MSK Pt 1 Flashcards

1
Q

The skeleton is composed of? (2 tissues, 3 cell types)

A

bone/cartilage

osteoblasts/osteoclasts/chrondrocytes

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2
Q

Skeletal tissue is derived from three embryonic cell lineages. What are they?

A

cranial neural crest cells (head)
paracial mesoderm cells/somites (axial skel)
lateral plate mesoderm (limbs)

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3
Q

Limb buds begin to develop during the _____ week.

A

4th

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4
Q

What are the 4 steps of skeletogenesis?

A

patterning
organogenesis
growth
homeostasis

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5
Q

When can we see limb buds?

A

7th week (I’m pretty sure in OB we learned wk 9 buuuuuut what else is new)

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6
Q

What can we see during the 9-11th week?

A

clavicle + mandible

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7
Q

When do we see hands and feet?

A

12-14wks

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8
Q

When do we see the distal femoral epiphysis? The proximal tibial epiphysis?

A

29-34wks

35wks

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9
Q

How is the femur length measured?

A

b/w the distal and proximal ossification centres of the femoral diaphysis

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10
Q

The cardio-thoracic circumference ratio increases through gestation, but should not measure more than ______. What can it indicate if the ratio is increased?

A

0.5

cardiac- fetal cardiomegaly
thoracic- pulmonary hypoplasia

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11
Q

Thoracic/abdominal circumference should measure _____ after 20 weeks.

A

> 0.8

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12
Q

Skeletal dysplasia aka

A

dwarfism

umbrella term for conditions affecting bone and cartilage growth

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13
Q

The most common severe skeletal dysplasias manifest with:

A
severe micromelia (shortening of all limbs)
and thoracic dysplasia
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14
Q

Most common types of skeletal dysplasias can be detected by what?

A

FL

if it’s 1-4mm below 2 SD points, more measurements are required.
If it’s 5mm below 2 SD points, there’s a high likelihood of SD

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15
Q

What helps distinguish skeletal dysplasia from severe IUGR?

A

femur length to foot length ratio

*foot length is not affected with most SD so the ratio is decreases

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16
Q

What are the 4 patterns of shortening of the long bones?

A

rhizomelia: proximal segment (femur, hum)
mesomelia: middle segment (radius, ulna, tib/fib)
acromelia: distal segment (hands + feet)
micromelia: entire limb (mild, bowed, severe)

17
Q

What type of skeletal dysplasia is lethal?

A

severe micromelia

earlier the diagnosis, the worse the prognosis

18
Q

Thoracic dysplasia is associated with:

A

pulmonary hypoplasia

heart may appear abnormally enlarged–pseudocardiomegaly

19
Q

What are the signs of pulomary hypoplasia:

A

narrow AP diameter of chest (<0.8)
dec thoracic circum (measure @ level of 4CH)
short ribs (normally encircle 70-80% of thorax)
abnormal contour thorax in coronal (bell shaped)
dec thoracic length (apex–>diaphragm)

20
Q

Frontal bossing:

A

development of an unusually pronounced forehead bc of enlargement of frontal bone

21
Q

What is the first bone in the fetal limb to develop?

A

humerus

22
Q

What step of skeletogenesis determines the final size of bone?

A

patterning

23
Q

How do fetal biometric ratios help in the diagnosis of skeletal dysplasia?

A

FL/HC ratio < 3 SD below the mean suggests SD