Apoptosis is the programmed death of billions of cells in your body every day … even before birth. Without this death, there wouldn’t be life.
Cells don’t live forever in the human body; they have different life spans based on the type and function of the cell, from a few days to a year or more. Certain cells in the digestive tract live just days, while immune system cells can last for six weeks and pancreatic cells up to a year.
About 100 million cells die every minute in your body, so death is an integral part of life. This programmed cell death is called apoptosis—from the Greek for “falling off”—and it’s at work in the body even before we are born.
When we think of newly forming life in the womb, we think of the multiplication of cells. Although there are only a few dozen cells that form the placenta and embryo five days after conception, from there they grow exponentially to form the fetus.
At week nine the torso, head, arms, hands, legs, and feet are clearly visible, and a couple of weeks later, the fingers and toes are perfectly defined. We don’t stop to think that for them to form, the cells at the ridges between the fingers and toes die. Only specific cells in specific places expire, while those directly adjacent are transforming into various skin cells, each with its specific functions. How is all this governed?
Generation, growth, and death go hand in hand. In the nine-month gestation period a human fetus undergoes the death and replacement of millions of cells. Even brain cells that rarely die in adults until we reach a certain age or suffer an accident die in the womb! There is a pruning process among cells as the fetus gets ready for the outside world.
Going deeper, this cell death not only preserves the health of the fetus but also of you and me. Cells can become damaged in various ways (e.g., infection, accidents, inaccurate or interrupted replication) so that they are no longer capable of assuming their role in the body. Such cells have an internal self-destruct mechanism that takes them out of the normal cell circuit.
“Is it too harsh to call that suicide?” Galacti asks. “Or is it more like a machine that shuts down? I guess since you talked about proteins and cells as machines; let’s go with that analogy. In fact, we can think of cells as a car supply chain that has to take vehicles damaged by hail, storms, or rough handling into account. There has to be an organized pathway of atomization and waste removal to handle such mishaps.”
Good point. Macrophage cells are like recyclers as they engulf and ingest debris from a self-destructed cell or repair and regenerate it to rejoin the supply chain.
Even before birth, the processes of life, death, and regeneration are intertwined and taking place simultaneously.
Bones, skin, and the digestive system are always remodeling as apoptosis—the death of cells—works hand in hand with its counterpart, mitosis, to generate, renew, and resculpt the body.
Menstruation is apoptosis at its most intimate and delicate, creating and then destroying the inner lining of the uterus when a woman doesn’t become pregnant and then regenerating the lining of the uterus every month.
There’s finely tuned chronobiology with JIT growth, JIT death, and proper evacuation of the dead remains to cleanse the body and prepare for a new cycle. Programmed cell death is responsible for well-formed bodies as well as general health.
For example, 200 billion red blood cells are formed every day, and thus, to maintain the equilibrium in our bodies, 200 billion red blood cells are also planned to die every day.
Galacti points out that this is true for animals, birds, insects, and plants also. He cites the examples of a tadpole’s tail cells dying as it transforms into a frog or of the programmed death of a larva to promote its growth into a moth or butterfly.
In plants, ripe fruit can easily be picked, hazelnuts separate from their husk, and leaves fall from trees in autumn due to apoptosis—cells dying in specific locations at specific times to allow this severance. This timed death is an integral part of chronobiology that pervades the cyclical rhythms of life.
This post is an excerpt from chapter 7.11 of Inventory of the Universe.
The Explanation Blog Bonus
This first video is a bit technical, it’s short so it’s an easy watch especially because it emphasizes the multiple ‘pathways’ we’ve discussed. The multitude of processes within processes for an event (like apoptosis) to take place. These are a progressive sequence of highly complex, just in time procedures that must occur for the climactic event (apoptosis) to be accomplished.
This video is a graphic presentation of apoptosis. I don’t understand all the technical terms but it’s fascinating to watch the enormous activity involved–all coordinated–to cause a diseased cell to commit suicide.
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