Differentiation
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Transcript of Differentiation
EmbryogenesisPotency
Stem CellsSpecialized Cells
Cellular Differentiation
Cellular Differentiation
Process of producing specialized cellsSpecialized cells have physical and
chemical differences that allow them to perform a function that is different than other cells
All specialized cells come from pre-existing cells so there must be a starter cell that is unspecialized
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
Embryogenesis
The formation of an embryoThe development a new individual
from a zygote
Embryo
A fertilized egg in the early stages of development before hatching
In humans, it is defined as the period from fertilization to the end of the first 8 weeks of pregnancy
From conception, to implantation, but before organ formation
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
Embryogenesis: Cleavage
Morula: a solid mass of cells Usually defined after the 8-cell stageFormation of tight junctions
Proteins that join 2 cell membranes together to form an impermeable barrier to fluid
Deforms the round shape of the cells
http://www.mymcat.com/wiki/Embryogenesis
Embryogenesis: Blastulation
Forming the blastula by cell division from the morula
Blastula: a hollow mass of cells In humans, the blastula develops into
the blastocyst
http://www.mymcat.com/wiki/Embryogenesis
blastocyst
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
Hatching
Throughout all these stages (zygote, morula, blastula, blastocyst), the embryo has been encased in a sac called the zona pellucida
At this point, the embryo will hatch from the zona pellucida to begin implantation in the uterus
http://www.vivo.colostate.edu/hbooks/pathphys/reprod/fert/cleavage.html
Embryogenesis
http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea2.jpg
https://ehumanbiofield.wikispaces.com/file/view/rem2s2_1.jpg/31809601/rem2s2_1.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
Embryogenesis
http://www.mymcat.com/wiki/Embryogenesis
Embryogenesis
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Embryogenesis
A. Unfertilized eggB. 8-cell stageC. 16-cell stageD. 32-cell stageE. MorulaF. Early blastulaG. Unhatched blastulaH. Hatched blastula,
vegetal pole view
I. Hatched blastulaJ. Early mesenchyme
blastulaK. Late mesenchyme
blastulaL. Early gastrulaM. Mid gastrulaN. Late gastrula
http://ars.sciencedirect.com/content/image/1-s2.0-S1567133X05001250-gr3.jpg
Video: The first 9 weeks of pregnancyhttp://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
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 / embryoTotipotent 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
Embryogenesis Summarized
Germ cells
Zygote Morula Blastula Blastocyst Gastrula
Embryonic Stem Cell (ESC)
PluripotentTotipotent
Fertilization BlastulationCleavage Gastrulation
Hatching & Implantation
Multipotent
Also known as progenitor cells Can give rise to multiple, but limited
number of lineagesCommitted 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
Types of Adult Stem Cells
Lineage Differentiated cells
Haematopoietic
RBC, WBC, platelets etc.
Intestinal Cells on lining of large and small intestine
Neural Astrocyte, oligodendrocytes, neurons
Mesenchymal
bone, cartilage, fat, cells that support the formation of blood, and fibrous connective tissue
Endothelial Endothelial tissue that line the walls of blood and lymphatic vessels
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/
Location of Stem Cells
Comparing Potency
Potency Type of stem cell
Location of cells
Totipotent Embryonic stem cell
Zygote, morula
Pluripotent
Embryonic stem cell
Blastocyst
Multipotent
Adult / Tissue / Somatic stem cell
In various tissues
The “typical” animal cell
Fig. 7.7 Campbell
The “typical” plant cell
Fig. 7.8 Campbell
What actual cells look like
Cells in organisms are specializedDifferentiation not only affects
function but also STRUCTURECells physically look different from
each other
Specialized Cells
Complex organisms contain many different types of cells that perform different functions
Specialized cells have physical and chemical differences that allow them to perform one job very well
Specialized Plant Cells:transport cells (xylem in orange, phloem in green)
Specialized Plant Cells:storage cells (amyloplasts)
Specialized Plant Cells:photosynthetic cells (contain many chloroplasts)
Specialized Plant Cells:root hair cells (epidermal)
Specialized Plant Cells:guard cells (stomata)
Specialized Animal Cells:blood cells (red erythrocytes & white leukocytes)
Specialized Animal Cells:skin cells
Specialized Animal Cells:bone cells (osteoclasts and osteoblasts)
Specialized Animal Cells:muscle cells
Specialized Animal Cells:muscle cells
Cross-section: bundles of muscle fibres
Longitudinal section: striations
http://cellbio.utmb.edu/microanatomy/muscle/striated_skeletal_muscle.htm
Specialized Animal Cells:gametes (sperm & egg)
http://www.bbc.co.uk/schools/gcsebitesize/img/bieggsperm2.jpg
Specialized Animal Cells:gametes (sperm & egg)
Specialized Animal Cells:fat cells (adipocytes)
Specialized Animal Cells:fat cells (adipocytes)
Large, central droplet of fat pushes the nucleus to one side.
http://www.mhhe.com/biosci/ap/histology_mh/adipos2.jpg
Specialized Animal Cells:nerve cell (neurons)
Specialized Animal Cells:nerve cell (neurons)
http://www.loria.fr/~rougier/artwork/neuro/img/neuron-SEM-2.png
Specialized Animal Cells:rod & cone cells (retina)
Specialized Animal Cells:lung cells
Specialized Animal Cells:figure 2 & 3 on p.59-60 of Nelson Perspective 10
Tissue Types
A collection of similar cells that perform a specialized function
4 major types:
http://www.bio.davidson.edu/people/kabernd/BerndCV/Lab/EpithelialInfoWeb/index_clip_image001.jpg
Muscle Tissue
Bundles of long cellsCapable of shortening or contractingFunction: movement
http://www.umm.edu/graphics/images/en/19917.jpg
Muscle Tissue
Classified based on 3 cell types
Type Example Control Fatigue Resistance
Cardiac
Heart Involuntary
Very
Skeletal
Limbs Voluntary
Not
Smooth
Organs that contract (e.g. stomach, intestine, bladder, uterus)
Involuntary
Yes
Tissue Types
A collection of similar cells that perform a specialized function
4 major types:
http://www.bio.davidson.edu/people/kabernd/BerndCV/Lab/EpithelialInfoWeb/index_clip_image001.jpg
Neurons that interact with each other
Conduct electrical impulsesCommunicates within the bodyExample: brain
Nervous Tissue
http://2.bp.blogspot.com/_guSOnFRs_Ks/TNvFt3IAtSI/AAAAAAAAAQc/_0oQdq46EmY/s1600/neurons.jpg
Tissue Types
A collection of similar cells that perform a specialized function
4 major types:
http://www.bio.davidson.edu/people/kabernd/BerndCV/Lab/EpithelialInfoWeb/index_clip_image001.jpg
Tissue Types
http://leavingbio.net/CELL%20DIVERSITY_files/image003.jpg
Connective Tissue
Function: structural support, insulation
Example: bone, cartilage, fat, bloodCells are held together by a liquid /
solid / gel matrix
Types of Connective Tissue
http://mycozynook.com/20_05ConnectiveTissue-L.jpg
Tissue Types
A collection of similar cells that perform a specialized function
4 major types:
http://www.bio.davidson.edu/people/kabernd/BerndCV/Lab/EpithelialInfoWeb/index_clip_image001.jpg
Epithelial Tissue
Thin sheets of tightly packed cells lining organs
Example: skin, lining of capillaries and digestive tract
Function: Prevent dehydration Reduce friction
Classes of Epithelial Tissue
http://cnx.org/content/m46048/latest/403_Epithelial_Tissue.jpg
Types of Epithelial Tissue
http://vet112and113.wikispaces.com/file/view/ooh!%20help.jpg/401994998/ooh!%20help.jpg
http://www.millerplace.k12.ny.us/webpages/lmiller/photos/636532/Epithelial%20Tissue%20Types%20%26%20Locations.bmp