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Phagocytosis is a process used by cells to engulf and subsequently ingest particles of nutrients or bacteria. This process is a very important part of cell function, allowing cells to grab vital nutrients and allowing the body to protect itself from harmful bacteria. A cell that specializes in this process is known as a phagocyte. It is one among a family of processes collectively referred to under the blanket term “endocytosis,” which refers to any sort of ingestion of material by a cell. The opposite is exocytosis, the expulsion of unwanted material from a cell.
In this process, a cell deforms its membrane to form a little cone around the piece of material that is to be absorbed, and then it closes the sides of the cone, hugging the particle in the cell membrane to create what is known as a phagosome or food vacuole, like a little envelope of material surrounded by the cell membrane. The phagosome, in turn, is passed into the cell for absorption by the lysosomes, the cell structures that specialize in digesting materials that enter the cell. The lysosomes break the phagosome down into its component materials, passing useful compounds on to other structures in the cell and expelling the rest as waste material. In the case of some infectious or harmful material, the phagosome may enter a peroxisome, a special cell structure that helps to rid the body of toxins.
In unicellular organisms, phagocytosis is a critical function, as, without it, the organism will not survive. Some of these organisms have adapted special traits that allow them to track food, orienting themselves in the direction of useful particles that they can ingest. In multicellular organisms, it tends to be a more passive process, but it is still crucial for the survival of the individual cells, ensuring that they get the nutrients they need to function.
Immune system cells also perform phagocytosis, trapping harmful materials when they enter the body and destroying them so that they cannot cause damage. In some cases, the body may respond with inflammation, as a flood of immune system cells rushes to a location to deal with unwanted invaders. When the immune system can no longer cope with harmful materials, or when these materials resist the ingestion process, the consequences for the host body can be quite unpleasant.
I've heard that the theory is we originally got mitochondria in our cells because of phagocytosis. Mitochondria are quite strange, because even though they seem to be a necessary part of most animal cells, they are also quite distinct and have their own kind of DNA (which is passed down differently from our own DNA. That's why it can be used in some kinds of research where normal DNA can't be).
They think it was originally a bacteria that got absorbed by phagocytosis and entered into a symbiotic relationship with the devouring cell.
I think that's so intriguing.
@umbra21 - In fact I think it does help kids to get better if they can visualize the illness in this way.
I've even heard of video games that are available to sick kids, particularly ones who are sick in hospital with something serious, where they can go on a journey through the human body "fighting" cancer cells or whatever else they have.
I don't know if it increases their responses to treatment, or if it simple helps them by decreasing their frustration with their situation.
The cool thing is, the game was developed by a boy who was in the hospital with a serious illness himself.
He was given a wish by the Make a Wish foundation and having the game made and allowing it to be available for free to sick kids was his wish. It's more about chemotherapy than about phagocytosis though, but still, cool huh?
I know it's not very scientific, but this is the process I encourage kids to think about when they aren't feeling well. Just imagine all your white blood cells, storming up your blood vessels, attacking and swallowing the harmful bacteria, I tell them.
Or I might encourage them to imagine cheering on the white blood cells or giving them strength.
It allows them to feel more like they are in control, particularly when they are quite sick with something frustrating, like chicken pox.
And it might have a placebo effect as well, who knows? If they think that imagining the white blood cells and encouraging them to work will actually make them better, perhaps it will help some.
At any rate, it gives them something to do.