Chapter 25- Bones, Joints Flashcards
What is the meaning of osteoporosis
Porous, or thinned out bone
What is the meaning of osteomalacia
Weakened, soft bone
What is the meaning of Osteopetrosis
Peter=rock, stone bone
What is the meaning of osteogenesis imperfecta
Imperfect origin of bone
Osteitis deformans
Deforming bone-itis
What is the meaning of osteodystrophy
Difficult/bad growing bone
The hardness of the bone is made up of which material
Hydroxyapatite
What is contained in bone hydroxyapatite
99% of body calcium
85% if phosphorous
What is the source and function of osteopontin
Osteoblasts and functions in calcium homeostasis
What are the characteristics of woven bone and which individuals are commonly seen to have it
- Produced rapidly during fetal development, abnormal in adults
- Seen in fracture repair
- Arrangement of collagen, with less structural integrity
What is the structure of woven versus lamellar bone
Woven bone has more collagen and disorganized
Lamellar bone: parallel collagen and stronger
Which cells in the bone regulate the calcium and phosphate levels
Osteocytes
What is the method of bone development in long bones
Endochondral ossification
*New bone at the bottom of the growth plate giving longitudinal growth
What is the method of bone growth in flat bones
Intramembranous ossification
*new bone placed on preexisting surface, aka appositional growth
When is peak bone mass achieved
Early adulthood after cessation of skeletal growth
Rank and RANKL result in which process with regards to bone
Breakdown
OPG results in which process with regards to bone
Buildup
What is is the pathway/receptor activation involved with RANK
NF kappaB
What is the mechanism that OPG works
Binds to the RANKL and prevents it from binding to the RANK
What is the process and result of WNT proteins with regards to bones
WNT proteins bind to LRP5/6 on osteoblasts and activate Betacatenin and production of OPG
*Results in bone building
What is the process and result of the activation of sclerostin
Inhibits the WNT/Beta catenin pathway, Inhibition in the production of OPG
*Results in bone breakdown
What are the compounds that commonly cause the building of bone
Testosterone
Estrogen
Vitamin D
What are the common compounds that cause bone breakdown
PTH
IL-1
Glucocorticoids
What is the role of M-CSF
On osteoclasts and stimulate tyrosine kinase cascade that causes the generation of osteoclasts
What is dystosis of bone
Migration and condensation of mesenchyme into cartilage analage
What is the dysplasia of the bone
GLobal disorganization of bone and cartilage
What are the genes that can cause dystosis
Homeobox genes
What are the common conditions that are classified under dystosis
Aplasia (missing bone)
Supernumerary (extra bone)
Syndatcyly or craniosynostosis (abnormal fusion of bone)
What is the gene associated with:
-Short terminal phalanges of thumb and big toe
HOXD13
What is the gene associated with:
- Abnormal clavicle
- Wormian bones (extra cranial sutures)
- supernumerary teeth
RUNX2
What is the gene associated with:
Achondroplasia, aka causing drawfism
FGFR3 gain of function
What are the clinal features of drawfism
Normal trunk length
No change in the longevity, intelligence, or reproductive status
What is the gene associated with:
Thanatrophic dysplasia
Most lethal form of drawfism
FGF3
What are the clinical features of thanatophoric dysplasia
- Small chest cavity (insufficient respiration)
- microcephalic
What is the gene associated with:
Abnormal bone density
- LPR5 receptor (osteoporosis or osteopetrosis)
- Mutations in RANKL (decreased or missing osteoclasts)
What is the structure affected by osteogenesis imperfecta
Type 1 collagen (alpha 1 and 2 chains)
What is the state and type of collagen effect in type 1 osteogenesis imperfecta
Decreased amount of type 1 collagen, but the structure is normal
When do most fractures in type 1 osteogenesis imperfecta occur
Before puberty, with the decreased frequency as the age increases
What is the lifespan with type 1 osteogenesis imperfecta
Normal life span with normal or near normal stature
What are the clinical features of osteogenesis imperfecta type 1
- *Blue/purple/grey tint to sclera
- Triangular face
- brittle teeth
- Hearing loss (in the 20s/30s)
What is the state of the bone deformities in type 1 osteogenesis imperfecta
Normal bone with minimal to absent deformities
What is the lifespan in type 2 osteogenesis imperfecta
Lethal
What are the clinical features of type 2 osteogenesis Imperfecta
- Lethal due to respiratory issues arising from the small thoracic cavity
- Numerous fractures and severe bone deformities
- Small stature with small lungs
What is the state of bone deformity in type 3 osteogenesis imperfecta
Bone deformity, usually severe
What is the state and type of cartilage in type 3 osteogenesis imperfecta
Collagen type 1 in improperly formed
What are the clinical features of type 3 osteogenesis imperfecta
- *Fractures present at birth, usually revealing healed fractures
- Blue sclera
What is the status and type of collagen in type 4 osteogenesis imperfecta
Collagen type 1 is improperly formed
What are the clinical features of osteogenesis imperfecta type 4
- Inbetween type 1 and 3
- White or near white sclera
- shorter than normal stature
- Fractures before puberty
What is the description of osteopetrosis
Aka Marble bone disease or Albee’s-Schoenberg disease
What is the gene and its product mutation in osteopetrosis
CLCN7, which encodes the proton pump carbonic anhydrase 2 on osteoclasts and renal tubular cells
*carbonic anhydrase required for proton generation from CO2 and water
What is the result of carbonic anhydrase deficiency in osteopetrosis
Inability to acidity the osteoclast reabsorption pit to solubilize hydroxyapitie, results in lack or resorption
What are the physical findings in osteopetrosis
Lack a medullary cavity, with bulbous ends of long bones (which look like Erlenmeyer flasks)
-Neuronal foramina are small, which can compress the nerves
What is the inheritance fo the severe infantile type of osteopetrosis
Autosomal recessive
What is the inheritance form of the mild type of osteopetrosis
Autosomal dominant
What are the clinical findings in those patients with the severe infantile form of osteopetrosis
- Cranial nerve defects (optic atrophy, deafness, facial paralysis)
- Fractures, anemia, hydrocephaly
What are the clinical findings of the mild from of osteopetrosis
Repeated fractures
-Mild cranial nerve defects and anemia
What is the cause of mucopolysaccharidosis
Lysosomal storage disease in which there is a deficiency in the enzyme that degrades dermatan sulfate, heparan sulfate and heratan sulfate
What is the enzyme that is commonly affected in mucopolysaccharidoses
Acid hydrolase enzymes
What is the result of mucopolysaccaridoses
Mucopolysaccharides accumulate in the chondrocytes and in the extracellular space, which results in the death of the cells and defects in the articular cartilage
What are the physical features of a patient with mucopolysaccaridoses
Short stature, chest wall abnormalities, and malformed bones
What are the three only causes of primary osteoporosis
1) Idiopathic
2) Postmenopausal
3) Senile
What is the definition of osteopenia
Decreased bone mass that is 1-2.5 SD below the mean
What is the definition of osteoporosis
Bone mass reduction that is at least 2.5 SD below the mean for peak bone mass
How does the diet of a younger female affect her chances of osteoperosis
Insufficiency in calcium uptake in the teenage years cause restriction of the peak bone mass, which sets them up for osteoporosis later in life
What is the mechanism in which menopause can cause osteoporosis
Estrogen deficiency causes the increased resorption and formation of bone, but there is a higher rate of resorption, leading to the increased turnover of bone
*Deceased amount of estrogen leads to the increased number of RANKL and decreased OPG
What are the physical bone findings in the case of osteoporosis due to menopause
Increased osteoclast activity resulting in the thinning of the trabeculae, resulting in microfractures and even the vertebral collapse
What are the physical findings in the case of osteoporosis caused by senile and old age
Cortex of the bone is thinned by subperiosteal and endosteal resorption
*Haversian system is widened
What is the test used to look at the bone density
DEXA scan (wont show up until there is at least 30% of bone loss)
What is the general process of Paget’s disease
Aka osteitis deformans
Increased but disordered and structurally unsound bone mass
What is monostatic Paget’s disease of the bone
Involves a single bone
What is the cause of the majority if the cases of Paget’s disease of the bone
40-50% are familial
In those sporadic cases of Paget’s disease of the bone, what is the mutation and what is its function
SQSTM1 gene, which increased the NFKB and activated osteoclasts
What is the radio graphing finding in the cause of Paget’s disease of the bone
“Cotton wool” with increased uptake on a bone scan
What is the average age that someone with Paget’s disease of the bone will be seen
70 years old
What is the morphology of the bone in Paget’s disease under histology
- Mosiac like pattern that fits together like a jigsaw puzzle
- Prominent cement lines
What are the features of Paget’s disease of the bone in the cause of the lytic phase
Large osteoclasts withe 100 nuclei
What are the features of Paget’s disease of the bone in the cause of the mixed phase
Osteoclasts persist, but there are lots of blasts as well
What are the features of Paget’s disease of the bone in the cause of the final phase
Burned out phase, with the osteoslcerotic phase
What are the clinical features of Paget disease
- Chalk stick type fractures of the long bones
- Hypervasculatiry of the paget bone, leasing to increased warming of the overlying skin and high output heart failure
- Bowing of limbs
What is the seriously complication of Paget’s disease of the bone
High output heart failure due to increased blood flow due to the hypervascularity of the Paget bone
What are the lab values that will be seen in Paget disease of the bone
Increased alk phosphatase
Normal calcium and phosphorous
What is the cause of Rickets, and what is the mechanism
Vitamin D deficiency in children
-Decreased Deposition of bone in the growth plate
What is the cause of osteomalacia and what is the mechanism
Vitamin D deficiency in adults
-None formed during remodeling is undermineralized, leading to increased risk of fractures
What are the clinical features of rickets
- Frontal bossing
- squared off head
- *Rachitic rosary of ribs
- Bowed legs
Which bone condition is present in the case of “railroad tracks” on histology
Dissecting osteitis due to hyperparathyroidism
What is the mechanism of disecting osteitis
Hyperparathyroidism causes the osteoclasts to tunnel into the bone centrally along the length of the trabeculae
What are the bone abnormalities than can be caused by hyperparathyroidism
1) Osteoporosis
2) Dissecting osteoitis
3) Brown tumor
4) osteitis fibrosis cystica
What is the cause of features of a brown bone tumor
Severe form is aka Von Reckilinghausen disease of bone
Hyperparathyroidism leading to microfractures as a result of bone loss. The fractures causes the influx of macrophages and ingrowth fibrosis that creates a mass of reactive tissue
What is the mechanism that renal failure causes changes in pH and bone loss
Tubular dysfunction leads to renal tubular acidosis, which decreases the pH and dissolves the hydroxyapatite, leading to demineralization of the bone