embryonic development

Embryonic Development (mosly mice and mammals)

Chapter 10

Cleavage

Cell division without growth

First few divisionsare slow (24 hrs, then12 hrs)

Blastomeres

Products of cleavage

Compaction

Developing embryobecomes more spherical.

Flattening of blastomeresto form to maximize

intracellular contacts.

Microvilli

Cell membrane protrusions

and Gap Junctions

Cellular connectionsjoining cell cytoplasms

form

Porter, Fonte and Weiss, Cancer Research, 1974

Microvilli

Figure 20-22 Essential Cell Biology (© Garland Science 2010)

Gap Junctions

connexon proteins

Morula

Embryo from compactionto about the 32-cell stage

Desmosomesand tight junctionsform

Desmosomes

Localized, spot-like,cell-to-cell adhesions

Figure 17-2a Essential Cell Biology (© Garland Science 2010)

Figure 17-2b Essential Cell Biology (© Garland Science 2010)

Tight Junctions

Junctions sealing neighboring cells together

so that water-soluble moleculescannot easily leak between them

Figure 20-23a, b Essential Cell Biology (© Garland Science 2010)

Figure 20-23c Essential Cell Biology (© Garland Science 2010)

Blastocoel

Fluid-filled cavity

begins to form, forming...

the Blastocyst

Mammalian embryo after cavitation

the Blastocyst,

Mammalian embryo after cavitation

consisting of the Trophoectoderm, Blastocoel and Inner Cell Mass

Trophoectoderm

The outer layer of the blastocyst,which will form part of

the placenta

Inner Cell Mass

Will form the “embryo proper”and the amnion

Amnion

Extraembryonic membraneenclosing the embryo

ICM and trophoectoblastcells become determined

Late Blastocyst

Formation ofdistinct regions

Implantation

Emergence from the zona

Attachment to the uterine wall

Initial formation of the placenta

“Hatching”

Emergence from the zona; trophoectoderm cells

opposite the ICM secrete a protease

that digest the zona

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