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Medicine 2.1 > Muscle Ebryology > Flashcards

Muscle Ebryology Flashcards

1
Q

What is gastrulation?

A

-Process of cell division and migration resulting in formation of 3 germ layers.

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2
Q

How does gastrulation occur?

A

-Cells migrate towards raised primitive streak and push downwards into epiblast layer, then pushes hypoblast out of the way to form 3 layers.

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3
Q

What is the mesoderm important for?

A

-It is the building block of all muscle

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4
Q

What distinct regions does the mesoderm divide into?

A
  • Paraxial mesoderm
  • Intermediate mesoderm
  • Lateral plate mesoderm
  • Extraembryonic mesoderm
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5
Q

When does the mesoderm differentiate?

A

-Between days 17 and 21

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6
Q

What is the notochord and its function?

A

-Area in the middle with thickened cells that is a signalling centre that controls specification of surrounding cells.

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7
Q

Why do the oropharyngeal and cloacal membrane have no mesoderm layer?

A

-They will break down to form the mouth and the anus.

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8
Q

What does the paraxial mesoderm form?

A

-Somites in the embryo

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9
Q

How does the paraxial mesoderm form and where does it lie?

A
  • Forms from cells moving bilaterally and cranially from the primitive streak.
  • Lies adjacent to notochord and neural tube
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10
Q

What does the intermediate mesoderm form?

A

-Genitourinary system

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11
Q

What 2 layers does the lateral plate mesoderm divide into?

A
  • Somatic or parietal layer

- Splanchnic or visceral layer

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12
Q

What cavity splits the 2 lateral plate mesoderm layers?

A

-Intraembryonic coelom

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13
Q

What area of the mesoderm forms skeletal muscle?

A

-Paraxial mesoderm

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14
Q

What area of mesoderm forms smooth muscle (gut and derivatives)?

A

-Visceral layer, lateral plate mesoderm around the gut tube

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15
Q

What area of mesoderm will form smooth muscle (pupils, mammary and sweat glands)?

A
  • Not mesoderm

- Ectoderm

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16
Q

What area of mesoderm will form cardiac muscle?

A

-Visceral layer, lateral plate mesoderm around heart tube.

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17
Q

What does the paraxial mesoderm get organised into?

A

-Somites

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18
Q

Where and when do somites form?

A

-Form along side the developing neural tube in a craniocaudal sequence over time from day 20

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19
Q

What rate do somites appear and why can this be useful?

A
  • Appear at approx. 3 pairs a day until the end of week 5.

- Useful as can be used to accurately determine age of the embryo by counting no. of pairs.

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20
Q

What transition does mesenchymal cells undergo during somite formation?

A

-Mesenchumal to epithelial transition

21
Q

What is the unsegmented mesoderm called?

A

-The pre somitic mesoderm

22
Q

What happens to the pre somitic mesoderm before it segments?

A

-It gets patterned and many molecular factors are involved in this process. Including the notochord.

23
Q

What are some of the molecules that are involved in somite formation?

A
  • FGF
  • Wnt
  • Notch
24
Q

Describe the clock and wave mechanism to regulate somite formation?

A
  • Genes tell cells to switch between a permissive and non-permissive state in a constantly timed fashion (notch).
  • A wave of factors sweeps along the length of the embryo and interacts with the cells that are permissive at the right time in the right area. (FGF 8)
  • The process is helped along by Wnt.
  • In summary, overlapping gradients control somite formation.
25
Q

By then end of week 5 around how many somites are formed and what will these go onto form?

A
  • By the ned of week 5, 42-44 pairs are present.

- These will go onto form the axial skeleton

26
Q

What happens to somites when they have formed?

A

-They start to differentiate

27
Q

How does somite differentiation occur?

A
  • By start of week 4, cells in the ventral and medial wall of somites start to lose epithelial characteristics and become mesenchymal like again.
  • This portion is calles the sclerotome.
  • Cells at the dorsal half form the dermomyotome.
28
Q

What does the sclerotome go onto form?

A

-Ribs and vertebrae

29
Q

What happens to the dermomyotome?

A
  • It splits again to form the: -dermatome

- myotome

30
Q

What does the dermatome go onto form?

A

-Dermis of the back

31
Q

What does the myotome go onto form?

A

-Muscles

32
Q

What are myoblasts?

A

-Muscle cell precursors

33
Q

What are myocytes and how would they form?

A

-Are mature muscle cells formed from myoblasts

34
Q

How do myoblasts differentiate?

A

-Myoblasts undergo cell division under the influence of growth factors.

35
Q

What happens to myoblasts when there is depletion of growth factors?

A
  • they stop dividing

- Secrete formation onto ECM and bind to it via integrin crucial step

36
Q

How do myoblasts differentiate into myotubes?

A
  • Myoblasts align into chains and fuse, cell membranes disappear and mutinucleated myotubes from (primary myotubes).
  • Myogenin mediates this differentiation.
37
Q

What regulates the development of muscle?

A

-Genes and myogenic factors eg. MYOD, MYO5

38
Q

What are MYOD and MYF5 and what do they do?

A
  • Transcription factors
  • Activate muscle specific genes
  • Enable differentiation of myogenic precurosrs in the dermomyotome into myoblasts
  • Are very powerful as they can convert non muscle cells into cells expressing all muscle proteins.
39
Q

What happens at the neural tube that helps regualte muscle development?

A

-Wnt proteins (activate) and BMP proteins (inhibit) combine to activate MYOD in the dermomyotome; creating a group of muscle cell precursors, which express MYF5.

40
Q

What happens at the notochord to regulate muscle development

A

-Sonic hedgehog and noggin induce sclerotome formation.

41
Q

What happens at the lateral plate mesoderm that regulated muscle development?

A

-Wnt and BMP activate MYOD and MYF5

42
Q

What does smooth muscle (apart from cilliary muscle, sphincter pupillae of eye (ectoderm)) originate from?

A

-Splanchnic mesoderm/visceral mesoderm

43
Q

What is responsible for smooth muscle cell differentiation?

A

-Serum response factor (SRF)

44
Q

What can enhance SRF activity?

A
  • Upregulated by kinase phophorylation pathways

- Myocardin related transcription factors enhance SRF activity.

45
Q

How is skeletal muscle formed and what controls this?

A
  • Myoblasts fuse to form long multinucleated fibres (myotubes)
  • Controlled by MYOD, MYF5, Myogenin
46
Q

What are tendons derived from and what controls this?

A

-Derived from sclerotome and under control of TF scleraxis.

47
Q

What does cardiac muscle originate from?

A

-Splanchnic/viseceral mesoderm surrounding the developing heart tube.

48
Q

What genes are and arent involved in early cardiac muscle development?

A
  • IS tinman

- Isnt MYOD

49
Q

How do myoblasts adhere in cardiac muscle?

A

-Via intercalated discs

Medicine 2.1 (29 decks)

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