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CT MSK > Limb Development > Flashcards

Limb Development Flashcards

1
Q

For the upper limb, describe Prexial and Postaxial

A

Preaxial is thumb and radius

Postaxial is pinky and ulna

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2
Q

What week do limb buds begin forming?

A

Week 4

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3
Q

What week do digits begin forming?

A

Week 8

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4
Q

Primary ossification centers form during which week?

A

Week 12

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5
Q

Muscles of limbs come from what?

Cartilage of the limbs and connective tissue come from what?

A

Somite mesoderm

Somatic lateral plate mesoderm

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6
Q

In the limb, the mesoderm releases what factor to stimualte the surface ectoderm to induce the formation of the Apical Ectodermal Ridge?

What does the AER give off?

A

FGF10

Limb bud

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7
Q

As the Apocal Ectodermal ridge forms it grows in what direction?

A

Proximally to Distally

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8
Q

What is the stylopod?

A

Humerus

Femur

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9
Q

What is the zeugopod?

A

Radius and Ulna

Tibia and Fibula

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10
Q

What do autopods become?

A

Carpels, Metacarpals, Digits

Tarsals, Metatarsals, Digits

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11
Q

What week do hand and foot plates appear?

What week do chondrification centers appear?

A

Week 5

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12
Q

Digital rays of the hands, and the entire limb skeleton (cartilagenous) appears at what week?

A

Week 6

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13
Q

What week do the digital rays of the feet, and osteogenesis of long bones begin?

A

Week 7

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14
Q

What week does rotation of the limbs occur?

A

Week 7

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15
Q

What week do seperate digits form through apoptosis?

What signalling factor is responsible for this digital apoptosis?

A

Week 8

BMP

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16
Q

Why is it that upper limbs form before lower limbs?

A

Blood supply is being shunted to the brain, and upper limbs are closer to this supply (i.e. more nutrients)

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17
Q

Describe the direction of rotation of limbs that occurs during Week 7?

Upper Limbs vs Lower Limbs

A

Upper limbs rotate 90 degrees Laterally

Lower limbs rotate 90 degrees Medially

18
Q

Nerves start innervating the developing muscles at what week?

A

Week 5

19
Q

Muscles of the limbs are derived from what portion of the somites?

A. Ventrolateral

B. Ventromedial

C. Dorsolateral

D. Dorsomedial

A

Dorsolateral

20
Q

Motor axons from the spinal cord enter the limb buds during the 5th week, and are derived from what?

A

Neuralectoderm

21
Q

Sensory neurons come from ________ and use ________ as a guidance.

A

Sensory neurons come from neural crest and use motor axons as a guidance.

22
Q

At week 5 upper and lower limbs start growing out in what direction?

A

Laterally and caudally

(out and down)

23
Q

At week 6, upper and lower limbs bend in what direction?

A

Anteriorly

24
Q

Is Barber pole rotation is seen in the upper or lower limb?

A

Lower limb

25
Q

What artery comes off the dorsal aorta and supplies the upper limb buds?

What artery does it become within the limb bud?

A

Intersegmental arteries from the dorsal aorta

Becomes the primary axial artery

26
Q

The primary axial artery in the upper limb later becomes what structure?

The primary axial artey of the lower limb becomes what structure?

A

Upper limb: brachial artery

Lower limb: deep artery of the thigh

27
Q

What is the most common musculoskeletal defect?

What is the presentation

A

Club foot or Talipes Equinovarus

Sole of foot is turned medially with foot inverted

28
Q

Which of the following is true in Developmental Hip Dysplasia?

A. More common in females than males

B. Caused by under development of acetabulum of the hip bone

C. Caused by generalized joint laxity

D. All of the above

A

All of the above

A. More common in females than males

B. Caused by under development of acetabulum of the hip bone

C. Caused by generalized joint laxity

29
Q

Positioning and shape of the limbs is regulated by turning what signalling molecule on and off?

A

Hox genes

30
Q

Proximal to distal growth and patterning of the limbs is determined by what?

Describe the signaling cycle that occurs

A

Apical Ectodermal Ridge

FGF10 released by mesenchyme to AER

AER release of FGF-8 and FGF-4 to mesoderm

this is how we get the stylopod, zeugopod, and autopods

31
Q

Dorso-ventral patterning also involves the AER, but instead two other signalling factors specific to dorsal or ventral side. What is the signalling factor for the dorsal surface, and what is the signalling factor for the ventral surface?

A

VEntral surface: BMPs

Dorsal Surface: Wnt7

32
Q

Anterior (preaxial) and posterior (post-axial) patterning of the limb is established by what structure?

What side of the limb does this structure work on?

What signalling factors are involved?

A

Zone of Polarizing Activity works on the Posterior side and releases Shh and retinoic acid

33
Q

Loss of ZPA would result in which of the following?

A. Additional posterior elements (polydactyly)

B. Loss of posterior elements

C. Duplication of posterior elements (little fingers on both sides of the thumb)

A

Loss of posterior elements

34
Q

Upregulation of ZPA signals retionoic acid and Shh results in what?

A. Additional posterior elements (polydactyly)

B. Loss of posterior elements

C. Duplication of posterior elements (little fingers on both sides of the thumb)

A

Additional posterior elements (polydactyly)

35
Q

T/F: Posterior elements like little finger and ulna are formed prior to anterior elements like thumb and radisu

A

True

36
Q

What is the mechanism of this disease?

What week would this happen?

A

Upregulation of the ZPA

Week 6 (formation of the digital rays of the hand)

37
Q

What is the mechanism of this disease?

What week does this occur?

A

Duplication of ZPA

Week 7 (formation of digital rays of foot plate)

38
Q

Shown below are two defects on the left structure.

What is the name of both abnormalities?

What is the cause of the one specific to this lecture?

When does this issue occur?

A

Syndactyly: problem of BMP regulation

Week 8

Brachydactyly

39
Q

Pictured below is a form of miromelia, called Phocomelia where hands/feet attach close to the body.

What is the mechanism of this abnormality?

In what week does it occur

A

Problem with FGF signalling and the Apical Ectodermal Ridge

Week 4 - Week 8

Happens between Week 4-week 8 because proximal to distal growth occurs during this time

40
Q

What is the disease pictured below?

In what week does this abnormality develop?

A

Amelia

Week 4: a limb bud wasn’t even developed for upper limbs

problem with Apical ectodermal ridge

41
Q

What is the name of the abnormality pictured below?

What is the mechanism of this abnormality?

A

Ectodactyly or Forked Hand/Foot

Center of the AER did not develop properly

CT MSK (20 decks)

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