Stem cells
Stem cells in humans
A cell found in foetuses, embryos and some adult tissues that can give rise to a wide range of other cells. are cells that have not undergone When an unspecialised cell becomes a more specialised cell type.. A cell which has not yet become A cell that has become differentiated to carry out a particular function, eg red blood cell. is called undifferentiated.
An An organism in the early stages of development. develops from a fertilised egg. All of the cells in an embryo start off identical and undifferentiated. These cells are called A type of stem cell found in the embryo, capable of dividing into almost any cell type. and can become specialised to form any type of cell. They do this by switching genes on and off. For example, if one of the embryonic stem cells formed a muscle cell, it would switch on the genes to turn it into a muscle cell and switch off the genes that would cause it to become a different type of cell.
The embryonic stem cells receive signals from other cells so that they turn the correct genes on and off. A whole new organism with skin, eyes, heart, liver and all of the organs it needs, will develop from the embryonic stem cells. This allows the organism to have all the tissues it needs with the correct functions to be able to survive.
Some stem cells remain in the bodies of adults. A type of stem cell found in specific locations in adults. Adult stem cells can only differentiate into a limited number of related cell types. are found in limited numbers at certain locations in the body, including the:
- brain
- eyes
- blood
- heart
- liver
- bone marrow
- skin
- muscle
Adult stem cells are unspecialised but can become specialised much later than embryonic stem cells. They can differentiate into related cell types only. For instance, adult stem cells in the Soft tissue found inside bones that produces new blood cells. can differentiate into blood cells and cells of the The body's defence system against entry of any foreign body, including pathogens and agents such as pollen grains. The role of the immune system is to prevent disease., but not other cell types.
Stem cells in plants
Cell division in plants occurs in regions called A region in plant shoots and roots in which cells are dividing, and so are undergoing mitosis..
Cells of the meristem divide by A type of cell division which produces daughter cells identical to the parent. and produce unspecialised cells. These cells can differentiate to produce all types of plant cells at any time during the life of the plant.
The main meristems are close to the tip of the shoot, and the tip of the root.
In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated - they enlarge and develop A space within the cytoplasm of plant cells that contains cell sap..
Learn more about stem cells with Dr Alex Lathbridge.
Listen to the full series on 91热爆 Sounds.
Dr Alex Lathbridge breaks down the key facts about stem cells. Listen to the full series on 91热爆 Sounds.