Ch 8.4 Stem Cell Basics - Ted Talk 4 mins Stem Cells Ch 8.4 Stem Cell Basics - Ted Talk 4 mins

Ch 8.4 Objectives State the developmental stages from zygote to fetus. Explain how gastrulation forms the three germ layers with examples of each. State the two main types of stem cells and their characteristics. Explain the potency of particular stem cells and how this defines the types of tissues that they can form. Relate the source of the stem cells to the therapies the are applied to and link this to the range of controls and concerns regarding their use.

Embryo development Video of fetal development Fertilization – by gametes [sperm and ovum] to form one cell diploid cell. Zygote – fertilized egg [one cell] Morula – cell division to 16 [cleavage but no size growth] Blastocyst – inner [organism] and outer [placenta] layers present and implants into the uterus around day 6-7 Granula – 3 germ layers present [ecto, meso and ecoderms Embryo – up to the 8th wk [all major organs present] Fetus – 8 wk +

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Embryo - Layers of the Gastrula Do not copy Embryo - Layers of the Gastrula

Germ layers and cell differentiation Do not copy Germ layers and cell differentiation

Germ layers and cell differentiation This is highly simplified Ectoderm [outside] Skin Nerves Endoderm [inside] Pancreatic Respiratory Digestive Mesoderm [middle] Muscle Bone Blood cells

Germ layers and cell differentiation Do not copy Germ layers and cell differentiation

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Stem Cells Stem cells are an undifferentiated cell of a multicellular organism that is capable of giving rise indefinitely to more cells, and to all kinds of cells by differentiation. Cell differentiation is normally permanent/non-reversible. Embryonic stem cells – [ESC’s] obtained from 3-5 day old embryos Adult stem cells – [ASC’s] found in very small numbers in some adult tissues for tissue repair and replacement. Induced pluripotent – [IPSC’s] differentiated adult cells that have been synthetically re-programmed to act as stem cells.

Stem Cells Potency – the potential of a stem cell to differentiate into cell types Totipotent - fully potent [zygote up to morula 16 cells] – eg twins Pluripotent - [ESC’s] stem cells that can differentiate into any of the 3 germ layers + gametes or [PGC’s – primordial germ cells] Multipotent - arise from within one specific germ layer [ecto, meso or endoderm] Unipotent - replacement of one specific cell type [eg skin]

Multipotency – within a germ layer

Stem Cell Therapies Axolotls – organ and tissue regeneration – intro then skip in about 1:50 mins

Current Therapies 1/2 Bone marrow and blood stem cells – bone marrow contains haematopoietic stem cells [create all blood related cells] – used to treat patients that have undergone chemotherapy or to treat leukaemia [cancer of the white blood cells]. Cord Blood - stem cells can be taken from blood in an umbilical cord enhance blood and immune systems. Also used for treating diabetes Mesenchymal stromal cells also in cord blood, can be grown into bone, cartilage Intestinal stem cells – epithelial cells lining the gut have a remarkable ability to renew and repair

Current Therapies 2/2 Epidermal stem cells – the skin helps regulate body temperature and exclude infections, so treatments for skin problems such as burns and genetic disorders are of high importance using these cells. Embryonic stem cells – harvested from 3-5 day old surplus embryos from IVF clinics. They can be used to treat all types of tissue damage, but there use is not effective yet. Induced pluripotent stem cells – harvested from the patient, are pluripotent, but much research is required to understand their full potential and problem.

Ethical considerations Pros and Cons of stem cell research

If you, or a loved one required Human Stem Cell Therapy [HSCT], which of the current therapies would you consent to and why?

Resources Stem Cells wiki University of Utah Embryo development - Khan Academy - 12 mins University of Utah Overview Stem cells - Uni of Utah - interactive site  The nature of stem cells - video Utah 3:30 mins Unlocking stem cell potential - video Utah 4 mins Videos SciShow - Stem cells 4 mins Stem Cell Basics - Ted Talk 4 mins BBC Stem Cells - mini doco 4 mins How cells specialise -  the amoeba sisters 7:50 mins

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