Differentiation

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EmbryogenesisPotency

Stem CellsSpecialized Cells

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

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

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

Embryogenesis: Gastrulation

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

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

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)

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)

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

Skeletal

Limbs Voluntary

Smooth

Organs that contract (e.g. stomach, intestine, bladder, uterus)

Involuntary

Tissue Types

4 major types:

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

4 major types:

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

4 major types:

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

Differentiation

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