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Flashcards in MSK Deck (43):
1

Layers of the epidermis

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

2

includes claudins and occludins
prevents paracellular movement of solutes

tight junction

3

calcium-dependent adhesion proteins

cadherins

4

impaired cartilage proliferation in the growth plate
mutation of FGFR3 (gain of function) -> receptor normally inhibits cartilage proliferation
AD
short extremities with normal sized head (skull) and chest (ribcage) -> intramembranous bone formation not affected (flat bones okay)
mental function, life span & fertility not affected

achondroplasia = dwarfism

5

bone formation of a cartilage matrix which is replaced by bone

endochondral bone formation
(long bones)

6

Congenital defect of bone formation resulting in structurally weak bone
AD
defect in type I collagen synthesis
multiple bone fx (looks like child abuse?)
Blue sclera -> normally contains type I collagen -> blue due to exposure of the choroidal veins
hearing loss (fx of bones of middle ear)

Osteogenesis Imperfecta

7

Inherited defect of bone resorption (defect in osteoclasts)
thick, heavy bone that fractures easily -> like chalk
due to poor osteoclast function
Bony replacement of marrow causes anemia, thrombocytopenia, leukopenia with extramedullary hematopoiesis
vision impairment -> cranial nerve impingement
hydrocephalus -> narrow foramen magnum
RTA -> mutation in carbonic anhydrase results in decreased resorption of bicarb -> metabolic acidosis
(Note: acidic environment is needed to remove calcium from the bone during resorption)

Osteopetrosis

Tx: bone marrow transplant (osteoclasts are derived from monocytes)

8

Defective mineralization of osteoid
low levels of Vit D, resulting in low serum calcium & phosphate
child presents with:
pigeon-breast deformity -> pull of resp muscles on rib cage
frontal bossing (enlarged forehead)
bowed legs

Rickets

In adults, it is called Osteomalacia
weak bone with increased risk of fx
Lab: decreased Ca2+, phosphate; increased PTH & ALP
*whenever osteoblasts are active, ALP is elevated -> create an alkaline environment for osteoid to be laid down

9

reduction in trabecular bone mass
porous bone with increased risk of fx (hip, distal radius, vertebrae)
most common forms: senile & postmenopausal
measure bone loss with DEXA scan
Labs are normal -> excludes osteomalacia

osteoporosis

10

when does peak bone mass typically occur?

age 30

11

Imbalance of osteoclast and osteoblast function
late adulthood (age 60 yr)
localized process*
Result: thick sclerotic bone that fractures easily
Bx: mosaic pattern of lamellar bone (osteoblast trying to lay down bone but not in balance)
Increased hat size
bone pain from microfractures
hear loss
lion-like facies
**high ALP** with normal calcium, phosphate, PTH

Paget Disease

Tx: calcitonin -> inhibits osteoclasts
bisphosphonates -> induce osteoclast apoptosis
complication: osteosarcoma

12

Infection of marrow and bone, usually in children
hematogenous spread -> seeds metaphysis
most common cause: Staph aureus
Presentation: bone pain, fever, leukocytosis
XR: lytic focus (abscess) aka sequestrum surrounded by sclerosis aka involucrum

osteomyelitis

13

infection of vertebrae from TB

Pott disease

14

most commonly fractured bone in the wrist
susceptible to AVN

scaphoid bone (thumb side of the wrist)

15

femoral head fracture that disrupts blood supply

subcapsular

16

AVN of ossification centers in children

osteochondrosis
Caused by Legg-Calve-Perthes

17

lilac discoloration of upper eyelids
scaly erythematous eruptions on knuckles, elbows & knees
muscle weakness: getting up from chair or climbing stairs
B cells & CD4 T cells in muscle

dermatomyositis

If juvenile onset: rash, abdominal pain, calcinosis

18

CD8 T cells and macrophages around & in muscle
symmetric proximal muscle involvement
intracellular deposition of amyloid
no skin involvement
may involve heart, lungs, bvs

polymyositis

19

immune mediated loss of AChR
female
ptosis and diplopia
thymic hyperplasia -> improvement after thymectomy

myasthenia gravis

20

seen with small cell carcinoma
muscle weakness that improves with repeated use
Fewer ACh vesicles released with action potential
Does not respond to AChE inhibitors

Lambert-Eaton myasthenic syndrome

21

decoy receptor made by osteoblasts
short-circuits RANKL

osteoprotegrin (OPG)

22

missense mutation of fibrillin
fibrillin in microfibrils normally sequesters TGF-beta, so in this case TGF-beta stays activated, causing damage
dislocation of lens
Cardiac risks: MVP & aortic dissection (cystic media necrosis)

marfan syndrome

23

defect in fibrillar collagen
○ Skin is hyperextensible & joints are hypermobile
○ Predisposition to joint dislocation
○ Skin is stretchable and extremely fragile; vulnerable to trauma. Surgical repair is difficult
○ Internal complications also possibly present: colon rupture, large arteries, ocular fragility, rupture of cornea & retinal detachment, diaphragmatic hernia

Ehlers-Danlos syndrome

24

Prevents damage to msk system by inhibiting muscle contraction when a muscle exerts too much force

Golgi tendon organs (GTO)
It is a negative feedback system that regulates and maintains muscle tension

25

fracture of the distal radius

Colles fracture

26

most common adult sarcoma
typically on thigh or retroperitoneum

liposarcoma
lipoblasts identified with fat stains

27

benign heart tumor associated with tuberous sclerosis

rhabdomyoma

28

pain, numbness, paresthesias of thumb, index finger, 2nd or 3rd finger
thenar atrophy produces "ape hand"

carpal tunnel syndrome
Tinel sign
Phalen maneuver

29

atrophy of type I fibers
inability to relax muscles (sustained grip)
see: sagging face, frontal balding, testicular atrophy

myotonic dystrophy
muscle wasting and cardiac dysfunction cause death

30

type of hypersensivity reaction associated with myasthenia gravis

Type II
antibodies inhibit or destroy ACh receptors

31

gram + anaerobe that produces alpha-toxin (lecithinase)
damages cells membranes & can cause hemolysis
gas gangrene

Clostridium perfringens
tx: PCN G + clindamycin
hyperbaric oxygen

32

fibromatous tumor of the anterior abdominal wall in women
associated with previous trauma, FAP & Gardner syndrome

desmoid tumor

33

fibromatosis involving palmar fascia
causes contracture of single or mult fingers -> hooklike deformity
assoc with alcoholism, DM, epilepsy

Dupuytren contractures

34

dystrophic calcification which is visible on xray
larvae encyst in striated muscle

trichinella spiralis
undercooked pork, bear & seal
periorbital edema
splinter hemorrhages in nails
tx: albendazole

35

neurotoxin binds to spinal afferent fibers and inhibits release of glycine and GABA in spinal cord
sustained motor stimulation of voluntary muscles

clostridium tetany
begins with stiffness in the jaw that is painful
vaccine: tetanus toxoid

36

septic arthritis after UG infection
affects wrists and ankles

N gonorrhoeae
tx: ceftriaxone

37

most common cause of nongonococcal septic arthritis

Staph aureus
tx: nafcilin & 3rd gen cephalosporin

38

bone of the hand that is prone to avascular necrosis due to its retrograde blood supply

scaphoid

39

compression of ulnar nerve at wrist or hand
seen in cyclists

Guyon canal syndrome

40

compression of lower trunk of brachial plexus and subclavian vessels

thoracic outlet syndrome
results in claw hand (? like Klumpke palsy from grabbing tree branch when falling)

41

nerve affected by anterior dislocation of humerus

axillary
see flat deltoid

42

nerve damaged by midshaft humoral fracture, crutches or sleeping with arm over chair

radial

43

nerve affected by fracture of medial condyle of the humerus or hook of the hammate

ulnar