There are many cells in the human body: 37.000,000 million (37,000,000,000,000)

You know that our body is made of cells - but just how many? Turns out that question isn’t all that easy to answer

How many cells make up our body? It’s actually not all that easy to answer that simple question. But recently, scientists have made a pretty good effort. And their final count is 37.2 trillion.

Calculating the number of cells in the human body is tricky. Part of the problem is that using different metrics gets you very different outcomes. Guessing based on volume gets you an estimate of 15 trillion cells; estimate by weight and you end up with 70 trillion.

Another figure that is illustrative of these “astronomical” figures is the number of neurons in the brain. There ar 86,000 million neurons and each of them fire from 5 to 50 times a second. That is 430 billion to 4.3 trillion signals sent every second, or 204,336 trillion signals per day.

Carl Zimmer at Nacional Geographic Explains:

So if you pick volume or weight, you get drastically different numbers. Making matters worse, our bodies are not packed with cells in a uniform way, like a jar full of jellybeans. Cells come in different sizes, and they grow in different densities. Look at a beaker of blood, for example, and you’ll find that the red blood cells are packed tight. If you used their density to estimate the cells in a human body, you’d come to a staggering 724 trillion cells. Skin cells, on the other hand, are so sparse that they’d give you a paltry estimate of 35 billion cells.

How did these researchers come up with 37.2 trillion? They actually broke down the number of cells by organs and cell types, going through the literature available to come up with a detailed list of volumes and densities in everything from intestines to knees. So, for example, there are 50 billion fat cells in the average body, and 2 billion heart muscle cells. Adding all those up, they got 37.2 million. (This doesn’t include any of the millions of microbes living on you, by the way.)

The authors point out that this isn’t simply a good pub trivia question. Using cell counts, and comparing them to the average, can help doctors identify problems. “Knowing the total cell number of the human body as well as of individual organs is important from a cultural, biological, medical and comparative modelling point of view,” they write.

Adapted from an article by Rose Eveleth

SMITHSONIANMAG.COM
2013

https://www.smithsonianmag.com/smart-news/there-are-372-trillion-cells-in-your-body-4941473/