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stem cells – ethical issues. National 4 & 5 Biology – multicellular organisms. Learning outcomes. By the end of this lesson you will be able to: - describe the different types of stem cells - explain how these stem cells can be obtained
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stem cells – ethical issues National 4 & 5 Biology – multicellular organisms
Learning outcomes • By the end of this lesson you will be able to: • - describe the different types of stem cells • - explain how these stem cells can be obtained • - the ethical issues related to using these stem cells
Embryonic Stem Cells (ESC’s) Can turn into any type of cell – they are ‘pluripotent’ Only occur in early development – 5 to 7 day old embryos Their use in research is strongly criticized by people who believe it is unethical to kill embryos for their cells. Stem cells from foetuses are almost as powerful, and can be used from the blood of umbilical cords.
Source of embryonic stem cells Cloned Embryos • Deliberately create embryo • Remove cells from 5 day old blastocyst & discard embryo Aborted Foetus • 5 – 10 week old foetus • Stem cells isolated from tissues which develop later on into ovaries or testes • Not pleuripotent stem cells – have already started to specialise (have limited use) ‘Spare’ Embryos from IVF • Embryos created in vitro can be used as a source of stem cells • Several embryos created at the one time & stored
What are adult stem cells? Adults also contain stem cells, found in many organs, including bone marrow, brain, skin and muscle. Adult stem cells normally maintain and repair damaged tissue, and can usually only make a small number of cell types. For example, adult stem cells in the skin only normally form skin cells. Research shows that some adult stem cells can be manipulated to produce many different cell types (e.g. brain stem cells can make muscle cells). This is called plasticity.
What are bone marrow transplants? Stem cells in bone marrow have been used to treat diseases that affect blood cells, such as leukaemia • Bone marrow is harvested from a suitable donor under general anaesthetic. • The patient’s abnormal blood cells are destroyed by chemotherapy and/or radiotherapy. • The donated bone marrow is injected into the patient. • Stem cells in the injected bone marrow end up in the patient’s bone marrow, where they start to divide and produce new blood cells.
Advantages of using adult stem cells Adult stem cells are not as powerful as embryonic stem cells, but they do have other advantages. • They come from volunteers so they are more ethically acceptable. • A patient’s own stem cells could be used to treat their own disease, avoiding the problem of immune rejection. • It might be easier to guide their development into specific cell types. Less risk of uncontrolled growth (can cause cancers). There is a great deal of research into using adult stem cells to treat diseases. They could reduce the need for organ transplants, which have long waiting lists.
Glossary (1/2) • bone marrow –The spongy tissue in the centre of bones that is a rich source of adult stem cells. • differentiation – The process by which a cell specializes into a specific type. • division – The process by which one cells splits into two new cells. • elongation–The process by which a cell increases in length. • embryo –The early stage of animal development, when it is just a cluster of cells. • foetus – The stage of animal development after 8 weeks of development.
Glossary (2/2) • gestation – The period of mammalian development in the uterus. • growth – An irreversible increase in mass of an organism. • regeneration – The replacement of lost tissue or organs by new ones grown from stem cells. • stem cell –An unspecialized cell that can potentially become any type of cell.
