1.1 Skeletal System Flashcards Preview

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Flashcards in 1.1 Skeletal System Deck (40)
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1

Achondroplasia
-clinical findings
-etiology

-dwarfism

-poor endochondral bone (long bones) formation
-intramembranous (head, chest) not affected

-mutation of FGFR3
-fibroblast growth factor receptor 3
-auto dominant

2

osteogenesis imperfecta
-what is it
-clinical findings (3 big ones)

-congenital defect in Type I collagen synthesis, weak bone
-auto dom.

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

3

Osteopetrosis
-what is it, etiology
-Tx

"rock like"
-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

4

Osteopetrosis
-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-)

5

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

6

Osteomalacia (Ricketts)
-etiology
-clinical findings

-low Vit D, leads to low Ca2+ and phosphate, which leads to defective mineralization osteoid

7

osteoid

-what osteoblasts produce.
-osteoid is then mineralized with calcium and phosphate to become bone.

8

Vit D:
-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:
1. GI
2. Bone
3. Kidney

9

Osteomalacia (Ricketts)
-clinical findings, child vs adult

-adult: weak bone

-child:
1. pigeon-breast deformity
2. frontal bossing (enlarged forehead)
3. Rachitic rosary ("beads") in costochondral junction
4. bowing of legs

10

osteomalacia (Ricketts)
-lab findings:
-calcium
-phosphate
- PTH
-alkaline phosphatase

-calcium: low
-phosphate: low
-PTH: high
-alkaline phosphatase: high because basic environment necessary for osteoid mineralization by osteoclast (secreted by osteoclast)

11

Osteomalacia (Ricketts)
-causes (5)

1. Diet
2. Malabsorption
3. Low sun exposure

4. Liver disease
5. Kidney disease
-both liver and kidney required to activate Vit D.

12

Osteoporosis
-what test used to measure

-DEXA scan to measure bone density

13

Osteoporosis
-lab values:
-calcium
-phosphate
-PTH
-alkaline phosphatase

all normal

14

Osteoporosis:
-tx
-contraindications

1. Vit D, Calcium, exercise
2. bisphosphonates--induce apoptosis of osteoclasts that eat them
3. estrogen replacement--not recommended
4. glucocorticoids--contraindicated

15

Paget Disease of Bone
-etiology, mech
-stages

'paget's puzzle pieces'
-imbalance btwn osteoclast and osteoblast function
-3 stages:
1. osteoclast overactive
2. osteoblast tries to lay down bone in a rush
3. osteoclasts burn out, osteblasts still lay down bone

16

bisphosphonates

-induce apoptosis in osteoclasts when they eat them. reduce bone resorption
-tx in:
-Paget's disease of bone
-Osteoporosis

17

Osteomyelitis
-etiology
-clinical findings
-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

18

involucrum

-sclerotic bone tissue that surrounds abscess in osteomyelitis

19

sequestrum

-abscess in bone from osteomyelitis

20

what can gas emboli do to bone?

cause ischemia, leading to avascular necrosis

21

osteomyelitis:
categories

1. hematogenous
2. direct implantation (penetrating injury)
3. contiguous (direct infection from wound/ulcer)
4. prosthetic infection

22

direct implantation osteomyelitis
-what pathogens?

-pseudomonas
-enjoys living in damp foot under socks and shoes

23

contiguous osteomyelitis
-common cause?
-what pathogens?

-diabetic foot ulcer
-think bugs that live in pressure ulcers:
-S aureus, G-'s, strep, anaerobes, candida

24

hematogenous osteomyelitis
-what pathogens?

-S aureus, strep, G-, TB, salmonella

25

prosthetic osteomyelitis
-what is main pathogen?

-coagulase negative S Aureus.
-likes to adhere to foreign surfaces.

26

what antibiotic is useful in tx of biofilm organisms?

Rifampin.
-think rifampin for prosthetic infections

27

osteomyelitis
-describe tx

-difficult tx
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

28

cell origin of:
-osteoblasts
-osteocytes
-osteoclasts

1. mesenchymal stem cells
2. osteoblasts
3. monocytes

29

What is master regulator of bone formation?

RUNX2
(aka CBFA-1)

30

what do osteocytes secrete to resorb bone?
2 things

1. H+
2. cathepsin K