Flashcards in 1.1 Skeletal System Deck (40)
-poor endochondral bone (long bones) formation
-intramembranous (head, chest) not affected
-mutation of FGFR3
-fibroblast growth factor receptor 3
-what is it
-clinical findings (3 big ones)
-congenital defect in Type I collagen synthesis, weak bone
1. multiple fractures--mimic child abuse
2. blue sclera--loss of type I collagen reveals underlying blue choroidal veins
3. hearing loss--middle ear bones fracture
-what is it, etiology
-inherited defect of bone resorption
-results in thick bone that is paradoxically weak.
-Carbonic Anhydrase II mutation--normally required in osteoclasts to excrete H+, providing acidic environment for bone resporption.
-Bone marrow transplant
-osteoclasts come from monocytes
-clinical findings (5 big ones)
1. bone fractures
2. bone impinges into bone marrow--anemia, thrombocytopenia, leukopenia
3. bone impinges on cranial nerves--vision/hearing loss
4. bone narrows foramen magnum--hydrocephalus
5. Renal tubular acidosis--lack of carbonic anhydrase II leads to metabolic acidosis. (CAII required to excrete H+ and reabsorb HCO3-)
Why is bone marrow transplant the Tx for osteopetrosis?
Osteopetrosis is genetic loss of CAII inside osteoclasts, which come from monocytes.
-bone marrow will replace faulty monocytes, which develop into osteoclasts
-low Vit D, leads to low Ca2+ and phosphate, which leads to defective mineralization osteoid
-what osteoblasts produce.
-osteoid is then mineralized with calcium and phosphate to become bone.
-how is it acquired and activated?
-what does is act on?
-diet and UV light
-must be activated:
1. first in liver (to 25-OH-D)
2. then in kidney (to 1,25-OH-D) active form
-increases Ca and phosphate reabsorption from:
-clinical findings, child vs adult
-adult: weak bone
1. pigeon-breast deformity
2. frontal bossing (enlarged forehead)
3. Rachitic rosary ("beads") in costochondral junction
4. bowing of legs
-alkaline phosphatase: high because basic environment necessary for osteoid mineralization by osteoclast (secreted by osteoclast)
3. Low sun exposure
4. Liver disease
5. Kidney disease
-both liver and kidney required to activate Vit D.
-what test used to measure
-DEXA scan to measure bone density
1. Vit D, Calcium, exercise
2. bisphosphonates--induce apoptosis of osteoclasts that eat them
3. estrogen replacement--not recommended
Paget Disease of Bone
'paget's puzzle pieces'
-imbalance btwn osteoclast and osteoblast function
1. osteoclast overactive
2. osteoblast tries to lay down bone in a rush
3. osteoclasts burn out, osteblasts still lay down bone
-induce apoptosis in osteoclasts when they eat them. reduce bone resorption
-Paget's disease of bone
-difference child vs adult
-infection of bone and marrow
-inside bone--abscess (sequestrum) surrounded by sclerosis of bone (involucrum)
-child: metaphysis seeded
-adult: epiphysis seeded
-sclerotic bone tissue that surrounds abscess in osteomyelitis
-abscess in bone from osteomyelitis
what can gas emboli do to bone?
cause ischemia, leading to avascular necrosis
2. direct implantation (penetrating injury)
3. contiguous (direct infection from wound/ulcer)
4. prosthetic infection
direct implantation osteomyelitis
-enjoys living in damp foot under socks and shoes
-diabetic foot ulcer
-think bugs that live in pressure ulcers:
-S aureus, G-'s, strep, anaerobes, candida
-S aureus, strep, G-, TB, salmonella
-what is main pathogen?
-coagulase negative S Aureus.
-likes to adhere to foreign surfaces.
what antibiotic is useful in tx of biofilm organisms?
-think rifampin for prosthetic infections
1. 6 weeks of Abx (not useful in exposed bone)
2. surgery to remove sequestra or prostheses (if Abx fail)
3. Rifampin for biofilm organisms
cell origin of:
1. mesenchymal stem cells
What is master regulator of bone formation?