ToB 19 Embryology 3 - Mesoderm Flashcards

1
Q

Which germ layer present at the end of week 3 will give rise to the biggest variety of tissues and structures?

A

Mesoderm

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2
Q

Which germ layer present at the end of week 3 will give rise to tissues and structures that maintain contact between the inside and outside world? Ie: Brain, spinal cord, epidermis, retina etc.

A

Ectoderm

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3
Q

Which germ layer present at the end of week 3 will give rise to the neural tube?

A

Ectoderm

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4
Q

Why does part of the ectoderm layer become neuroectoderm?

A

The ectoderm directly above the notochord is changed to neuroectoderm via signal molcules released by the notochord.

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5
Q

The newly formed neuroectoderm forms a plate called:

A

Neural plate

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6
Q

How does the neural plate become the neural tube?

A

The notochord signals for the neural plate to thicken.

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7
Q

What shape is the neural plate?

A

Keyhole shaped

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8
Q

What is the name given to the part of the mesoderm layer which arranges itself around the neural tube?

A

Paraxial mesoderm

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9
Q

After formation of the neural tube, 4 different types of mesoderm are created. Name them:

A

1- Paraxial
2- Intermediate
3- Somatic
4- Splanchnic

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10
Q

What is the name of the u-shaped cavity which separates part of the mesoderm, creating the somatic mesoderm and splanchnic mesoderm?

A

Intraembryonic coelom

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11
Q

In which week after fertilisation does the neural tube and intaembryonic coelom form?

A

Week 4

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12
Q

Define splanchnic:

A

Relating to the viscera/ internal organs

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13
Q

What is the name of the part of the mesoderm layer which is segmented into somites?

A

Paraxial mesoderm

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14
Q

Define somite:

A

Bilaterally paired blocks of paraxial mesoderm which form along the head-to-tail axis

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15
Q

On which day after fertilisation do the first somites appear?

A

Day 20

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16
Q

Where do the first pair of somites appear?

A

Occipital region (base of skull)

17
Q

Approximately how many somite pairs are present by the end of week 5 (after fertilisation)?

A

~ 42-44 pairs

18
Q

The somites give rise to which tissue types?

A

1-Dermatome
2-Myotome
3-Sclerotome

19
Q

Which 2 bone structures are formed from the Sclerotome?

A

1- Ribs

2- Vertebrae

20
Q

What is the final number of somites formed?

A

31 pairs

21
Q

What is the difference between the epimere and hypomere?

A

Epimere

  • Formed from DORSAL myotome cells
  • Innervated by DORSAL branch of spinal nerve
  • Forms back muscles

Hypomere

  • Formed from VENTRAL myotome cells
  • Innervated by VENTRAL branch of spinal nerve
  • Forms muscles of ventral body wall and limbs
22
Q

The epimere is innervated by which branch of the spinal nerve?

A

Dorsal

23
Q

The hypomere is innervated by which branch of the spinal nerve?

A

Ventral

24
Q

The epimere will give rise to muscles where?

A

Back muscles

25
Q

The hypomere will give rise to muscles where?

A

Ventral body wall and limbs

26
Q

How many pairs of spinal nerves present in a body?

A

31 pairs

27
Q

What can a single spinal nerve innervate?

A

The myotome or dermatome which differentiated from the same somite as the specific spinal nerve. (Same derivative)

28
Q

How is there no overlap between the presence of spinal nerves?

A

Due to segmentation the spinal nerves can only innervate tissue from the same derivative (as the nerve)

29
Q

What system does the intermediate mesoderm give rise to?

A

Urogenital system

30
Q

What tissue doe the somatic mesoderm give rise to?

A

Connective tissue of limbs

31
Q

What tissues does the splanchnic mesoderm give rise to?

A

Smooth muscle, connective tissue and vasculature of gut

32
Q

What of the 3 germ layers grows the fastest?

A

Ectoderm

33
Q

In which week after fertilisation does embryonic folding occur?

A

Week 4

34
Q

What name is given to the embryonic folding that results in the head and tail end of the embryo to be folded under?

A

Cephalocaudal folding

35
Q

What are the names of the 2 embryonic folds which create a body encased in ectoderm, with one opening for the umbilical cord?

A

1- Cephalocaudal folding

2- Lateral folding

36
Q

Embryonic folding only creates one opening into the embryo. What is this opening for?

A

Umbilical cord

37
Q

What event causes the embryonic disk to be suspended within the amniotic sac?

A

Embryonic folding