavities between concentric lamellae of bone osteons where osteocytes reside; also used to describe spaces in cartilage matrix where chondrocytes reside
20
Q
perichondrium
A
outer layer of cartilage elements that encloses the cartilaginous structures; outer part is made of fibrous connective tissue (type I cartilage) secreted by fibroblasts and contains a capillary plexus, nerves, and lymphatics; inner part is made of chondrogenic cells that may become chondroblasts
21
Q
cartilage-specific collagens
A
fibers that make up the fibrous component of cartilage matrix; give mechanical stability to the ground substance; type II collagen is predominant isoform; also includes types IX, X, and XI
22
Q
appositional growth
A
type of cartilage growth in which it grows from within; caused by division of chondrocytes followed by separation due to matrix production; important for growth of long bones; generally occurs in young cartilage
23
Q
interstitial growth
A
type of cartilage growth in which it grows from the surface; caused by chondrogenic cells inside the perichondrium differentiating into chondroblasts that express SOX 9, which subsequently secrete cartilage matrix and become enclosed within in
24
Q
territorial matrix
A
cartilage matrix found in hyaline cartilage immediately surrounding chondrocytes; contains thin collagen fibers
25
interterritorial matrix
cartilage matrix found in hyaline cartilage in spaces between chondrocytes; contains thick collagen fibers and most of the proteoglycan
26
proteoglycan
contribute to the organic component of bone, along with collagen I and glycoproteins, though they exist in higher amounts in cartilage
27
glycosaminoglycan
macromolecular component of cartilage matrix; proteoglycans attached to core proteins, which are in turn attached to a hyaluronate backbone
28
hydroxyapatite
crystalized calcium phosphate that makes up the inorganic component of bone; forms alongside collagen I fibrils; primary mediator of the hardness of bone
29
osteoid
organic bone matrix; makes up 30% of total bone matrix; consists of type I collagen, proteoglycans, and glycoproteins secreted by osteoblasts; mediates calcification of bone
30
woven bone
AKA primary bone; weak, immature bone that is less organized than secondary bone; seen in developing or regenerating bone; during development, is resorbed and remodeled to produce secondary bone
31
compact bone
areas of bone that are dense and have no cavities; makes up cortical bone, in which 80-90% of volume is calcified; fulfills primarily a mechanical and protective function
32
trabecular bone
AKA spongy or cancellous bone; areas of bone that are highly trabeculated and caveated; 15-25% of volume is calcified, fulfills mainly a metabolic function (calcium reservoir); only makes up 20% of total bone volume but accounts for 80% of bone turnover/remodeling due to higher SA:volume ratio
33
lamellar bone
bone that is made up of osteons organized from concentric lamellae
34
canaliculi
tiny canals within bone osteons that connect lacunae in adjacent lamellae and contain osteocyte dendrites
35
osteocyte
differentiated osteoblasts; occupy lacunae that lie between lamellae of the bone matrix; function as endocrine cells and mechanosensor cells to regulate bone remodeling; communicate with neighboring cells via dendrites and gap junctions; express dental matrix protein 1 (DMP1) and sclerostin (SOST)
36
osteoblast
activated osteoprogenitor cells, located primarily in the inner layer of the periosteum (but some in the endosteum); mediate appositional growth of bone; differentiate under the influence of bone morphogenic proteins (BMPs), and are differentiated from other fibroblasts by the presence of Runx2 (bone master gene transcription factor) and osteocalcin; differentiate under the influence of Wnt/Beta-catenin signaling and RUNX2; primary protein product is type I collagen; also secrete osteoprogegerin (inhibits osteoclast differentiation) and SIBLING family proteins (modulators of mineralization)
37
osteoclast
large multinuclear cells that originate in the bone marrow and differentiate from the monocyte/macrophage lineage based on combinatorial signaling (M-CSF, RANKL, CTR, TRAP); occupy Howship's lacunae on the endosteal surface of bone; activated by PTH and 1,25-OH-D and inhibited by calcitonin; destroy bone matrix and facilitate remodeling via secretion of protons (acid) and cathepsin-K
38
ruffled border
specialized cellular membrane that osteoclasts use to attach to bone matrix and create a microenvironment in which to resorb bone
39
Haversian canal
central canal in bone osteon surrounded by concentric lamella; transmits blood vessels, nerves, and lymphatics
40
Volkmann canal
canals in bone osteons that are continuous with the Haversian canal and connect adjacent lamellae; transmits blood vessels, nerves, and lymphatics
41
intramembranous ossification
primary method by which flat bones ossify; bone forms from ossification centers, where mesenchymal stem cells condense and differentiate into osteoblasts within reticular connective tissue, which allows deposition of bone matrix and ultimate incorporation of osteocytes into lacunae; process by which fontanelles in neonates are ossified
42
endochondral ossification
primary method by which long bones ossify; osteoblasts deposit bone on pre-existing hyaline cartilage template; begins with a primary ossification center in the diaphysis that leads to intramembranous ossification around the perichondrium; cartilage cells then hypertrophy; this allows osteoblasts to produce bone on calcified cartilage with concomitant cavitation; cycle repeats at epiphyses, where some hyaline cartilage is retained, both as articular cartilage and epiphyseal plate cartilage
43
epiphyseal plate
layer of hyaline cartilage found at the epiphyses of long bones
44
reserve zone
part of the epiphyseal plate; does not participate in bone growth; resident chondrocytes connect the epiphyseal plate to the osseous tissue of the epiphysis
45
proliferative zone
one of the zones of epiphyseal activation in the epiphyseal plate; sustained by IGF-1; makes cartilage matrix (type II collagen)
46
hypertrophy zone
one of the zones of epiphyseal activation in the epiphyseal plate; zone where chondrocytes enter apoptotic phase; susceptible for fractures, and is responsible for 20% of fractures in children
47
calcification zone
one of the zones of epiphyseal activation in the epiphyseal plate; chondrocyte proliferation is inhibited, type X collagen is synthesized, and hydroxyapatite formation begins; strongly basophilic
48
bone remodeling
bone synthesis and removal; occurs throughout the lifespan
49
bony callus
structure synthesized by osteoblasts during repair of bone fractures; replaces the fibrocartilaginous callus previously laid down by fibroblasts and chondroblasts, ultimately replaced by mature bone as it heals
50
mesenchymal stem cells
stem cells that may differentiate into osteoblasts or chondroblasts; population declines with age
51
osteoarthritis
family of degenerative joint diseases; characterized by progressive loss of articular cartilage; symptoms include chronic pain, joint deformity, and eventual disabilty
52
rheumatoid arthritis
disease caused by an inflammatory reaction against the synovium of joints; may lead to destruction of the joint; mediated by cytokines (i.e. IL-1, TNF-alpha) that stimulate release of proteases from chondrocytes and inflammatory cells, resulting in degradation of core proteins in proteoglycan aggregates
53
osteisis fibrosa cystia
a condition in which osteoclasts destroy bone matrix as it is made
54
Paget's disease
a condition that affects adults over 40 y.o. in which abnormal osteoclasts cause a high rate of remodeling, resulting in an over-abundance of primary/woven bone; can cause pain, nerve entrapment, and weakening of affected areas; remodeling regulation disease
55
osteoporosis
condition characterized by hollow, fragile bones due to osteoclast-mediated resorption that occurs faster than osteogenesis; for every 10% loss in bone mass, the risk of fracture doubles
56
osteopetrosis
condition characterized by growth of dense, heavy bone that lacks lamellar structure (woven bone) due to immature osteoclasts that lack a ruffled membrane; may cause obliteration of bone marrow cavity and subsequent bone marrow suppression
57
anti-resorptive drugs
class of drugs used in the treatment of osteoporosis that prevent bone resorption/osteoclast differentiation; various classes include SERMs, bisphosphonates, and denosumab (binds RANKL)
58
anabolic drugs
class of drugs used in the treatment of osteoporosis that induces osteoblast differentiation; only FDA-approved drug in this class is teriparatide, or PTH 1-34; mimics PTH activity, such that daily spikes (due to daily administration) promote osteoblast induction
59
BMP-2/BMP-7
growth factors that induce stem cells in bone marrow to differentiate into osteoblasts; clinical trials have used recombinant BMPs to assist bone regeneration in patients
60
bisphosphonates
class of anti-resorptive drugs used in the treatment of osteoporosis; examples include alendronate, risedronate, ibandronate
61
SERMs
selective estrogen receptor modulators; class of anti-resorptive drugs used in the treatment of osteoporosis; example includes raloxifene
62
osteoprotegerin
protein secreted by PTH-stimulated MSCs and osteoblasts that inhibits osteoclast development by binding RANKL
63
RANKL
cell surface receptor expressed by PTH-stimulated MSCs that induces osteoclast development
64
M-CSF
cytokine that induces monocyte/macrophage proliferation and contributes to osteoclast development
65
leptin
hormone made by fat cells; induces the CNS to inhibit bone formation
66
IGF I
insulin-like growth factor 1; synthesized by the liver in response to somatotropin signaling
67
collagen I
part of the organic component of bone, along with proteoglycans and glycoproteins; arranged in an anti-helical fashion that helps mediate the hardness of bones
68
collagen X
synthesized by chondrocytes in the calcification zone of the epiphyseal plate; facilitates beginning of hydroxyapatite formation, later replaced by collagen I from osteoblasts
69
cathepsin-K
lysosomal enzyme secreted by osteoclasts that is activated by a low pH and facilitates breakdown of bone matrix during remodeling
70
parathyroid hormone
hormone secreted by the parathyroid that stimulates osteoclasts to facilitate bone resorption and calcium release
71
calcitonin
hormone that inhibits osteoclasts to prevent bone resorption
72
osteocalcin
glycoprotein that is specific to bone and promotes its mineralization
73
estrogen
sex hormone that stimulates somatotropin release from the pituitary gland; estradiol also decreases chondrocyte GAG synthesis
74
testosterone
sex hormone that stimulates somatotropin release from the pituitary gland; also induces chondrocyte GAG synthesis
75
somatotropin
AKA growth hormone; secreted by the pituitary gland in response to estrogen and/or testosterone stimulation; induces the liver to make insulin-like growth factor 1 (IGF-1); also induces chondrocyte GAG synthesis
76
glycoproteins
contribute to the organic component of bone, along with collagen I and proteoglycans; includes glycosylated proteins that promote calcification, esp. osteocalcin
77
noncollagenous multiadhesive glycoproteins
components of cartilage matrix; consist of small regulatory and structural proteins that influence interaction between chondrocytes and the ECM; examples include chondronectin, tenascin, and anchorin CII; clinically valuable as markers of cartilage turnover and degradation
78
Heinemann size principle
in a given movement/muscle contraction, the smallest motor units fire first, followed by recruitment of larger motor units as the firing frequency of the first units increases to a particular threshold
79
uricosuric
drug that increases the rate of excretion of uric acid; class of drugs commonly used in the treatment of gout
80
disease-modifying anti-rheumatic drugs (DMARDs)
class of drugs used in treatment of RA that slow down or stop joint damage; generally biological response modifiers/biologics
81
allopurinol
used in the treatment of gout; structural analog of hypoxanthine, converted to oxypurinol by aldehyde oxidoreductase, inhibits terminal steps in uric acid biosynthesis by blocking xanthine oxidase; oxypurinol has very long half-life; side effects include hypersensitivity rxns, acute gout attacks (decreased plasma uric acid levels mobilizes tissue stores of uric acid - generally co-administered with colchicine or NSAID); inhibits metabolism of azathioprine and mercaptopurine
82
adalimumab
IgG mAb used in the treatment of RA and juvenile idiopathic arthritis; anti-TNF-alpha, binds both soluble and transmembrane forms to prevent it from binding its receptor (binding transmembrane forms may also induce apoptosis of the secreting cell); long half-life; side effects include injection site rxns, increase susceptibility to infection; may be used alone or in combination with methotrexate
83
colchicine
used in the treatment of gout for acute attacks or prophylactically; arrests cell division in G1 by interfering with microtubule formation (blocks polymerization), which inhibits neutrophil activation and migration (i.e. inflammation); rapidly absorbed orally, large volume of distribution, has a narrow therapeutic-toxicity window; metabolized by CYP450s and is a substrate for P-glycoprotein; side effects include GI irritation (affects rapidly-proliferating cells); contraindicated in those with hepatic or renal disease, elderly, and pts taking CYP3A4/P-gp inhibitors
84
etanercept
recombinant fusion protein used in the treatment of RA and juvenile RA; made up of two soluble TNF p75 receptor moieties linked to Fc portion of human IgG; binds soluble TNF-alpha and inhibits its ability to bind its receptor; long half-life; side effects include injection site reactions and increased susceptibility to infection
85
febuxostat
used in the treatment of gout; non-purine xanthine oxidase inhibitor; more potent than allopurinol, more effective in patients with impaired renal function; similar incidence of most side effects (dizziness, diarrhea, headache, nausea) is similar to allopurinol, but incidence of cardiovascular side effects is higher; inhibits metabolism of azathioprine and mercaptopurine
86
azathioprine
immunosuppressive drug used in the treatment of RA; inhibits de novo purine synthesis (6-mercaptopurine prodrug, guanine analog)
87
pegloticase
used in the treatment of gout; pegylated, recombinant form of uricase; converts uric acid to allantoin, an inactive and water-soluble metabolite; side effects include infusion site reactions, gout flare, immune response to PEG; only used in severe cases of gout refractory to other treatment
88
abatacept
fusion protein used in the treatment of adult RA in pts with inadequate response to one or more DMARD/TNF antagonist; contains endogenous ligand CTLA-4, binds CD80 or CD86 on antigen-presenting cells (prevents activation by CD28); long half-life; side effects include injection site rxn, increased susceptibility to infection
89
probenecid
uricosuric drug used in the treatment of gout; increases uric acid excretion by competing with renal tubular acid transport to prevent rate reabsorption (OAT/URAT1); side effects include GI irritation, ineffectiveness in pts with renal insufficiency; contraindicated in pts with uric acid kidney stones; interferes with renal excretion of other drugs that undergo active tubular secretion (esp. weak acids)
90
rituximab
mAb used in the treatment of adult RA in combination with methotrexate in pts with inadequate response to one or more TNF antagonists; anti-CD20, depletes B cells via complement-dependent cytotoxicity and antibody-dependent cytotoxicity; long half-life; side effects include injection site rxns, increased susceptibility to infection
91
NSAID
used for treatment of gout (w/i 24 hrs of onset of acute attack); also used for RA in large doses for long duration, but does not affect disease progression; also used for osteoarthritis
92
tocilizumab
mAb used in the treatment of adult RA (pts who have had inadequate response to one or more TNF antagonists); anti-IL-6R, binds both soluble and membrane-bound receptor to inhibit IL-6-mediated signaling via receptors (normally activates T-cells, B-cells, macrophages, and osteoclasts, mediates hepatic acute phase response); long half-life; side effects include injection site rxn, increase susceptibility to infection, alterations in lipid profile (increases cholesterol and triglycerides)
93
gout
arthritis stemming from a metabolic disorder resulting in elevation of uric acid and inflammatory microcrystals in the joint; more common in women post-menopause; more common in obese individuals; polyarticular gout often affects the PIP and DIP joints; pathology characterized by neutrophils in the synovium/synovial fluid, NSU crystals in cytoplasm of neutrophils
94
tophaceous gout
repetitive episodes of gout leading to significant tophus deposits on articular surfaces that destroy cartilage; punched-out lesions and overhanging edges of joints visible on X-ray
95
osteomyelitis
bone infection; sometimes visible on imaging as a region of lucency, but X-rays tend not to be very sensitive (better to use bone scan or MRI); generally does not cause fever; Tx requires long courses of Abx, surgery (removal of sequestra and/or prostheses); bone must be covered by tissue for treatment to be effective
96
prosthetic joint infection
osteomyelitis resulting from infection of prosthetic material implanted in bone with spread of organisms into adjacent bone; more common in adults; commonly caused by coagulase (-) Staph spp. (like to stick to foreign materials), S. aureus, gram (-), Strep spp.
97
hematogenous osteomyelitis
bone infection resulting from seeding of bone related to a previous bacteremia; more common in children; may be caused by S. aureus, Strep spp., gram (-), Mycobacterium tuberculosis, Salmonella spp. (in sickle-cell pts)
98
direct implantation osteomyelitis
bone infection resulting from a penetrating injury; commonly caused by Pseudomonas when precipitated by injury through a shoe, as Pseudomonas likes to grow in damp areas (such as shoes)
99
contiguous osteomyelitis
bone infection resulting from direct spread of bacteria from an overlying wound or pressure ulcer that is deep with thick exudate; more common in adults; may be related to a diabetic foot ulcer; commonly caused by S. aureus, gram (-), Strep spp., anaerobes, Candida spp.
100
sequestrum
piece of dead bone resulting from osteomyelitis-related damage to periosteum; may get trapped and behave like a foreign body; requires surgical removal
101
involucrum
external bone formation as a reaction to osteomyelitis
102
Brodie's abscess
bone abscess that develops locally due to osteomyelitis
103
biofilm
aggregation of microorganisms adherent to a surface, esp. hard surfaces; embedded within a matrix (slime, extracellular polymeric substance, glycocalyx); changes organisms' biochemistry and physiology (compared to planktonic organisms), more likely to be resistant to Abx
104
rifampin
antibiotic that is more effective for treating biofilm organisms
105
vancomycin
antibiotic used for treatment of MRSA
106
acetaminophen
analgesic drug used in the treatment of osteoarthritis; effect size is small, but the drug is safe
107
tofacitinib
drug used in the treatment of RA in pts who have had inadequate response/intolerance to methotrexate; inhibits Janus kinase enzymes; absorbed orally; side effects include increased susceptibility to infection, alterations in lipid profile (increases cholesterol and triglycerides)
108
anakinra
recombinant protein used in the treatment of adult RA in pts who have had inadequate response to one or more DMARD; competitive antagonist of IL-1R; short half-life (requires daily SQ administration); may be used alone or in combination with other DMARDs, but NOT with TNF-alpha antagonists
109
duloxetine
SNRI approved for treatment of chronic musculoskeletal pain; used in the treatment of osteoarthritis; targets descending inhibitory pain pathways - imbalance of 5-HT and NE has been implicated in chronic pain associated with central sensitization (analgesic effect occurs sooner than the anti-depressant effect and at a lower dose); side effects include nausea, dry mouth, and constipation
110
methotrexate
immunosuppressive drug used in the treatment of RA; inhibits de novo purine synthesis
111
hyaluronic acid
used for treatment of OA of the knee as joint injection (daily for 3 weeks); polysaccharide composed of glucosamine and glucuronic acid, inhibits inflammatory mediators, decreases cartilage degradation, and promotes cartilage matrix synthesis; side effects include joint inflammation and risk of infection; only used in pts who cannot take NSAIDs or who do not respond to them
112
leflunomide
DMARD used in the treatment of RA; inhibits proliferation and activity of T cells and B cells
113
ibuprofen
NSAID (propionic acid derivative)
114
naproxen
NSAID (propionic acid derivative) used for treatment of gout
115
indomethacin
NSAID (acetic acid derivative) used for treatment of gout
116
celecoxib
NSAID (diaryl heterocyclic compound) used for the treatment of gout
117
aspirin
NSAID (salicylic acid derivative); covalently modifies COX-1 and COX-2, irreversibly inhibits activity; metabolized to salicylate by esterases, esp. in liver; salicylate renal excretion increases when metabolic pathways get saturated; NOT used in treatment of gout, as it blocks uric acid excretion at low doses (may be uricosuric at large doses)
118
capsaicin
topical treatment for osteoarthritis; exogenous agonist for TRPV1 receptor, induces release of substance P ultimately depleting neuron stores of substance P/prevents reaccumulation; side effects include transient application site reactions (pain and erythema)
119
chronic papillary synovitis
chronic inflammation of the synovium characterized by CD4+ T-cells, plasma cells, macrophages, and giant cells; generally accompanied by synovial cell hyperplasia that creates a papillary pattern on the surface of the synovium with finger-like projections
120
rheumatoid nodules
subcutaneous nodules associated with RA that develop in areas of minor trauma/rubbing and those exposed to pressure due to vascular damage; non-tender, firm, round/oval; possess central zone of fibrinoid non-caseating necrosis surrounded epithelioid histiocytes, lymphocytes, and plasma cells
121
glucocorticoid
class of anti-inflammatory drugs sometimes used for treatment of RA; suppresses the induced expression of COX-2, inhibits the action of phospholipase A2; blocks cytokine release (IL-1, IL-2, IL-3, IL-6, IL-8, IL-12, TNF-alpha, GM-CSF, IFN-gamma); inhibits IgE-dependent histamine/leukotriene release
122
glucosamine
symptomatic slow-acting drug for OA (SYSADOA); aminosaccharide, principle substrate of proteoglycan biosynthesis, contributes to maintenance of cartilage integrity
123
chondroitin
symptomatic slow-acting drug for OA (SYSADOA); glycosaminoglycan, maintains viscosity in joints, stimulates cartilage repair mechanisms, and inhibits enzymes that break down cartilage
124
pannus
synovial proliferation associated with RA that extends over the articular surface and fills the joint space; behaves like a benign, locally-invasive tumor; over time, destroys articular cartilage and increases osteoclast activity in underlying bone; may cause joint fusion/fibrosis/ossification
125
eburnation
complication of advanced osteoarthritis; absence of articular cartilage on bone surface, exposed bone appears polished
126
monoarthritis
joint pain affecting only one joint
127
polyarthritis
joint pain affecting greater than five joints
128
monosodium urate
uric acid metabolize that crystalizes and deposits in joints and other loci throughout the body in gout; birefringent
129
tophi
MSU crystal aggregates/deposits throughout the body; generally surrounded by lymphocytes, giant cells, and fibroblasts; common in joints and on the helix of the ear
130
subchondral cyst
AKA geodes; areas of periarticular bone matrix degradation characteristic of advanced osteoarthritis; formed by a break in cartilage that allows synovial fluid to enter subchondral space, forms fibrous-walled cyst
131
osteophyte
complication of osteoarthritis; bony outgrowth that develops at margins of articular surfaces in characteristic locations for specific joints; results in increased joint size
132
Heberden nodes
osteophytes that form on DIP joints in late stage osteoarthritis; paired, seem to reveal phalangeal epicondyles
133
Bouchard nodes
osteophytes that form on PIP joints in late stage osteoarthritis; joints appear swollen/depressed
134
soft tissue tumors
nonepithelial extraskeletal tumors, excluding reticuloendothelial system, glia, and supporting tissue of parenchymal organs
135
determinants of tumor grade
degree of differentiation/pleomorphism, average number of mitoses, extent of necrosis
136
lipoma
benign soft tissue tumor originating in adipocytes; most common soft tissue tumor of adulthood; conventional lipomas most common, soft, yellow, well-encapsulated, may possess 12q14-q15 aberrations
137
liposarcoma
one of the most common sarcomas of adulthood (40-60 y.o); common in deep soft tissues of proximal extremities and retroperitoneum; pleomorphic variant is aggressive and may metastasize; well-differentiated LPS may possess supernumerary ring chromosomes (amplification of 12q14-q15, containing MDM2); myxoid/round LPS may possess t(12;16), forms FUS-CHOP fusion gene
138
lipoblast
regenerative adipocyte; distinguishable histologically based on presence of multiple, smaller fat vacuoles with a more centrally-located nucleus
139
lipoblastoma
tumor composed of lipoblasts, most common in children, may possess PLAG1 mutation
140
deep-seated fibromatosis (Desmoid tumor)
fibrous tumor with behavior between benign and low-grade fibrosarcoma; most common in young adulthood; frequently recurs after excision; some associated with Gardner syndrome or mutations in APC/beta-catenin genes
141
fibrosarcoma
malignant tumors composed of fibroblasts; most common in adults in deep tissues of the thigh, knee, and retroperitoneum; generally aggressive; cells are difficult to stain, all markers but vimentin are negative (intermediate filament present in every mesenchyme-derived cell)
142
rhabdomyosarcoma
most common soft tissue sarcoma of childhood and adolescence; most common in head and neck or genitourinary tract; may be embryonal, alveolar, or pleomorphic
143
embryonal rhabdomyosarcoma
most common subtype of rhabdomyosarcoma; made up of cells that recapitulate rhabdomyoblasts; often has loss of 11p15 and extra copies of 8, 12, 13, and/or 20; botryoid subtype commonly presents in infant girls as protuberant vaginal lesions (polypoid, gelatinous mass with bunch-of-grapes appearance)
144
alveolar rhabdomyosarcom
second-most common subtype of rhabdomyosarcoma; most frequent in adolescence/yound adulthood in deep soft tissues of the extremities; has pathognomonic translocation - t(2;13)/PAX3-FKHR or t(1;13)/PAX7-FKHR
145
synovial sarcoma
malignant tumor of unknown histogenesis; 5-10% of all soft tissue sarcomas; most common in young adult males; most occur in deep soft tissue of extremities, especially around the knee; biphasic or monophasic (spindle-shaped cells and/or glandular cells); generally possesses t(X;18) with SYT-SSX1 or SYT-SSX2, diagnosed via cytogenetics; poor prognosis
146
psudosarcomatous proliferations
reactive, non-neoplastic lesions that develop in response to some form of local trauma or are idiopathic; develop suddenly and grow rapidly; possess hypercellularity, mitotic activity, and primitive (histologically mimics sarcoma); examples include nodular fasciitis, myositis ossificans
147
synovitis
thickening of synovium around joints; tender and squishy with firm palpation
148
rheumatoid arthritis
inflammatory symmetric chronic polyarthritis affecting large and small joints; both T cell and B cell involvement; associated with genetic predisposition (HLA-DR), females, and smoking; characterized by proliferation of synovium appearing as a benign, locally-invasive tumor, joint space narrowing, periarticular osteopenia; presents with symmetrical, gradual onset, prolonged morning stiffness, swan neck deformity, boutiniere deformity, nodules, vasculitis
149
osteoarthritis
non-inflammatory arthritis characterized by gradual loss of cartilage and development of bony spurs/subchondral cysts at the margins of joints; caused by imbalance in cytokine and growth factor activity; most common in older women, associated with genetics, obesity/diabetes, and trauma; presents with brief morning stiffness with pain that is worse at the end of the day or during use/exercise; tends to target hands and large weight-bearing joints (i.e. hips and knees); imaging may reveal subchondral sclerosis, geodes, and osteophytes
150
fractures
breaks in bone; due to anisotropic toughness of bone, transverse cracks are less able to propagate than longitudinal cracks; due to lamellar structure of bone and ability of cement lines between lamellae/osteons to absorb and dissipate force
151
rickets
abnormal bone modeling in a growing individual leading to long bones possessing a bowed shape; due to osteomalacia during development; pseudofractures are pathognomonic
152
sclerosteosis
disease in which skeletal mass is abnormally high due to mutations in SOST, such that bones perceive that they are being loaded even when they are not (osteocyte disease)
153
osteomalacia
disease resulting from inadequate mineralization of bone matrix; may be due to malabsorptive disorders (i.e. celiac disease), vitamin D deficiency/resistance, phosphate wasting disorders, or calcium deficiency; when it occurs in a growing individual, causes rickets; bone cells function normally, but lack the appropriate mineral substrates
154
osteoid osteoma
benign bone tumor, generally located at the metaphysis/diaphysis of long bones (esp. femur and tibia, around the knee); on imaging shows radiolucent lesion with sclerotic cortex; on histology, shows formation of disorganized/immature bone with no nuclear atypia and well-defined borders; classically presents as severe pain that is worse at night and relieved by aspirin
155
osteoblastoma
benign bone tumor, generally located in vertebrae or at the metaphysis of long bones; on imaging shows large, expansile radio-lucency with mottling; on histology shows formation of disorganized/immature bone with no nuclear atypia and irregular borders; presents as pain that does not respond to aspirin
156
osteochondroma
most common benign bone tumor, generally located at the metaphysis of long bones; juxtacortical, bony outgrowth from bone surface complete with marrow and cartilage cap; malignant transformation is rare, but more common in hereditary multiple exostoses (autosomal dominant: EXT-1 [8q24] mutation)
157
chondroblastoma
bone tumor, generally located at the epiphysis
158
Ewing sarcoma
AKA PNET, peripheral neuro-ectodermal tumor; second-most malignant bone tumor in childhood (third-most common overall), generally located at the diaphysis of long tubular bones, ribs, and pelvis; commonly presents in adolescents and young adults as painful, enlarging mass; imaging shows destructive, moth-eaten, permeative medullary lesion with soft tissue mass and "onion-skin" pattern of periosteal growth; histology shows primitive small round blue cells with neural phenotype, positive for membranous CD99, and abundant glycogen; hemorrhage and necrosis common; EWS gene usually involved, often t(11;22) (FLI-1-EWS fusion)
159
giant cell tumor
benign, locally-aggressive bone tumor, generally located at the epiphysis of bones, esp. knee, proximal humerus, and radius; may destroy cortex of bone and extend into soft tissue; histology shows multiple, multi-nucleated giant cells
160
non-ossifying fibroma
most common space-occupying lesion of bone, common developmental cortical effect; most commonly found at metaphysis of tibia and femur; imaging shows eccentric, lytic, peripheral sclerosis; histology shows "starry night" cells, may have a few giant cells; generally an incidental finding or associated with pathologic fracture
161
fibrous dysplasia
developmental arrest of bone; monostotic lesions most commonly seen in adolescents in the ribs, mandible, and femur; polystotic lesions most commonly seen in infancy/childhood, cause crippling deformities and/or craniofacial involvement; imaging shows expansile, circumscribed lesion with thinned cortex and smooth "ground glass" appearance (may be multiple lesions); histology shows curvilinear "Chinese character" woven bone surrounded by fibroblastic stroma (no significant osteoblastic rimming)
162
multiple myeloma
most common in pts >40 y.o.; dx. via PEPE/UPEP/serum free light chains; histology shows CD138+
163
lymphoma of bone
generally presents as multiple lesions; histology shows CD20+ (B-cell lymphoma)
164
unicameral bone cyst
on CT scan may show air/tissue/fluid level
165
aneurysmal bone cyst
expansile cyst in the bone
166
osteosarcoma
malignant mesenchymal matrix-forming bone tumor; generally found at the metaphysis of long bones, though may be found in flat bones and spine in older pts; bimodal age distribution; fast-growing, not often caught early, lung metastases are common; associated with hereditary Rb, Li-Fraumeni syndrome, overexpression of MDM2, INK4, and p16, and sites of bone growth/disease (as in Paget's disease); imaging shows poorly-defined lesion with bone/cortical disruption, matrix deposition, soft tissue extension, and Codman's triangle (formation of periosteum around tumor); histology shows irregular cells, diffuse chromatin, multiple/atypical mitoses; tx includes chemotherapy and surgical resection (in that order)
167
desmoid firbomatosis
adult benign soft tissue tumor; rarely metastasizes, but very locally aggressive; imaging shows tumor that stays dark on T2 MRI (most tumors light up); histology shows beta-catenin+ cells; tx includes radiation and surgical resection
168
soft tissue sarcoma
can be differentiated from a lipoma with a T2-weighted MRI (T2 is fat-suppressing)
169
enchondroma
benign hyaline cartilage tumor, generally found in the medulla of the diaphysis of bones in the appendicular skeleton (small bones of hands and feet); usually asymptomatic incidental finding; imaging shows lytic, lobulated lesion with cortical thinning; histology shows lobules of hyaline cartilage with minimal atypia and sparse cellularity; usually requires no treatment
170
chondrosarcoma
malignant tumor that produces a purely cartilaginous matrix; second-most common bone sarcoma, primarily affects older adults; generally found in the medulla of the metaphysis/diaphysis of long bones and in the pelvis and ribs; often present calcifications that may be lost in grade 3 tumors, along with cortical erosion and occasional soft tissue extension; imaging shows popcorn-like, moth-eaten appearance; histology shows highly cellular tissue with pleomorphic nuclei, frequent binucleation; dedifferentiated tumors possess no real cartilage; grade 3 may metastasize to lungs
171
lipoma
benign soft tissue tumor originating in adipocytes; to be definitively diagnostic of lipoma, tumor must appear as fat on all MRI views; tumor generally has a membrane around it
172
Ollier's disease
genetic syndrome that causes appearance of multiple enchondromata that tend to have a regional distribution; may or may not be accompanied by severe skeletal malformation; point mutations in IDH1 or IDH2
173
Maffucci's syndrome
genetic syndrome that causes appearance of multiple enchondromata and angiomata with severe skeletal malformation and higher incidence of malignant transformation; point mutations in IDH1 or IDH2
174
periosteal chondroma
benign hyaline cartilage tumor found in bones juxtacortically (i.e., located cortical surface under the periosteum)
175
McCune-Albright syndrome
genetic syndrome characterized by polyostotic fibrous dysplasia, endocrinopathies, and cafe-au-lait spots; symptoms include sexual precocity, acromegaly, and Cushing's syndrome; caused by activating germline mutations of GNAS, which causes excess cAMP/endocrine gland hyperfunction
176
bone modeling
change in bone radial size and/or shape due to osteoclast and osteoblast activity; primary stimuli include strain (whole bone level) and shear stress (cellular level); modulated by Wnt/beta-catinin signaling, which stimulates osteoblast proliferation and matrix synthesis; when osteocytes are unloaded, they produce SOST, which inhibits Wnt
177
scleratome
cells from the ventral part of a somite that are influenced by Shh and noggin; become precursors for bone, cartilage, tendon, endothelium, and meninges; contribute to the skeletal tissue forming mesenchyme of the trunk; during vertebral development the central compartment contributes to the pedicle and proximal ribs, ventral compartment to the vertebral body and intervertebral discs, dorsal to the dorsal part of neural arch and spinous process, and lateral to the distal rib; cells in medial part form meninges and blood vessels of the spinal cord; also contributes to rib formation
178
somatic mesoderm
population of cells derived from the lateral mesoderm that contributes to skeletal forming mesenchyme in the trunk; includes precursors of sternal primordial
179
paraxial mesoderm
mesoderm cells located next to/surrounding the notochord; precursor for all skeletal muscle
180
ossification center
areas in bone primordial in which the ossification process begins; appear in both intramembranous and endochondral ossification
181
bone age
the amount of epiphyseal cartilage retained within the skeleton
182
somite
segment of paraxial mesoderm that possesses lots of cells with a variety of developmental fates, including cartilage, bone, skeletal muscle, and fibrous connective tissue; individual cellular specification depends on the location of the cell within the somite and the extrinsic signals; one of those fates is skeletal muscle of the trunk and limbs
183
dermamyotome
cells from the dorsal part of a somite that are under the influence of Wnt signaling from the neural tube and surface ectoderm and maintain their epithelial structure; ultimately form myogenic cells and skin dermis
184
somitocoel
central cavity of a somite around which epithelium-type cells arrange; becomes part of the sclerotome; ultimately contributes to vertebral joints, intervertebral discs, and proximal ribs
185
centrum
ventral part of primitive vertebrae that ultimately develops into the vertebral body
186
neural arch
dorsal projections of primitive vertebrae
187
neurocentral junction
synchondrosis; cartilage plate that remains between the base of the neural arch and centrum of primitive vertebrae; allows growth of the vertebrae; ossifies prior to age 10
188
costal and transverse processes
lateral projections of primitive vertebrae
189
sternabrae
secondary segmentation of sternal primordium that occurs after fusion of cartilage bars; later refusing forms the body of the sternum, while the cranial-most sternebra remains unfused and becomes the manubrium
190
resegmentation
process by which the loosely-arranged, cranial half of one somite merges with the tightly-packed, caudal half of the adjacent somite; leads to intersegmental vertebral development; allows skeletal muscles derived from dermomyotomes to span adjacent vertebrae, intersegmental arteries to pass across the bodies of vertebrae, and spinal nerves to reside near intervertebral discs
191
occipital somites
lead to formation of occipital myotomes, which contribute to muscles in the head and neck (along with head mesoderm)
192
myotome
population of myogenic cells that originate from the dorsomedial and dorsolateral edges of the dermamyotome that undergo epithelium to mesenchyme transformation (skeletal muscles of trunk and limbs); also contains a small population from the central portion of the dermamyotome (satellite cells); once cells become part of myotome, developmental potency is limited to skeletal muscle
193
myoblast
post-mitotic myogenic cells that are committed muscle cells; myogenic regulatory factors induce differentiation and actin and myosin synthesis; secrete fibronectin once they have reached their definitive location in the embryo
194
multinucleated myotube
fused chains of myoblasts that begin to form once myoblasts reach their final location within the embryo; requires M-cadherin
195
satellite cell
myogenic stem cells that lie between the muscle fibers and the basement membrane and mediate postnatal growth of skeletal muscle; originate from the central portion of the dermamyotome, then undergo epithelial to mesenchyme transformation (after abaxial and primaxial domain cells); formation is mediated by Pax3 and Pax7
196
myogenic cell
pre-myoblasts; precursor cells for muscles found in the myotome; differentiate from the mermamyotome based on Bmp4 (lateral mesoderm), Wnt, and Ssh (neural tube and notochord) signaling; some originate in the medial and lateral edges of the dermamyotome (precursors for skeletal muscle of trunk and limbs); others originate in the central portion of the dermamyotome (precursors for satellite cells)
197
abaxial domain
cells originating from the ventrolateral portion of the dermamyotome that migrate across the LSF into somatic mesoderm, express MyoD, and form muscles of the abdominal wall, limbs, and infrahyoid
198
primaxial domain
cells originating from the dorsomedial portion of the dermamyotome that remain adjacent to the neural tube/notochord, express Myf5 and MyoD, and form intrinsic muscles of the back and prevertebral and intercostal muscles
199
epaxial
muscles that are innervated by dorsal primary rami of spinal nerves; includes intrinsic muscles of the back
200
hypaxial
muscles that are innervated by ventral primary rami of spinal nerves; includes ventrolateral body wall and limb muscles
201
cranial nerve
innervates muscles in the head and neck that originate from head mesoderm and occipital myotomes
202
spinal nerve
innervates muscles in the trunk ad limbs that originate from the ventrolateral and ventromedial edges of the myotome
203
lateral somite frontier
border of cells between the lateral edge of the somite and the medial edge of the lateral mesoderm; result of the interaction of different signaling molecules from somites, lateral mesoderm, and surrounding tissues; defines two microenvironments within which dermamyotome-derived myogenic cells may develop/differentiate
204
limb bud and field
limb field is an area of somatic mesoderm located on each side of the embryo at specific axial levels; limb bud is an elevation of somatic mesoderm that forms as cells begin to produce Fgf-10, with core somatic mesoderm covered by a jacket of surface ectoderm
205
apical ectodermal ridge
a thickened ridge of cells that runs from anterior to posterior along the interface between dorsal and ventral surfaces of the limb bud; induced by production of Fgf-10 by mesenchyme cells
206
preaxial
cranial border of the limb along the anterior-posterior axis
207
postaxial
caudal border of the limb along the anterior-posterior axis
208
zone of polarizing activity
a group of somatic mesoderm-derived mesenchymal cells along the posterior border of the limb; secretes Shh to influence patterning along the anterior-posterior axis of the limb (can be mimicked by retinoic acid)
209
talas bone
bone in the ankle; defects cause clubfoot
210
hypothyroidism
causes cretinism/pituitary dwarfism; symptoms include skeletal and ear anomalies, mental retardation, and younger bone age
211
achondroplasia
autosomal dominant condition characterized by dwarfism; caused by interference with epiphyseal plate development due to a mutation of FGFR-3; particularly affects the proximal segment of limbs; affected individuals have a normal-sized trunk, disproportionately shortened limbs, small/immature mid face, short fingers, and accentuated lordosis
212
osteogenesis imperfecta
genetic mutation in expression of type I collagen; may be dominant or spontaneous; characterized by fragile skeleton, blue sclera, and other defects in ears, joints, spine, and teeth
213
mucopolysaccharide disorders
family of metabolic diseases that are autosomal recessive; caused by absence/defect in an enzyme that leads to accumulation of GAGs in tissues and cells; causes dwarfism, bone irregularities, chronic/progressive distortions of face and skull, thickened/hairy skin, organ enlargement, and altered mental development
214
dysraphism
failure of fusion of the neural arches of a vertebra
215
spina bifida
series of conditions where one or a few adjacent vertebrae have unfused spinous processes; mildest form is spina bifida occulta, which is usually asymptomatic
216
scoliosis
abnormal lateral curvature of the spine; congenital may be caused by malformed vertebrae, idiopathic forms are not
217
kyphosis
exaggeration of flexion curvature of the spine; may be congenital due to vertebral malformation or acquired
218
lordosis
exaggeration of extension curvature of the spine; may be congenital due to vertebral malformation or acquired
219
Klippel-Feil sequence
AKA brevicollis; recessive disorder characterized by the presence of several fused cervical vertebrae; symptoms include shortened neck, low nuchal hair line, limited cervical spine mobility, genitourinary and cardiopulmonary defects, and hearing loss; may have undescended scapula, cervical rib, or scoliosis
220
pectus excavatum
posterior depression of the sternum; may press the heart against the spine, may require surgery to correct
221
cervical rib
accessory rib that may cause problems if it compresses the brachial plexus
222
congenital torticollis
fixed rotation and tilting of the head to one side; more common on the right side; commonly co-morbid with hip dysplasia; may be caused by defect with SCM muscle or insufficient space for fetus in uterus; may also occur in older children secondary to infections or trauma to the SCM muscle
223
prune belly syndrome
syndrome characterized by absence of abdominal muscles, undescended testicles, and bladder/urinary tract abnormalities; may be due to prenatal accumulation of fluid in the lower abdomen due to urinary system anomalies; occurs almost exclusively in males
224
Poland sequence
absence of the pectoralis major muscle (usually sternocostal head) and pectoralis minor muscle; causes ipsilateral nipple to be displaced or missing, ipsilateral breast tissue to be hypo plastic or missing, and deficiency of subcutaneous fat/axillary hair; rib cage may also be hypoplastic; more common on right side and in males
225
amelia
birth defect in which an entire limb is missing
226
meromelia
birth defect in which part of a limb is missing; may be transverse type, in which there is truncation/amputation somewhere along the proximal-distal axis of the limb, or longitudinal type, in which certain parts may be missing along the anterior-posterior axis
227
phocomelia
birth defect in which the distal segment of a limb is attached to a more proximal segment with the intervening segment missing; distal segment may be attached directly to the girdle; common in children born to mothers who had taken Thaladomide during pregnancy
228
oligodactyly
a form of longitudinal-type meromelia in which there is an absence of the median portion of the distal limb segment, causing a lobster claw deformity; may affect the hand or foot
229
syndactyly
complete or partial fusion of one or more digits; may be due to failure of interdigital apoptosis; opposite condition is sirenomelia, the result of fused limb fields
230
polydactyly
duplication of digits; may be inherited via autosomal dominant or recessive pattern, usually bilateral
231
brachydactyly
undergrowth/shortening of a digit due to lack of certain joints
232
clubfoot
foot-ankle defect involving the talas bone; most common form is talipes equinovarus, in which the foot is plantar-flexed, inverted, and adducted due to displacement of the navicular, calcaneus, and cuboid bones around the talus; more common in boys
233
Sprengel deformity
undescended, dysplastic scapula located at C4-T2 (should be at T2-T7); usually on left side, but may be bilateral; causes limited shoulder movement and disfigurement; most common in males; may be co-morbid with vertebral anomalies, absent/fused ribs, Klipple-Feil sequence, or scoliosis
234
developmental dysplasia of the hip
condition in which the hip joint is easily dislocated due to underdevelopment of the femoral head and/or the hip socket; often accompanied by general joint laxity and breech births; may be caused in part by maternal hormones that soften connective tissue and abnormal position of the child in the uterus; may also be a hereditary component; when unilateral, it is more common on the left side
235
cleidocranial dysplasia
hypoplasia or aplasia of the clavicles; usually bilateral and accompanied by other anomalies, including large head, small face, long neck, drooping shoulders, short/narrow chest, delayed fontanelle closure, incomplete pubic development, short fingers, and dental problems; autosomal dominant or spontaneous; caused by defects in Runx-2 gene
236
Fgf/Fgf receptor
family of signaling molecules that influences limb development; Fgf-10 from the somatic mesoderm induces AER formation; Fgf-8, -4, and -2 are produced by the AER and maintain Fgf-10 production, which promotes mesenchyme cell proliferation while inhibiting cell differentiation
237
Wnt
developmental signal from the neural tube, notochord, and surface ectoderm that induces dermamyotome formation, epithelium to mesenchyme transformation of dorsomedial DM cells, and Lmx-1 expression of dorsal mesenchyme during limb development
238
noggin
a Bmp inhibitor originating from the neural tube that modulates the Bmp4 gradient across the dermamyotome; influences sclerotome development
239
Pax 1, 2, 7, 9
Pax 1 and 9 are expressed by ventral somite cells and induce them to transform into mesenchyme/form the sclerotome; Pax7 induces satellite cell formation from myogenic cells of the central dermamyotome
240
Shh
developmental signal from the neural tube and notochord that induces epithelium to mesenchyme transformation of dorsomedial DM cells; influences sclerotome development; secreted by the zone of polarizing activity to influence patterning along the anterior-posterior axis by inducing asymmetric, nested expression of Hox genes
241
Hox
signal that mediates regionalization of the spine via nested expression along the cranial-caudal axis; determines the type and location of vertebrae formation; mediated by retinoic acid; null mutations cause cranialization, gain-of-function mutations cause caudalization; also contributes to axial positioning of limb fields and patterning for digit location
242
Retinoic acid
mediates Hox signaling; can also mimic Shh signaling in the zone of polarizing activity
243
myogenic regulatory factors
transcription factors that regulates development of muscle-forming mesenchyme; includes MyoD, Myf5, Myf4, myogenenin, and Mef2
244
Pitx-1
transcription factor expressed in the lower limb
245
Lmx-1
factor expressed in dorsal mesenchyme; induced by Wnt and radical fringe signaling from the dorsal ectoderm; contributes to dorsal-ventral patterning of the limbs
246
Engrailed-1
factor expressed by ventral ectoderm that prevents Lmx-1 expression in the ventral mesenchyme; contributes to dorsal-ventral patterning of the limbs
247
radical fringe
factor expressed in the dorsal ectoderm; induces Lmx-1 expression in the dorsal mesenchyme; contributes to dorsal-ventral patterning of the limbs
248
Tbx 4, 5
Tbx 4 is a transcription factor expressed in the lower limb; Tbx 5 is a transcription factor expressed in the upper limb
249
Sox9
transcription factor expressed by STFM destined to become cartilage and by mature cartilage
250
RunX2
AKA Cbfa-1; transcription factor expressed by STFM destined to become bone
251
recommended dietary allowance (RDA)
the average daily dietary nutrient intake level that is sufficient to meet the nutrient requirement for nearly all healthy individuals in a particular life stage and gender group
252
tolerable upper limit (UL)
the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population
253
adequate intake (AI)
the recommended average daily intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group of apparently healthy people that are assumed to be adequate; used when RDA cannot be determined
254
estimated average requirement (EAR)
the average daily nutrient intake level that is estimated to meet the requirements of half of the healthy individuals in a particular life stage and gender group
255
dietary reference intakes (DRI)
a group of nutrient-based reference values that are used to assess and plan the diets of healthy people; includes RDA, UL, AI, and EAR
256
calciferol
AKA vitamin D; two forms, ergocalciferol (VD2) and cholecalciferol (VD3); cholecalciferol is form made by mammals from cholesterol, has 100% activity; preferred supplementation form; ergocalciferol has 100% activity but is less stable than D3, may be less effective; VD3 can be found as calcitriol
257
international unit (IU)
unit of measure for a substance, allows for easier comparison across substances
258
sprain
ligament injury
259
strain
muscle injury
