Undifferentiated Cells

EmbryogenesisStem Cells

Embryogenesis

• The formation of an embryo• The development a new individual

from a zygote

Embryogenesis Summary

Germ cells

Zygote Morula Blastula Blastocyst Gastrula

Fertilization BlastulationCleavage Gastrulation

Hatching & Implantation

Embryogenesis

http://www.mymcat.com/wiki/Embryogenesis

blastocyst

-Tight junction-Outcome of mitosis-2n

Ferlization Mitosis

- Solid mass of cells

Blastulation

-Hollow mass of cells

Embryogenesis: Fertilization

• Germ cells / sex cells:– sperm, ovum– Haploid (1 copy of each chromosome,

half the genetic information)• Zygote: fertilized egg– Diploid (2 copies of each chromosome)

http://www.mymcat.com/wiki/Embryogenesis

Blastocyst

• Differentiation begins in the blastocyst

• Inner cell mass: becomes the embryo and some extraembryonic tissue

• (Outer) Trophoplast: becomes the placenta

http://www.kumc.edu/images/stemcell/looklike.jpg

https://ehumanbiofield.wikispaces.com/file/view/rem2s2_1.jpg/31809601/rem2s2_1.jpg

Zona pellucida

Embryogenesis

http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea2.jpg

Embryogenesis: Gastrulation

• Gastrula is composed of 3 germ layers:– Outer: Ectoderm–Middle: Mesoderm– Inner: Endoderm

http://www.mymcat.com/wiki/Embryogenesis

Embryogenesis: Gastrulation

3 germ layers will eventually differentiate into• Ectoderm: epidermis, nervous system• Mesoderm: muscle, bone, blood, urinary tract• Endoderm: GI tract, lungs

Video: The first 9 weeks of pregnancy

http://www.babycenter.ca/video/pregnancy/weeks-1-to-9-pregnancy/

http://i-newnews.com/wp-content/uploads/2012/01/3060_3083_31.jpg

Embryogenesis Summarized

Germ cells

Zygote Morula Blastula Blastocyst Gastrula

Embryonic Stem Cell (ESC)

PluripotentTotipotent

Fertilization BlastulationCleavage Gastrulation

Hatching & Implantation

Stem Cells

• Unspecialized / undifferentiated cell

• Has the potential of becoming a specialized cell with a specific function

• Property of self-renew for long periods of time (immortal)

• Formed during the development of the embryo

Stem cell division. A – stem cellsB – progenitor cellC – differentiated cell

Types of Stem Cells

• Embryonic stem cells– Stem cells taken from the pre-

implantation stage of the embryo– Totipotent or pluripotent

• Somatic / Tissue / Adult stem cells– Exist within specialized tissue– Able to differentiate into certain types of

cells –Multipotent

Proliferative Potential: Potency

• A cell’s potential to differentiate

• Levels of potency:– Totipotent– Pluripotent–Multipotent– Unipotent– Terminally

differentiated

Totipotent

• Capable of giving rise to any and all cell types– Somatic cells– Germ cells– Placenta

• Can form a whole organism / embryo• Totipotent cells: zygote, morula

Pluripotent

• Capable of giving rise to many cell types– Somatic cells– Germ cells

• Can not develop into an organism because incapable of producing extraembryonic tissue – placenta

• Pluripotent cells: blastocyst (inner cell mass)

Multipotent

• Also known as progenitor cells • Can give rise to multiple, but limited

number of lineages• Committed to produce specific cell

types and thus specialization potential is limited to one or more cell lines

• Adult / tissue stem cells: found in the tissues of adult mammals

Unipotent

• Capable of differentiating into one cell type

Terminally Differentiated

• Cells that are unable to divide

• Example: neurons, adipocyte, cardiomyocyte, skeletal muscle cells, skin cells

Stem cell division. A – stem cells; B – progenitor cell; C – differentiated cell; 1 – symmetric stem cell division; 2 – asymmetric stem cell division; 3 – progenitor division; 4 – terminal differentiation

http://en.wikipedia.org/wiki/File:Stem_cell_division_and_differentiation.svghttp://www.ncbi.nlm.nih.gov/books/NBK6180/