Cell Life Times
Adult humans have about 37 trillion cells (37,000,000,000,000). Each has its own life span ranging from a few hours to our entire lifetimes. Red blood cells live for about four months. White blood cells average more than a year. Skin cells die in about 18 days. Colon cells live less than five days. Some brain cells live an entire lifetime.
The number, arrangement, life, and state of our cells undergo constant change. They are never the same from moment to moment. For the middle aged like me, most of my body is less than ten years old, although in total cell's average about a 16 year lifespan.
Our brains are standout exception to this aging. Most brain cells live as long as we do. A few die, a few arrive to fill in, but most are with us through our entire lives. This persistence in our brains existence is part of the reason we perceive ourselves as being more consistent than we are.
We are more than just human cells, our genetic makeup is only a tiny fraction of the total genes that exist inside our bodies. There are many bacteria that live inside us, on us, with us.
In this sense we humans are more like biomes or ecologies than individuals. In a 200-pound adult, 5 pounds of us are not truly us. For every human gene in our body, there are 360 microbial genes. This includes viruses, micro-phages, and other tiny organisms.
There are about a two thousand trillion bacteria (2,000,000,000,000,000) in our bodies. Our human cells are outnumbered by twenty to one by bacteria. Human cells tend to have more weight and size, but lose the numbers and diversity game.
Bacteria and yeast colonies live through most of the body. Coexisting in symbiotic relationships with us from our bellybuttons to our eyebrows, from our blood vessels to our ear canals. Bacteria are so vital to our survival that we would soon die without them.
More than 500 species of our co-life-forms are living at any one time in an adult intestine.
Our friendly passengers produce molecules that help us harness energy and extract building blocks from food, act as a first line of immune defense, and provide communication pathways between our cells.
Even though an individual cell may exist for a period of time, The contents of cells are also constantly changing. All cells are in constant motion within.
Inside each cell has a ongoing flurry of activity as it builds, transports, uses, then recycles proteins. There are about 100,000 different kinds of proteins necessary for each human cell to function. Each protein exists for about one to two days.
Molecules go in and out of cells constantly. Large complex molecules containing energy, raw materials, signals for behavior and more; pass in, move through, and leave cells regularly. Smaller molecules like oxygen, water, and carbon dioxide move in, out, and about cells freely.
|Very well, then I contradict myself, |
I am large, I contain multitudes.
We have a over five hundred (500) times the number of cells in our bodies as there are stars in the milky way galaxy.
It is our shared illusion to perceive ourselves as humans rather than ecosystems with a human framework. Not sensing the cells, the proteins, or bacteria allows us to ignore their fundamental part of our existence.
We think ourselves a single thing, but we are much more than that.
At each moment we are something. In the next moment we have changed all over. As time passes what we are is completely different.