Human Body Number of Cells: Massive New Analysis Reveals How Many Cells a Person Has

Cells serve as the building blocks of the body's tissues and organs. Scientists have now been able to estimate how many cells make up the human body.

How Many Cells Does the Human Body Have?

The new analysis covered over 1,500 studies. According to the findings, an average male human has roughly 36 trillion cells, while their adult female counterparts have 28 trillion cells. On the other hand, children who are 10 years old have roughly 17 trillion cells.

To come up with such figures, the study authors factored in the number and size of 400 different cell types in 60 different tissues, including immune, nerve, and muscle cells.

Though similar estimates have been made among human males in the past, this is the first study that examines the link between cell number and size in the whole body.

Ian Hatton, the study's lead author who is from the Max Planck Institute for Mathematics in the Sciences, expresses how surprising it was to witness an inverse correlation between cell count and size in the entire human body. This means that when a cell is larger, its count is smaller relative to their smaller counterparts. Going further, this also means that if the cells were to be clustered according to size, each cell group would account for the same amount to the body's overall mass.

Hatton explains that the pattern spans seven magnitude orders in the size of cells, from red blood cells to the biggest muscle cells, that can be likened to the mass ratio of a blue whale and a shrew.

Anatomical Models as a Limitation

The analysis, however, contains limitations that the researchers also acknowledge. For one, the researchers typically focused on the "average" bodies of adults and childrens. For their analysis, the benchmark male adult weighed 70 kilograms, while female counterparts weighed 60 kilograms, and average children weighed 32 kilograms.

These references were taken from the International Commission on Radiological Protection. Given this, weight and size variations among humans were not factored in.

Hatton adds that there is a huge variation across various anatomical models. However, aside from muscle and fat content variations in their respective cells, most variations may not be as significant relative to other error sources linked to setting boundaries in human body cell count.

Nevertheless, the researchers acknowledge the uncertainty in the numbers. They had to depend on inferences on cell dimensions that were made via microscopy or other indirect techniques. They also gauged cell count for children and adult females with studies that mainly covered adult males in their sample.

Professor Eric Galbraith from McGill University, who also serves as the group leader, explains that there is still a gap for reference females and males, especially. It is necessary to conduct further research to fill in such gaps.

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