Questions and Answers
What is the embryonic period?
The embryonic period is the first 8 weeks after fertilization.
What is cleavag?
A sequence of rapid mitotic divisions without cell growth.
What are the three germ layers formed during gastrulation?
Ectoderm, mesoderm, and endoderm.
What hormone does the syncytiotrophoblast produce?
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Which of the following statements about stem cells is True?
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What is the defining feature of totipotent stem cells?
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Hematopoietic stem cells (HSCs) are classified as __________ stem cells.
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What applications can stem cells potentially be used for?
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Adult stem cells have a pluripotent differentiation capacity.
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What is a challenge of embryonic stem cell research?
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Study Notes
Embryogenesis
- Embryology studies the development of embryos from fertilization.
- The embryonic period lasts the first 8 weeks after fertilization, forming three primary germ layers.
- The fetal period is 30 weeks, during which organ growth and development continue.
- The human body contains around 220 cell types, totaling approximately 50-75 trillion cells.
Stages of Embryonic Development
- Fertilization: Fusion of sperm and ovum creates a zygote.
- Cleavage: Rapid mitotic divisions produce a multicellular structure without growth, starting approximately 30 hours post-fertilization.
- Gastrulation: Blastula transforms into a gastrula featuring ectoderm, mesoderm, and endoderm layers.
- Organogenesis: Development of organs begins after the establishment of germ layers.
Key Structures in Embryogenesis
- Trophoblast: Outer layer of cells forming the placenta.
- Blastocoel: The inner cavity of the blastocyst, developing into body cavity.
- Inner Cell Mass (Embryoblast): Gives rise to the embryo.
Role of hCG
- Syncytiotrophoblast produces human chorionic gonadotropin (hCG), crucial for pregnancy maintenance and detectable in blood tests after two weeks.
Stem Cells
- Stem cells are unspecialized cells with self-renewal and differentiation capabilities.
- They act as mother cells, continuously reproducing and forming specialized cell types.
Properties of Stem Cells
- Unspecialized: Lack specific structures for specialized functions.
- Self-Renewal: Can divide indefinitely.
- Differentiation (Potency): Can become specialized cells.
- Plasticity: May generate cell types from different tissues.
Types of Stem Cells
- Totipotent: Can develop into any cell type, including placenta; able to form a complete organism.
- Pluripotent: Can become any cell type in the body; inner cell mass of blastocyst develops into ~200 cell types.
- Multipotent: Restricted to specific tissues; can become various cell types within a tissue/organ.
Types of Pluripotent Stem Cells
- Embryonic Stem Cells (ESCs): Derived from inner cell mass of blastocyst, with significant self-renewal and differentiation potential.
- Induced Pluripotent Stem Cells (iPSCs): Adult cells genetically reprogrammed to behave like ESCs, capable of differentiating into specialized cells for therapies.
Types of Multipotent Stem Cells
- Cord Blood Stem Cells: Harvested from the umbilical cord; used for treating blood disorders.
- Placenta Stem Cells: Have potential for healing, but may contain maternal cells.
- Tissue-Specific Stem Cells: Found in developed organs, include Haematopoietic Stem Cells (HSCs) and Mesenchymal Stem Cells (MSCs).
Haematopoietic Stem Cells (HSCs)
- HSCs are multipotent and can self-renew while differentiating into various blood cells.
- Located in specialized microenvironments known as HSC niches.
MSCs Functionality
- MSCs contribute to creating specialized skeletal tissues.
Applications of Stem Cells
- Can treat diseases and regenerate damaged organs, akin to organ transplants.
- Stem Cell Transplantation (SCT): Utilizes donor stem cells to restore normal blood cell production in diseases like leukemia.
Experimental Uses
- Cell therapy applied to graft new skin cells for burn victims and regenerate corneas.
- Potential to create insulin-secreting pancreatic cells for Type I diabetes treatment.
Challenges of Stem Cell Research
- Ethical Concerns: Issues surrounding the morality of using embryonic stem cells due to blastocyst destruction.
- Embryo Viability: Debate on when life begins affects perspectives on stem cell research.
- Tumor Risk: ESCs may become tumorigenic due to mutations in culture.
- Acceptance of umbilical cord and adult stem cells widely considered morally acceptable.
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Description
This quiz covers Chapter 1 of the Medical Laboratory Sciences on Haematopoietic Stem Cells. Topics include embryogenesis, the definition and properties of stem cells, the various types of stem cells, their applications, and the challenges faced in stem cell research.
