From the blood cells that carry the oxygen in our blood to the branching neurons that control our thoughts, our bodies are made up of a dazzling variety of cells.
Scientists from institutions in Germany, Canada, Spain and the US have published a comprehensive study of how many individual cells of each type are in typical bodies.
Based on an exhaustive analysis of over 1,500 published sources, most adult males contain a total of approximately 36 trillion cellswhile adult females tend to have approximately 28 trillion cells. For comparison, a 10-year-old child would have in the region of 17 trillion.
In addition to the total number of cells, the study revealed something really interesting: if you group cells into categories based on their size, each size category contributes roughly the same amount to body weight.
“These patterns indicate an organism-wide trade-off between cell size and number and suggest the existence of cell size homeostasis across cell types,” researchers write in their published article.
In other words, there appears to be a natural balancing process where fewer larger cells and more smaller cells are produced to balance the categories. What’s more, the size differences in each category were also roughly similar.
Since the relative size of the body’s smallest cells (such as red blood cells) and the largest cells (such as muscle fibers) is like comparing the size of a shrew and a blue whale, this is a fascinating finding.
As the scientists point out, our cells are perfectly sized for their various roles—and any disruption to that range often suggests presence of disease. It is clearly important that this kind of cellular regulation occurs, and very cleverly.
Scientists have tried estimate the number of cells in our bodies before, and the new figure comes close to previous ones, but what makes this latest study special is the way it also tries to dig into comparable cell sizes.
Future studies will have the opportunity to look at exactly how our bodies regulate the size and number of cells that make us who we are—and how this regulation works to keep our bodies healthy and growing normally.
The researchers hope that their findings will be useful in many different studies of biology – and with that goal in mind, all the data from the analysis is now available. available online.
“Our data serve to establish a holistic quantitative framework for the cells of the human body and highlight large-scale patterns in cell biology,” said the teams writes.
The research was published in PNAS.
