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MSK > Embryology > Flashcards

Embryology Flashcards

1
Q

What are the homeobox genes and how do they affect limb development?

A
  • Homeobox (HOX) genes direct the formation of body structures
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2
Q

What HOX genes are expressed in the formation of the upper limb?

A
  • HOXd 9-13
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3
Q

Which layer of the embryo proliferates to allow the limb buds to elongate?

A

Mesenchyme

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4
Q

Which part of the embryo thickens to form the apical ectodermal ridge?

A

Ectoderm

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5
Q

What type of cells can be found in the mesenchyme adjacent to the apical ectodermal ridge?

A

Undifferentiated, rapidly proliferating cells

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6
Q

What cells differentiate into blood vessels and cartilage and bone?

A

Mesenchymal cells

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7
Q

What is the process responsible for the tissue breakdown in the interdigital regions?

A

Apoptosis

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8
Q

During which week do the peripheral nerves grow from the developing limb plexus (brachial and lumbosacral)?

A

5th week

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9
Q

When is the critical period of limb development?

A

24-36 days after fertilization

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10
Q

What is the total absence of limbs known as?

A

Amelia

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11
Q

What is the partial absence of limbs known as?

A

Meromelia

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12
Q

What is the absence of some long bones known as?

A

Phocomelia

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13
Q

What type of genetic defect is lobster claw foot?

A

Autosomal dominant

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14
Q

What is the condition called where someone has more than 5 digits on their hands or feet?

A

Polydactyly

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15
Q

What is the name of the condition when the webbing between the digits fails to dissapear?

A

Cutaneous syndactyly

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16
Q

During which week of gestation do the limbs begin to appear?

A

Towards end of 4th week

Upper limb starts to appear around Day 24

Lower limb starts to appear around Day 25-26

17
Q

Which cells are responsible for the development of the limbs?

A

Mesenchymal cells

18
Q

From which germ layer do the limbs form?

A

Somatic Lateral Mesoderm

19
Q

Which genes are responsible for limb development?

A

Homeobox genes

20
Q

What are the HOX genes made up from?

A
  • SHH
  • FGF’s
  • WNT-7a
21
Q

On which part of the limb bud can the apical ectodermal ridge be found?

A

At the end of the limb bud

22
Q

Which proteins are responsible for apoptosis?

A

Bone morphogenetic proteins

23
Q

During which weeks do the primary centres of ossification appear?

A

Weeks 8-12

24
Q

What type of ossification do all of the limb bones (except the clavicle) undergo?

A

Endochondrial ossification

25
Q

What type of ossification does the clavicle undergo during embryonic development?

A

Membraneous ossification

26
Q

What is the major difference between endochondrial and membranous ossification?

A

Endochondrial ossification - Cartilage is present

Membranous ossification - No cartilage present

27
Q

By which process is cartilage formed within the embryo during limb development?

A

Chondrification

28
Q

During embryonic development, in which direction do the upper limbs rotate?

A

Laterally by 90 degrees

The extensor muscles therefore are found on the posterior aspects of the upper limbs

29
Q

During embryonic development, in which direction do the lower limbs rotate?

A

90 degrees medially

Extensors are therefore found on the anterior aspect of the lower limb (thigh)

30
Q

What condition results from maternal ingestion of thalidimide during weeks 4-8 of gestation?

A

Meromelia

31
Q

What is this condition known as?

A

Congenital clubfoot (Talipes Equinovarus)

32
Q

In what position are the feet of children born with clubfoot?

A

Sole of foot rotated medially and inverted

33
Q

How common is clubfoot?

A

1 in 1,000 newborns

34
Q

Is syndactyly a common condition?

A

Yes

35
Q

Is syndactyly more common in the foot or hand?

A

Foot

36
Q

What is osseus syndactyly?

A

When notches between digital rays fail to develop

MSK (31 decks)

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