Embryonic stem cells | Cells | MCAT | Khan Academy

Summary

This script explores the journey of a fertilized egg, or zygote, through the stages of early embryonic development. It explains how the zygote becomes a diploid cell with full DNA complement, undergoes mitosis to form a morula, and then differentiates into the trophoblast and embryoblast, leading to the formation of a blastocyst. The focus then shifts to embryonic stem cells within the inner cell mass, highlighting their potential to develop into any cell type and the ethical debates surrounding their use, especially in contrast with the destruction of embryos in in-vitro fertilization processes.

Takeaways

• 🌟 The script discusses the process of fertilization where a sperm cell meets an egg cell, leading to the formation of a zygote.
• 🧬 After fertilization, the zygote, which is haploid, becomes diploid, containing the full set of DNA (2N) necessary for a human cell.
• 💧 The zygote undergoes mitosis without significant growth in size, leading to the formation of a multicellular structure known as the morula.
• 🌱 The morula differentiates into an outer layer called the trophoblast and an inner cell mass known as the embryoblast, which will develop into the organism.
• 🌀 The embryoblast is also referred to as the inner cell mass and is composed of embryonic stem cells, which have the potential to become any cell type in the body.
• 👶 The trophoblast will eventually develop into the placenta, serving as the interface for nutrient and waste exchange between the fetus and the mother.
• 🔬 The debate around embryonic stem cells centers on their potential to cure diseases and the ethical concerns of destroying embryos for research purposes.
• 🤔 The script highlights the difference between embryonic stem cells and somatic (adult) stem cells, with the former being more 'plastic' or versatile in their potential cell types.
• 🧪 The term 'blastomere' is introduced for the individual cells resulting from the early mitotic divisions of the zygote.
• 🌐 The script points out the ethical inconsistency in the public debate, noting that in-vitro fertilization also results in the destruction of embryos, similar to stem cell research.
• 🔍 The potential of embryonic stem cells to repair damaged tissues or grow new organs is a significant area of scientific research with both promise and controversy.

Q & A

What is the initial result of the fertilization of a sperm and an egg?

The initial result of the fertilization of a sperm and an egg is the formation of a zygote, which is a diploid cell with a full complement of DNA (2N).

What happens to the zygote immediately after fertilization?

Immediately after fertilization, the zygote undergoes cleavage through mitosis, which results in a series of cell divisions without a significant increase in size, leading to the formation of a morula.

What is the term used to describe the early stage of cell division in the developing embryo?

The term used to describe the early stage of cell division in the developing embryo is 'morula,' which is named for its resemblance to a mulberry.

What differentiates the cells of the morula into two distinct types?

The cells of the morula differentiate into two distinct types: the trophoblast, which are the outer cells, and the embryoblast, which are the inner cells.

What is the term for the fluid-filled space that forms between the trophoblast and the embryoblast?

The fluid-filled space that forms between the trophoblast and the embryoblast is called the blastocoel.

What is the term used to describe the stage of development after the morula, where cells have differentiated into trophoblast and embryoblast?

The term used to describe this stage of development is 'blastocyst.'

What is the potential role of embryonic stem cells in medical treatments?

Embryonic stem cells have the potential to differentiate into any cell type in the body, which could be used for repairing damaged tissues, treating diseases, and potentially growing new organs for transplants.

What ethical debate is associated with the use of embryonic stem cells?

The ethical debate revolves around the destruction of the embryo to extract embryonic stem cells, as the embryo has the potential to develop into a human being.

What is the difference between embryonic stem cells and somatic (adult) stem cells?

Embryonic stem cells have the potential to differentiate into any cell type in the body, whereas somatic (adult) stem cells are more limited in their potential and can only form certain types of cells.

How does the process of in-vitro fertilization relate to the ethical debate on embryonic stem cells?

In-vitro fertilization also results in the creation of multiple embryos, many of which are not used and can be destroyed, highlighting a similar ethical issue regarding the destruction of embryos.

What is the term used for the individual cells resulting from the early divisions of a zygote?

The individual cells resulting from the early divisions of a zygote are called blastomeres.