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Ortho/Pedo > More Embryological Development > Flashcards

More Embryological Development Flashcards

1
Q

What important features are included for cleavage?

A
  1. Subdivides zygote without increasing its size
  2. Starts at the 8-cell stage
  3. Blastomeres flatten and develop polarity
  4. Outer surfaces of cells becomes convex and inner surfaces becomes concave
  5. With compaction, some blasatomeres segregate to the center of the morula and others to the outside
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2
Q

What is a blastomere?

A

A cell formed by cleavage of a fertilized ovum.

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3
Q

What is a morula?

A

A solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.

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4
Q

What is a blastocyst?

A

An embryo at the early stage of development when it is a hollow ball of cells. Develops from a morula. Consists of cells forming an outer trophoblast layer, an inner cell mass and a fluid-filled cavity

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5
Q

What is a gastrula

A

an embryo at the stage following the blastocyst, when it is a hollow cup-shaped structure having THREE layers of cells.

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6
Q

Preimplantation genetic diagnosis PGD can be performed using:

A

Blastomeres

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7
Q

What types of patients is PGD usually performed on?

A

Those with increased age, and/or a high risk of transmitting a disease (causing mutation.)

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8
Q

What is a trophoblast?

A

A peripheral outer cell mass, which is the main source of the placenta

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9
Q

What is the embryoblast?

A

A inner cell mass which gives rise to the embryo proper

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10
Q

The cleaving embryo differentiates into what two groups of cells?

A

Trophoblasts and embryoblasts

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11
Q

During cleavage, the trophoblast cells express what?

A

A basally polarized membrane sodium/ potassium ATPase

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12
Q

The sodium/ potassium ATPase pumps_________ into the interior of the morula. And water follows trough osmosis to become ____________.

A

Sodium

Blastocoelic fluid.

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13
Q

The side of the blastocyst containing the inner cell mass is called the _____________ and the opposite side is called the_____________.

A

embryonic pole

abembryonic pole

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14
Q

What happens during zona hatching?

A

The zona pellucida degenerates and decomposes and is replaced by the underlying layer of the trophoblast cells now called the cytotrophoblast

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15
Q

What is the syncytiotrophoblast?

A

a mass of cytoplasm containing numerous dispersed nuclei which begin to implant the blastocyst into the uterine wall.

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16
Q

What happens during the second week of development?

A

The embryoblast splits into two layers forming a bilaminar embryonic disc.

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17
Q

What are the two layers of a bilaminar embryonic disc?

A
  • The epiblast or primary ectoderm

- The hypoblast or primary endoderm

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18
Q

As implantation progresses, the syncytiotrophoblast (expands/shrinks)

A

Expands

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19
Q

On what day does the amniotic cavity appear?

A

8

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20
Q

What do the cells of the bilaminar germ disc develop into?

A

The embryo proper

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21
Q

What two things does the a bilaminar germ disc lie between?

A

amniotic cavity and the blastocyst cavity

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22
Q

What is the coagulation plug?

A

A plug of acellular material that seals the small hole where the blastocyst implanted.

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23
Q

What does the hypoblast form on day 9?

A

The extraembryonic endoderm

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24
Q

What does the extraembryonic endoderm do?

A

Completely lines the former blastocyst cavity and this membrane is now called Heuser’s membrane

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25
Q

What does the extraembryonic mesoderm do?

A

fills in-between Heuser’s membrane and the cytothrophoblast, with loosely arranged cells.

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26
Q

Once Heuser’s membrane is formed the blastocyst cavity is now called what?

A

Primary yolk sack

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27
Q

What happens on day 11-13?

A

cytotrophoblastic lacunae begin to anatstomose with maternal capillaries and become filled with blood.

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28
Q

What happens between days 12 and 13?

A

A new space called the extraembryonic coelom or chorionic cavity forms by splitting of the extraembryonic mesoderm into two layers.

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29
Q

What does the extraembryonic coelom do?

A

It separates the embryo with its attached amnion and yolk sac from the outer wall of the blastocyst.

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30
Q

What happens as the definitive yolk sac develops?

A

The primary yolk sac breaks up and is reduced to a collection of vesicles

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31
Q

What does the hypoblast produce on day 12?

A

A new membrane that migrates out over the inside of the extraembryonic mesoderm and pushes the yolk sac in front of it.
This new layer becomes the endodermal lining of the definitive yolk sac

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32
Q

What is suspended in the chorionic cavity by the end of the second week?

A

The definitive yolk sac, and the bilaminar germ disc with its dorsal amnion and ventral yolk sac.

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33
Q

What happens during the third week?

A

The appearance of a faint midline structure called the primitive streak in the epiblast.

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34
Q

What is pseudopodia?

A

When flattened epiblast cells develop long, foot like processes, which allow them to migrate through the primitive streak into the space between the epiblast and the hypoblast

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35
Q

What is gastrulation?

A

Cell migration, invagination and ingress

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36
Q

What happens to epiblast cells on day 16?

A

They begin to proliferate, flatten and lose their connections with each other

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37
Q

What is the definitive endoderm?

A

A new layer of cells formed when the ingressing epiblast cells invade the hypoblast and displaces (and eventually replaces) its cells

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38
Q

What does the definitive endoderm give rise to?

A

the gut and gut derivatives

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39
Q

What is the intraembryonic mesoderm?

A

A third germ layer formed when some of the epiblast cells migrating through the primitive streak diverge into the space between the epiblast and the definitive endoderm.

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40
Q

The intraembryonic mesoderm cells that migrate laterally begin to organize into what?

A

somitomeres

41
Q

On day 17, a tube of intraembryonic mesodermal cells migrates cranially from the primitive node and forms what two things?

A

notochordal process (is hollow) and the prechordal plate.

42
Q

The prechordal plate is a (thickening/ thinning) in the endodermal level.

A

Thickening

43
Q

How is the prechordal plate formed?

A

intraembryonic mesendermal cells from the primitive node that migrate cranially along the midline between the ectoderm and endoderm layers.

44
Q

Once the ingressing of the epiblast cells is complete, the epiblast layer is called the _____________ and the Bilaminar germ disc is now____________.

A

Ectoderm

Trilaminar

45
Q

The prechordal plate gives rise to what?

A

the endodermal layer of the oropharyngeal membrane, which forms the mouth opening, and participates in the patterning of the cranial neural tube.

46
Q

During the third week, what appears in the ectoderm?

A

two faint depressions: one at the cranial end and one at the caudal

47
Q

Late in the third week, the ectoderm fuses with what, forming what?

A

underlying endoderm, bilaminar membrane

48
Q

What is the cranial membrane called?

A

buccopharyngeal membrane

49
Q

What is the claudal membrane called?

A

cloacal membrane

50
Q

As gastrulation proceeds, what regresses cranially to caudally?

A

primitive streak

51
Q

By what day does the primitive streak disappear?

A

Day 26

52
Q

What does the primitive streak leave behind after is disappears?

A

a caudal midline mass of mesoderm behind called the caudal eminence

53
Q

What does the notochordal process do?

A

elongates and parallels the regression of the primitive streak.

54
Q

When is the notochordal process formation complete?

A

Day 20

55
Q

At 21 days (3 weeks), the embryos cranial and caudal portions of the paraxial mesoderm have become organized into what?

A

somitomeres

56
Q

Somitomeres will later develop into what?

A

skeletal muscle, tendons, cartilage and bone

57
Q

Between days 16 – 22 the hollow notochordal process begins to fuse with the underlying endoderm forming what?

A

notochordal plate

58
Q

The notochordal plate disengages with the endoderm to form what?

A

solid notochord

59
Q

How does the neural plate appear?

A

as a thickening in the ectoderm on either side of the midline, cranial to the primitive node

60
Q

What does the neural plate consist of?

A

a broad cranial portion that will give rise to the brain and a narrow caudal portion that will give rise to the spinal cord.

61
Q

What is neurulation?

A

a process of folding along the neural groove

62
Q

What does neurulation do?

A

converts the neural plate to a hollow neural tube, which sinks into the body wall and begins to differentiate into the brain and spinal cord.

63
Q

Bending of the neural plate involves formation of what?

A

neural folds at the lateral edges of the neural plate

64
Q

What do neural folds consists of?

A

neuroepithelium (specialized epithelium which form the central nervous system) and adjacent surface ectoderm.

65
Q

The neural plate begins to crease ventrally along its midline called what?

A

neural groove

66
Q

What do the neural folds do to form he neural tube and neural canal?

A

elevate, rotate dorsally and fuse

67
Q

Closure of the neural groove involves what?

A

the adhesion of the neural folds to one another and the subsequent rearrangement of cells within the folds to form two separate epithelial layers.

68
Q

Where do neural crest cells form?

A

in the interface between epithelial layers

69
Q

As neurulation occurs, the neural crest cells detach from the neural tube and undergo what?

A

an epithelial to mesenchymal transformation

70
Q

The route that particular neural crest cells take and where they stop migrating along this route, determines what?

A

What type of cell they will form

71
Q

After neural crest cells have separated form the neural tube they begin extensive migration where?

A

beneath the surface ectoderm

72
Q

Migration of neural crest cells is so extensive it could almost be considered what?

A

a fourth primary germ layer

73
Q

What involves adhesion of the neural folds to one another?

A

Closure of the neural groove

74
Q

Closure of the neural groove begins where?

A

at the occipitocervical region

75
Q

Closure of the neural grooves leaves what open at the cranial and caudal ends?

A

neuropores

76
Q

(T/F) The neural tube lengthens as it zips up both cranially and caudally

A

True

77
Q

What is the last thing to close, finishing the closure of the neural grooves?

A

the anterior and posterior ends (neuropores)

78
Q

Then, the neural tube is covered dorsally by what?

A

mesenchyme

79
Q

The mesenchyme forms into what?

A

vertebral arches and skull

80
Q

At the end of the third week, the embryo is a what?

A

flat Ovoid, trilaminar disc.

81
Q

During the fourth week the embryo grows rapidly, particularly in what?

A

Length

82
Q

During the fourth week the embryo goes through what process?

A

Folding

83
Q

The main force responsible for embryonic folding is what?

A

the differential growth of various embryonic structures.

84
Q

The embryonic disc and amnion grow (quickly/ slowly) but the yolk sac grows (hardly at all/ a lot)

A

quickly, hardly at all

85
Q

What three things stiffen the dorsal axis of the embryo?

A

notochord, neural tube and somites

86
Q

Most of the embryonic folding happens where?

A

the thin, flexible outer rim of the disc.

87
Q

Since the embryo grows faster in length than in width, these reflections are (deeper/ shallower) at the caudal and cranial end, than along the sides

A

Deeper

88
Q

The cranial rim of the embryonic disc contains what?

A

the oropharyngeal membrane

89
Q

The horseshoe-shaped cardiogenic area, will give rise to what?

A

The heart <3

90
Q

Where does the septum transversum form?

A

Cranial to the cardiogenic area

91
Q

The septum transversum forms the initial partition separating the coelom into what?

A

thoracic and abdominal cavities

92
Q

The septum transversum gives rise to what?

A

part of the diaphragm, stomach and duodenum.

93
Q

At the head and tail ends of the embryo, lateral edges of the embryonic disc make contact with each other and then zip up toward the site of the future what?

A

umbilicus

94
Q

When does an encephalocele occurs, and what is it?

A

occurs early in a woman’s pregnancy when part of the developing baby’s skull doesn’t close completely.

95
Q

If encephalocele occurs in the cranial region, and a pouch of brain and meniges bulge from the occiput, it is called an

A

meningoencephalocele

96
Q

If brain tissue protrudes as well as a ventricular cistern (CSF filled spaces) it is called:

A

Meningohydroencephalocele

97
Q

What is spina bifida?

A

a set of malformations of the spinal cord caused by failure of closure of the neural tube and lack of fusion of the vertebral arches, soft tissues, and skin that cover the back.

98
Q

What are the three types of spina bifida?

A

Myelomeningocele, meningocele, Spina Bifida Occulta

Ortho/Pedo (6 decks)

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