Okay, think of the last time you gave blood.

Or maybe you've had surgery, like you've had your tonsils or appendix removed.

You know some of what happened to those things - the blood was tested, the tissue was biopsied, perhaps you had treatment.

But what happened next?

What did the hospital, doctors, or scientists do with your cells?

If you think that material was destroyed, you might be right, but you might be wrong.

In the United States, the 1990 court case "Moore v the University of California" decided that as long as your tissue is anonymized, meaning your name and identification isn't longer associated with it, it can be used in research and science.

You don't have to be informed, or asked for consent.

Once your cells are removed from your body, you no longer own them, or have any say in what happens to them.

Most of the time, this is no big deal, you weren't using those cells anyway.

But in some situations, this ethical issue becomes a lot more complicated.

Here's one example: In Sweden, 1962, a married mother of several children made the decision to end her pregnancy.

After performing the abortion, without informing the woman or getting her consent, the doctor sent the fetal tissue to researchers.

It changed hands several times, and underwent a number of procedures, until the fetal lung tissue was turned into a cell line, which is a group of reproducing cells from a single genetic source.

Cell lines allow researchers to test the effects of different chemicals or treatments on cells while controlling for genetic variation.

This cell line has been used in labs to successfully develop vaccines, including a rabies vaccine, and the rubella vaccine, ever since.

Once the researchers realized how useful the cell line could be, they contacted the biological parents to obtain their medical history, to ensure the cells were healthy.

When the woman learned what had happened to the fetus, she was understandably upset that the cells has been used and experimented upon without her consent..

Even in 2013, 51 years after the fetal cells were first obtained, she's quoted saying: "They [the researchers] were doing this without my permission!

This could not happen today!"

Ethically, many people argue that saving hundreds of millions of lives is more important than what one woman wants for cells she's chosen to remove.

But what about the millions and millions of dollars in revenue generated by those vaccines?

Without the cells, there'd be no vaccine, but there'd also be no profit.

So does the donor deserve a piece of the pie?

In this case, the woman just wanted to put the ordeal behind her, but in other cases, patients and their families argue that by using and selling their cells for profit, without their consent, researchers are stealing from them.

Henrietta Lacks, for example, died of cervical cancer in 1951, leaving behind 5 children, and a tissue sample that may or may not have been removed without her consent.

And this tissue was fascinating.

When scientists fed the cells, they continued to reproduce outside of Henrietta's body - something scientists had never done before.

They became the HeLa cell line, and today, HeLa products can sell for as much as $10,000 a vial.

But, because the tissue used to create HeLa cells was removed from Henrietta's body in the course of her medical treatment, legally they no longer belong to her or her family.

So her relatives can't claim any of those profits.

Few would argue that using these cells to develop new treatments or medicines and save millions of lives is a bad thing.

But the ethical concerns are valid: have researchers taken advantage of poor, sick, or vulnerable people for profit?

Legally, this is allowed, but is it really ok?

Would you want your cells used for science without your consent?

And if they made a pharmaceutical company millions of dollars, would you feel entitled to some of that money?

As always, let us know your thoughts in the comments section below.