Lect 7: Embryogenesis Flashcards Preview

Unit 7 - MCP > Lect 7: Embryogenesis > Flashcards

Flashcards in Lect 7: Embryogenesis Deck (35):
1

Cleavage Divisions

reduce the size of the cells but increase the number of cells.

2

During cleavage divisions the cells are known as

blastomeres

3

after he 3rd cleavage, blastomeres maximize their contact with each other and form a compact ball of cells.

compaction (8-cell). It segregates inner cells from outer cells.

4

Around 3 days after fertilization, the compacted embryo divides to form a 16-cell

morula (16-cell).

5

ICM - Inner Cell Mass

these are the inner cells of the morula. - this ICM gives rise to the embryo proper

6

The OCs give rise to the

trophoblast that later contributes to the placenta. Fluid then penetrates into the intercellular spaces of the ICM to form the blastocoel (fluid filled cavity). At this time the embryo is a BLASTOCYST

7

Which cell type is the source of embryonic cells?

ICM - they are pluripotent (they can differentiate into any cell type in the body. They are the ones that latch onto the uterine wall, while the trophoblast will b the surrounding cells

8

Trophoblast will gives rise to

extraembryonic cells - placenta etc

9

Totipotent cells

can give rise to extraembryonic and all cell types in body

10

Trophoblast cells penetrate between epithelial cells of the uterine via which molecule

L-selectins

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Next Step: Trophoblast differentiates into two layers -cytotrophoblast and synctiotrophoblast. Synctiotrophoblast expands into the uterus and lose the cellular morphology multinucleate .

Syctiotrophoblas begin to to invade the epithelium and expands into uterus.

12

DAY 9. ICM splits into 2 layers 1hypoblast and epiblast.

Together they form a flat bilaminar disc.

The amniotic cavity forms within the epiblast.

The trophoblast invades maternal capillaries to establish uteroplacental citculation

13

Summary thus far

Fertilization results in the formation of a diploid zygote and
activates cleavage division.
• Compaction forms a tight ball of cells that separate into inner
and outer layers. The inner cell mass (ICM) will give rise to the
embryo proper and the outer cells will form the trophoblast.
• Implantation occurs at the end of the first week, when
trophoblast cells invade the uterine wall epithelium.
• The trophoblast differentiates into cytotrophoblast and
syncytiotrophoblast that contribute to extraembryonic tissues.
• ICM differentiates into epiblast and hypoblast to form a bilaminar
disc.

14

Gastrulation

wk 3: gastrulation establishes the three germ layers. it begins witht the primitive streak on the surface of the epiblast. The primitive streak becomes a narrow groove with a structutre called the primitive node surrounding primitive pit at the cephalic end

15

Next in granulation

epiblasts mograte toward the primitive streak and then detach from the epiblast and move through the primitive streak to slip beneath it...inward movement is called invagination. Cells move inside the primitive streak toward the primitive node transforming a two-cell to ta three-cell.

16

Next in gastrulation (2)

Once the cells hv invaginate, some displace the hypoblast to create the endoderm. Other invaginating cells lie between the epiblast and the new endoderm to form the mesoderm layer. Cells remaining in the epiblast form the ectoderm

17

What is the primary driver?

the primitive node

18

The Anterior Visceral Endoderm (AVE)

have genes for forming the head - the anterior side

19

BMP -4 makes which side?

ventral side

20

Summary again

During gastrulation extensive cell movements and
rearrangements of the bilaminar disc establish three germ layers
(ectoderm, mesoderm, endoderm).
• Epiblast cells invaginate through the primitive streak to form
endoderm and mesoderm.
• Epiblast cells give rise to all three germ layers, and therefore all
body tissues.
• Ectoderm, mesoderm and endoderm give rise to specific cell
types and body tissues.
• Body axes are established before or during gastrulation.

21

Neuralation

the process by which the neural plate forms the neural tube

22

Neurulation divides the ectoderm into three distinct domains

1. Surface epithelium (epidermis)
2. Neural crest
3. Neural tube - will form the brain and spine

23

Failure of closure of the posterior neurophore results in

spina bifida

24

Failure of closure of the anterior neurophore results in

anencephaly

25

NTD prevented if mom takes folic acid

acid

26

Neural crest cells give rise to mesoderm and ectoderm

The neural crest cells arising from the margins of the neural tube. These cells migrate to many different locations and differentiate into many cell types (heart, neural, skin, teeth, face etc) within the embryo.

27

Neural Crest undergo an Epithelial-to-Mesenchymal transition

at the dorsal neural tube and then migrate to give rise to tissues. (Mesenchyme is loosely organized conn tissue of any origin)

28

NC cells migrate to different tissues:

cranial, cardiac, Trunk and Enteric NC

29

Cardiac NC enter the outflow tract of the heart

to generate the septum between the great arteries

30

Summary 3.

During gastrulation extensive cell movements and
rearrangements of the bilaminar disc establish three germ layers
(ectoderm, mesoderm, endoderm).
• Epiblast cells invaginate through the primitive streak to form
endoderm and mesoderm.
• Epiblast cells give rise to all three germ layers, and therefore all
body tissues.
• Ectoderm, mesoderm and endoderm give rise to specific cell
types and body tissues.
• Body axes are established before or during gastrulation

31

Q1. The second week of embryogenesis can be regarded as the week of 2s. The formation of what structures supports this idea?

1. The trophoblast differentiates to form 1. cytotrophoblast and synctiotrophoblast
2. The ICM forms the hypolast and the epiblast

32

Q2. What is gastrulation?

epiblast gives rise to endoderm, ectoderm and mesoderm

33

Q.3 Where do ES come from?

inner cell mass

34

Implantataion of the blastocyst occurs when?

one week post fertilization

35

Cardiac neural crest cells migrate into the heart to contribute to?

the septum of the outflow tract that separates the aorta and pulmonary artery.