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Embryology > T15- Development of the back > Flashcards

T15- Development of the back Flashcards

1
Q

What is somitogenesis

A

formation of the somites

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2
Q

When does somitogenesis occur

A

between days 20 and 30

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3
Q

Somitogenesis

What does somitogenesis begin with

A

regression of the primative streak which leaves behind the notochord

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4
Q

Somitogenesis

What happens as the primative streak leaves behind the notochord

A

formation of somitomere pairs occur on either side of the notochord in the cranial reigon

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5
Q

Somitogenesis

After the _____ pair of somitomeres are formed in the _______ reigon, no more somitomeres are formed; instead the ________________ will differentiate into ___________

A

7th; cranial; paraxial mesoderm; somites

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6
Q

Somitogenesis

Where does the first pair of somites appear?

A

in the occipital reigon

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7
Q

Somitogenesis

When does the first pair of somites appear

A

around day 20

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8
Q

Somitogenesis

At what rate do somites form?

A

a rate of about 3 somite pairs/day

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9
Q

Somitogenesis

In total, how many somite pairs will develop?

A

42-44 pairs of somites

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10
Q

Somitogenesis

How many pairs of somites in each reigon

A 
Occipital reigon: 5
Cervical reigon: 8
Thoracic reigon: 12
Lumbar reigon: 5
Sacral region: 5
Cocxygeal reigon: 8-10
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11
Q

Epithelization of somite

What happens when the somite undergoes epithelization

A

it forms around a somitocoel

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12
Q

Epithelization of somite

What happens in the ventral reigon of somite

A

epithelial cells transform back into mesenchyme and are pushed centrally; forms the sclerotome

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13
Q

Epithelization of somite

What do sclerotome cells surround

A

the neural tube and the notochord

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14
Q

Epithelization of somite

What is the sclerotome divided into

A

Dorsal, ventral, lateral and central sclerotome

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15
Q

Epithelization of somite

Where does dorsal sclerotome end up

A

between the neural tube and surface ectoderm

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16
Q

Epithelization of somite

Where does ventral sclerotome end up

A

circling around the notochord

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17
Q

Epithelization of somite

Where does lateral sclerotome end up

A

migrating laterally and ventrally

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18
Q

Epithelization of somite

Where does central sclerotome end up

A

it stays in close connection with the dermatome

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19
Q

Epithelization of somite

What happens to the dorsal reigon of the somite

A

it becomes the dermomyotome

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20
Q

Epithelization of somite

How is the myotome formed?

A

cells from the VLL and DML transform back into mesenchyme and migrate beneath the dermatome

21
Q

Epithelization of somite

Where is the VLL and DML originally located

A

on either side of the dermatome

22
Q

Epithelization of somite

Where is the dermatome originally located?

A

between the VLL and the DML

23
Q

Somite polarization: sclerotome polarization

Which protiens induce the ventral part of the somite to form into sclerotome

A

SHH from the floor of the neural tube and NOGGIN from the notochord

24
Q

Somite polarization: sclerotome polarization

Which protien does the sclerotome express

A

PAX-1

25
Q

Somite polarization: sclerotome polarization

What does PAX-1 control

A

vertebrae formation and chondrogenesis

26
Q

Somite polarization: Polarization of Myotome (DML)

Which protiens is the DML influenced by

A

WNT protiens

27
Q

Somite polarization: Polarization of Myotome (DML)

Where do the WNT protiens come from

A

the dorsal aspect of the neural tube

28
Q

Somite polarization: Polarization of Myotome (DML)

What does WNT instruct the cells of the DML to do

A

To differentiate into muscle precursor cells and to express the muscle gene MYF5

29
Q

Somite polarization: Polarization of Myotome (DML)

What do the cells of the DML become

A

muscles of the ventrolateral wall and the flexors of limbs

30
Q

Somite polarization: Polarization of Myotome (VLL)

Which protiens are the cells of the VLL influenced by

A

WNT protiens which come from the overlying ectoderm and BMP4 from lateral plate mesoderm

31
Q

Somite polarization: Polarization of Myotome (VLL)

BMP4 has what type of influence on cells of VLL

A

inhibiting influence

32
Q

Somite polarization: Polarization of Myotome (VLL)

What do the cells of the VLL become due to protien influence

A

muscle precursor cells

33
Q

Somite polarization: Polarization of Myotome (VLL)

What protien do the muscle precursor cells express

A

MYOD

34
Q

Somite polarization: Polarization of Myotome (VLL)

What do muscle precursor cells go on to become

A

intrinsic back muscles and extensors of the limb

35
Q

Somite polarization: Polarization of Dermatome

Which protien influences the dermatome cells

A

NT-3 from the dorsal neuraltube

36
Q

Somite polarization: Polarization of Dermatome

What protien does the dermatome cells express as a result of protien influence

A

PAX3

37
Q

Formation of vertebrae: Resegmentation of sclerotome

How does the sclerotome resegment?

A

The sclerotome forms clusters so that individual bones can be formed, and each sclerotome cluster divides into a cranial portion and a caudal portion

38
Q

Formation of vertebrae: Resegmentation of sclerotome

What does the cranial and caudal portions of each sclerotome consist of

A

cranial portion: loosely packed cells

caudal portion: densely packed cells

39
Q

Formation of vertebrae: Resegmentation of sclerotome

The vertebral body is formed from what parts of the sclerotome

A

The caudal half of the cranial sclerotome and the cranial half of the caudal sclerotome

40
Q

Chondrification of vertebrae

What does the costal process become

A

The transverse process

41
Q

Chondrification of vertebrae

What does the centrum become

A

The vertebral body

42
Q

Chondrification of vertebrae

What is the chondrification center

A

the site where mesenchyme turns into cartilage

43
Q

Chondrification of vertebrae:

When does formation of the chondrification center occur

A

about 6 weeks into development

44
Q

Ossification of vertebrae

When do primary ossification centers appear

A

at about 7 weeks

45
Q

Ossification of vertebrae

When can ossification centers in the neural arch be seen

A

in the 8th week

46
Q

Ossification of vertebrae

When does full ossification of the cartilagenous process complete

A

at about age 25

47
Q

Normally, _________ chondrification centers fuse at the end of the _________ to form the ____________

A

two; embryonic period; cartilagenous centrum

48
Q

__________ failure of ________ chondrification center results in________

A

unilateral; one; hemivertebra

Embryology (14 decks)

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