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limbs and back block > cell differentiation: Embryology > Flashcards

cell differentiation: Embryology Flashcards

1
Q

Name the 2 mesodermal domains and where do the signals of each domain originate from?

A

Primaxial - signals from the notochord and neural tube

Abaxial - signals from the lateral plate mesoderm

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2
Q

What is the lateral somatic frontier?

A

Border between the lateral plate mesoderm and each somite

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3
Q

what originates from the abaxial mesodermal domain?

A

Thoracoabdominal muscles

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4
Q

what originates from the primaxial mesodermal domain?

A

Upper limb and neck muscles

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5
Q

what is a myotome (embryological)

A

Part of somite that develops into muscles

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6
Q

What is mesenchyme and where does it arise from?

A

Type of connective tissue found mostly during the development of an embryo. Arises from mesoderm

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7
Q

what is cell differentiation?

A

Process of a cell changing from one cell type to another

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8
Q

In what week does the 4 limbs form?

A

week 4

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9
Q

What does a limb bud consists of?

A

A mesenchymal core (from the parietal/somatic layer of lateral plate mesoderm)
Covered by a layer of cuboidal ectoderm

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10
Q

What does the ectoderm at the distal border of the limb bud thicken to form?

A

Apical ectodermal ridge

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11
Q

What is the apical ectodermal ridge? What occurs there and what arises from it?

A

Key signalling centre
Rapidly proliferating as it is undifferentiated
Where digits from from

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12
Q

What signal initiates limb growth and where does it originate from?

A

FGF 10

comes from lateral plate mesoderm cells

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13
Q

What signal does the dorsal ectoderm release?

A

Signalling molecule: Radical fringe

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14
Q

What signal does the ventral ectoderm release?

A

A transcription factor: Engrailed-1

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15
Q

What signals does the AER express? What do they do?

A

FGF 4
FGF 8

They maintain the undifferentiated zone in the apical ectodermal ridge

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16
Q

What starts differentiation of the proximal (shoulder) part of the limb?

A

Retinoic acid

17
Q

What is the AER controlled by?

A

Mesoderm

18
Q

what process occurs from week 4-8?

A

Limb morphogenesis

19
Q

What happens to the limb bud at week 6?

A

Terminal portion becomes flattened to form hand plates and footplates

20
Q

In what direction does the limb develop?

A

Proximodistally

21
Q

What are the 3 components that the limb develops into? give examples for the leg and arm

A

Stylopod e.g. humerus OR femur
Zeugopod e.g. radius/ulna OR tibia/fibula
Autopod e.g. carpal/metacarpal, tarsal/metatarsal, digits

22
Q

What gene is expressed in overlapping patterns along the length of the whole limb ?

A

HOX 9

23
Q

What do the T-box family transcription factors do?

A

TFs that differentiate the upper and lower limbs

24
Q

What T box- transcription factor differentiates the upper limb?

A

TBX-5

25
Q

What T box- transcription factor differentiates the lower limb?

A

TBX-4 and PITX-1

26
Q

When does apoptosis of the AER occur and what does it allow?

A

When limb bud has proliferated enough to grow a limb.

27
Q

Describe digit formation

A

Apoptosis occurs in the AER to separate ridges into 5 parts (5 digits)
Mesenchyme condenses to form Cartilaginous digits.

28
Q

By what day is digit formation complete?

A

Day 56

29
Q

When does limb rotation occur? describe it

A

Week 7
Upper limbs rotate 90 degrees laterally
Lower limbs rotate 90 degrees medially

30
Q

In limb bone development, expression of what signalling molecule drives cells to differentiate into chondrocytes?

A

BMP

31
Q

At what week does bone ossification occur?

A

Week 8

32
Q

By what week is the primary ossification centre formed?

A

12

33
Q

Define appositional growth?

A

increase in width of bone

34
Q

Define interstitial growth?

A

Increase in length of bone

35
Q

How is endochondral ossification different to • Intramembranous ossification

A

EO: cartilage model is laid down as a precursor to bone
IO: does not involve cartilage

limbs and back block (28 decks)

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