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Embryology > Lecture 10 (Exam 2) > Flashcards

Lecture 10 (Exam 2) Flashcards

1
Q

This zone of mesoderm is a thick column closest to and parallel with the notochord. It becomes segmented into somites.

A

Paraxial mesoderm (segmental plate)

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2
Q

This zone of mesoderm is narrow column lateral to the paraxial mesoderm and gives rise to the urogenital system.

A

Intermediate mesoderm

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3
Q

This zone of mesoderm is a thin plate lateral to the intermediate mesoderm. It splits to form the lining of body cavities and mesoderm of most internal organs as well as limbs.

A

Lateral plate mesoderm

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4
Q

Remember that mesoderm originates from _______, passes through the primitive streak as _______ cells, spreads laterally, and establishes a continuous layer between ectoderm and endoderm.

A

Epiblast

Bottle

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5
Q

________ are initial pairs of segments of mesenchyme (barely discernible as segments) that begin to develop along and on either side of the neural plate in the paraxial mesoderm.

A

Somitomeres

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6
Q

New somitomeres are added (CRANIALLY/CAUDALLY) as the primitive steak regresses.

A

Caudally

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7
Q

After 20 pairs of somitomeres have formed (about day 20), the first pair of somites forms behind (caudal to) the ____ pair of somitomeres at the expense of the ____ pair of somitomeres.

A

7th

8th

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8
Q

________ are more dense, blocks of mesoderm that form along the notochord.

A

Somites

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9
Q

In a caudal direction, a pair of somitomeres is transformed into a pair of _______ every few hours.

A

Somites

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10
Q

As pairs of somites are formed, pairs of somitomeres are also formed at the (ANTERIOR/POSTERIOR) end of the primitive node.

A

Anterior

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11
Q

For each pair of somitomeres transformed into a pair of somites, a new pair of somitomeres is formed at the caudal end of the paraxial mesoderm. Because of this transformation and the formation of somites, _____ pairs of somitomeres are kept constant at the caudal end of the paraxial mesoderm.

A

11

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12
Q

Cells migrating through the primitive streak will form…

A

Cervical vertebrae
Thoracic vertebrae
Lumbar vertebrae

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13
Q

Cells migrating from the tail bud will form the…

A

Sacrum

Coccyx

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14
Q

There are ____ cranial somitomeres that will form most of the skeletal musculature of the head.

A

7

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15
Q

The history of a somite includes the following stages:

1) _______ stage
2) Epitheliomesenchymal transformation stage
3) Separation of _______
4) Breakup of epithelial dermatome into dermal _______

A

Epithelial
Myotome
Fibroblasts

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16
Q

In somite differentiation, this mechanism utilizes FGF-8, retinoic acid, and Mesp-2.

A

Wavefront mechanism

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17
Q

In the wavefront mechanism, increased _____ initiates mitosis in mesenchymal cells in the posterior primitive streak.

A

FGF-8

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18
Q

In the wavefront mechanism, increased ______ ______ more anteriorly opposes the action of FGF-8.

A

Retinoic acid

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19
Q

Note that the wavefront is also referred to as the determination front because there is a balance between FGF-8 and retinoic acid concentrations that results in cellular determination toward somitogenesis. ______ is important at this critical decision moment and is expressed because of the specific balance between FGF-8 and retinoic acid concentrations.

A

Mesp-2

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20
Q

This is the mechanism in somite differentiation that involves the roles oscillating expression of molecules in the Notch pathway (along with Wnt and FGF pathways) that leads to the establishment of the pattern for somite formation. This is expressed along a time line.

A

Segmentation clock

21
Q

At each critical location that will serve to divide adjacent somites, ______ ______ will become concentrated at the future anterior border of a somite and ______ will be concentrated at the future posterior border of a somite.

A

Lunatic fringe

C-hairy

22
Q

Cells at the anterior border of a somite express _____ (receptor) and cells of the posterior border of the anterior somite will express _____ (ligand), resulting in a fissure between the two adjacent somites.

A

Eph A

Eph B

23
Q

Overlying ectoderm causes the expression of _____, which in turn causes the expression of ______ in the forming somite.

A

Wnt-6

Paraxis

24
Q

_______ plus the down regulation of _______ results in the conversion of mesenchymal cells to epithelial cells. Then the somitocoel forms.

A

Paraxis

Snail

25
Q

The notochord expresses _____ and ______, which responds by then expressing ______ and ______ in the ventral half of the somite, which is now called the sclerotome.

A

Shh
Noggin
Pax1
Pax9

26
Q

Under the influence of secreted products of _____ genes produced by the dorsal neural tube and the surface ectoderm, the dorsal half of the epithelial somite becomes transformed into the __________.

A

Wnt

Dermomyotome

27
Q

The dermomyotome expresses _____, _____, and _____. The expression of these results in the separation of the dermomyotome into dorsal dermatome and ventral myotome.

A

Pax3
Pax7
Paraxis

28
Q

The __________ is the dorso-lateral part of a somite.

A

Dermomyotome

29
Q

_____ signaling from the notochord and _____ signaling from the dorsal neural tube create a balance that causes the myotome portion to commit to the myogenic lineage.

A

Shh

Wnt

30
Q

______ is produced by the lateral plate which suppresses myogenesis in the ventrolateral dermomyotome and stimulates cells from this area to migrate from the somite into the limb bud.

A

BMP-4

31
Q

_______ inhibits BMP-4, which would normally inhibit myogenesis.

A

Noggin

32
Q

FGF from the myotome signals the sclerotome to produce _______, which causes the anterior and posterior borders of each somite to form the syndetome which is the precursor of tendons.

A

Scleraxis

33
Q

Sclerotomal portion of each somite breaks up into an anterior and a posterior portion. The (ANTERIOR/POSTERIOR) portions of one somite joins the (ANTERIOR/POSTERIOR) portion of the somite caudal to it to form the body of a vertebra.

A

Posterior

Anterior

34
Q

The joining of a posterior and anterior portion of somites creates gaps that allow _______ to grow out from the neural tube into the epaxial segmental musculature derived from the myotomes.

A

Nerves

35
Q

The future intermediate mesoderm responds to _____ (from lateral ectoderm) and ______ (from paraxial mesoderm) and becomes intermediate mesoderm and expresses ______.

A

BMP
Activin
Pax-2

36
Q

Intermediate mesoderm is associated with the formation of the ________ and, later, the ________.

A

Pronephros

Mesonephros

37
Q

Cranial and caudal extent of the intermediate mesoderm is dependent on expression of ______ and ______.

A

Hox-4

Hox-11

38
Q

In the chick embryo 24 hour xs, the cardiac tube contains the…

A

Myocardium

Endocardium

39
Q

Early heart-forming cells arise in the _______ and migrate through the primitive streak.

A

Epiblast

40
Q

Heart-forming cells migrating through the anterior primitive streak form the…

A

Outflow tract

41
Q

Heart-forming cells migrating through the middle of the primitive streak form the…

A

Ventricles

42
Q

Heart-forming cells entering the primitive streak mostly posteriorly form the…

A

Atria

43
Q

All of the cells going through the primitive streak lead to the formation of the ______ ______.

A

Cardiac crescent

44
Q

In early heart formation, the anterior visceral endoderm expresses the signaling molecules _____ and _____. These help form the cardiac crescent.

A

BMPs

FGFs

45
Q

Once formed, the cardiac crescent expresses the genes ______, ______, and ______. The expression of these genes form transcription factors necessary for early heart formation.

A

Nkx2-5
MEF2
GATA4

46
Q

These are bilaterally paired tubes that form from the cardiogenic mesoderm that eventually fuse beneath the foregut to form a single tube.

A

Cardiac tubes

47
Q

Each cardiac tube consists of an outer layer and inner layer. The outer layer will form (ENDOCARDIUM/MYOCARDIUM) and the inner layer will form (ENDOCARDIUM/MYOCARDIUM).

A

Myocardium

Endocardium

48
Q

Cardiac ______ forms between the two layers of the cardiac tubes. It contains a specialized extracellular matrix.

A

Jelly

49
Q

This is the source of the pericardium and myocardial fibroblasts.

A

Proepicardial primordium

Embryology (11 decks)

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