Human Development and Stem Cells

Human embryonic development depends on stem cells. During the course of development, cells divide, migrate, and specialize. Early in development, a group of cells called the inner cell mass (ICM) forms. These cells are able to produce all the tissues of the body. Later in development, during gastrulation, the three germ layers form, and most cells become more restricted in the types of cells that they can produce.

2 minutes 18 seconds
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Mapping Cell Fates

As a human embryo develops, its cells become progressively restricted in the types of specialized cells that they can produce. Inner cell mass (ICM) cells of the blastocyst can make any type of body cell. Gastrula-stage cells can give rise to the cells of a given germ layer. Later, cells become even more restricted. For example, the pancreatic bud of the endoderm layer can only make the cells of the pancreas.

1 minute 28 seconds
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Creating Embryonic Stem Cell Lines

The inner cell mass (ICM) cells of blastocyst-stage early human embryos can be removed and cultured. These cells can be grown in the lab indefinitely. Various growth factors cause these cells to develop into a variety of differentiated cells, such as muscle or nerve cells.

1 minute 37 seconds
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Cytoplasmic Factors

Cytoplasmic factors play a significant part in determining how a cell develops. This segment discusses their importance in turning the appropriate genes on and off for proper development.

56 seconds
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Somatic Cell Nuclear Transfer Animation

Somatic cell nuclear transfer (SCNT) is a technique for cloning. The nucleus is removed from a healthy egg. This egg becomes the host for a nucleus that is transplanted from another cell, such as a skin cell. The resulting embryo can be used to generate embryonic stem cells with a genetic match to the nucleus donor (therapeutic cloning), or can be implanted into a surrogate mother to create a cloned individual, such as Dolly the sheep (reproductive cloning).

51 seconds
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Zebrafish Heart Regeneration

The zebrafish heart is similar to the human heart in many respects. But unlike the human heart, the fish heart closes wounds rapidly and then regenerates to nearly full function. Fibroblast growth factor (FGF) is an important molecule in the regeneration process.

2 minutes 29 seconds
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Newt Limb Regeneration

Urodele amphibians—newts and salamanders—are able to regenerate fully functional limbs in response to amputation. Cells in and near the limb stump dedifferentiate to form a mass of stemlike cells that can produce all the specialized tissues of the limb, such as muscle, nerves, and blood vessels.

1 minute 20 seconds
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