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Unit 7: MCP > Embryogenesis (7) > Flashcards

Embryogenesis (7) Flashcards

1
Q

When does embryogenesis occur?

A

Weeks 1-8 of human pregnancy

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2
Q

Generally speaking, what occurs during embryogenesis?

A

Organ primordia is established

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3
Q

Where is the oocyte fertilized?

A

In the ampullary region of the uterine tube

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4
Q

What is the order of cleavage divisions?

A 
Zygote
2 cell
4 cell
8 cell
Morula
Blasocyst
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5
Q

When is the blastocyst formed?

A

By the end of the 1st week of pregnancy…it begins to implant into the uterine wall

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6
Q

What does fertilization result in?

A

A diploid zygote

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7
Q

What do cleavage divisions do to the size of the cells and the number of cells?

A

Decrease size

Increase number

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8
Q

What happens after the third cleavage division?

A

Blastomeres maximize their contact with each other to form a compact ball of cells (compaction)

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9
Q

What does compaction do to the cells?

A

Segregates inner cells from outer cells

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10
Q

When is the morula formed?

A

About 3 days after fertilization?

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11
Q

How many cells are present in the morula?

A

16 cells

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12
Q

When does each of the following appear after fertilization:

2 cell
4 cell
16 cell
Late morula

A

2 cell: 30 hours

4 cell: 40 hours

16 cell: 3 days

Late morula: 4 days

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13
Q

What are the components of the blastocyst?

A

Inner cell mass (ICM) and Outer cells and Blastocoel

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14
Q

What does the ICM give rise to?

A

Tissues in the embryo proper

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15
Q

What doe the outer cells of the blastocyst give rise to?

A

The trophoblast that later contributes to the placent

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16
Q

How is the blastocoel formed?

A

Fluid penetrates the ICM

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17
Q

What type of cells are ICM cells?

A

Pluripotent stem cells

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18
Q

What do trophoblast cells attach to and how?

A

Attach to the uterine wall epithelium. They penetrate between the epithelial cells of the uterine mucosa (endometrium)

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19
Q

What are L-selectins?

A

Carbohydrate binding proteins on the trophoblast cells. They interact with carbohydrate receptors on the uterine epithelium and mediate attachment

20
Q

What happens in trophoblast differentiation?

A

2 layers are formed.

Cytotrophoblast: inner layer of mononucleated cells

Synchtiotrophoblast: Outer multinucleated layer that lacks distinct cell bondaries

21
Q

Which layer of the trophoblast continues to expand into the uterine wall?

A

Syncytiotrophoblast

22
Q

What does the ICM differentiate into? When does this occur?

A

Hypoblast and epiblast. Together these form a flat bilaminar disc.

Occurs at day 9.

23
Q

What forms within the epiblast?

A

Amniotic cavity

24
Q

Where do embryonic tissues arise from?

A

Epiblast layer if ICM

25
Q

What does gastrulation achieve?

A

3 germ layers

26
Q

What are the goals of gastrulation?

A

1- Bring inside the embryo areas destined to form endodermal organs

2- Surround the embryo with cells capable of forming ectoderm

3- Place mesodermal cells in proper positions inbetween

27
Q

When does gastrulation occur? And what does it begin with?

A

Week 3

Begins with formation of the primitive streak.

28
Q

What is invagination?

A

The epiblast cells migrate into the primitive streak after detaching from the epiblast. They move through the streak and slip beneath it

29
Q

What does invagination give rise to?

A

Endoderm and mesoderm.

Some cells displace the hypoblast and create endoderm

Some cells lie between epiblast and new endoderm and create mesoderm.

30
Q

After invagination occurs…what do cells remaining in the epiblast form?

A

The ectoderm

31
Q

What does the ectoderm lead to?

A

Outer surface, CNS, Neural crest

32
Q

What does the mesoderm lead to?

A

Muscle, skeletal system, circulatory system

33
Q

What does the endoderm lead to?

A

Digestive tube, pharyxn, respiratory tube, other internal organs

34
Q

What is neurulation?

A

Process of neural tube formation

35
Q

What are the steps of neurulation?

A 
1- Formation
2- Folding
3- Elevation of neural crest
4- Convergence
5- Closure
36
Q

What does neurulation divide the neural ectoderm into?

A

3 distinct domains:

Neural tube
Neural crest
Surface ectoderm

37
Q

What do the retina and CNS develop from?

A

Neural tube

38
Q

What do the PNS, teeth, melanocytes and facial cartilage develop from?

A

Neural crest

39
Q

How many site of neural tube closure is there and how does closure proceed?

A

3 sites of closure and fusion occurs bidirectionally

40
Q

What is failure of posterior neural tube closure?

A

Spina bifida

41
Q

What is failure of anterior neural tube closure?

A

Anacephaly

42
Q

What is complete failure of neural tube closure?

A

Craniorachischisis

43
Q

Where does theneural crest cell transition from epithelium to mesenchymal occur?

A

At the dorsal neural tube (and then after they give rise to tissues)

44
Q

What are the regions of neural crest cells?

A

Cranial (cephalic) neural crest

Cardiac neural crest

Trunk neural crest

Enteric (vagal and sacral) neural crest

45
Q

True or False: Neural crest cells follow distinct migration patterns.

A

True

Unit 7: MCP (16 decks)

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