Stem cells are immature cells that have the ability to renew and differentiate to form different types of cells; in other words, they are cells that have the ability to develop into various kinds of other types of cells. For example, blood cells, nerve cells, immune cells etc. Human stem cells can be found in adult bone marrow or human embryos.


The difference between the stem cells that can be found in adult bone marrow and human embryos is that the cells found in human embryos can develop into any type or cell, whereas the stem cells found in adult bone marrow can develop into many types of cells but not all.
Stem cells can be very useful in treating a number of medical issues. Some of these include treating Parkinson’s disease by developing new brain cells, making replacement heart valves, rebuilding bones and cartilage, and repairing damaged immune systems.
Take a look at the following diagram that illustrates the potential application of human stem cells; in other words, the differentiation that stem cells undergo:

There are a number of advantages and disadvantages to using stem cells in medicine. The table below has been provided to help highlight these:
Advantages | Disadvantages |
Medical benefits – stem cell research offers benefits in regenerative medicine and also with therapeutic cloning in order to treat some chronic illnesses. | Unknown side effects – because research into stem cells is fairly new, the side effects of their use remains unknown. Further advancements into research also need to be made before stem cell treatment can be used safely. |
By researching stem cells, we have gained a better knowledge into human growth and how the human body works, which is vital in the advancement of medicine. | Moral argument – the main moral argument to stem cell research is that altering the structure of genes is interfering with the natural functions of the human body, possibly creating greater risks in the development of new diseases. |
This research can also have a huge benefit on correcting birth defects in unborn children due to the effects of stem cells on embryos. | Whilst researching stem cells, we are also researching human cloning. Many people view this as having a negative and possibly detrimental effect on our society (we will discuss more about the process and the advantages and disadvantages of cloning towards the end of this course). |
Another example below illustrates the differentiation process but is specific to immune cells:

This diagram is purely to illustrate the differentiation in the development of specialised cells. You are not required to know how stem cells develop for the examination; however, we will go into further detail about some of these individual cells when we discuss the immune system later in this topic.