For years, the number 37 trillion cells was widely accepted in popular science. This estimate originated from a 2013 study where scientists initially counted cell types in the human body.
A large-scale study in the journal PNAS challenged this, analyzing over 1,500 scientific publications to determine the cell mass for people of various sexes, ages, and weights:
- Adult man (70 kg): approximately 36 trillion cells
- Adult woman (60 kg): approximately 28 trillion cells
- 10-year-old child (32 kg): approximately 17 trillion cells
Most numerous cells:
The human body contains over 200 major cell types, differing in size, shape, and function.
- Red blood cells: Transport oxygen and carbon dioxide, forming the majority of cells in the body.
- Neurons: Transmit signals, vital for the nervous system.
- Muscle cells: Contract through specialized proteins.
- Beta cells: Produce insulin in the pancreas.
- Platelets: Aid in blood clotting, though they are fragments of bone marrow cells (megakaryocytes).
Blood cells dominate reproduction, composing nearly 90% of daily cell renewal.
Myth: “A new body every 7 years”
The body is dynamic, replacing nearly 330 billion cells daily. The replacement rate varies by tissue:
- Intestinal epithelium renews every 5 days due to digestive enzyme exposure.
- Blood cells replace quickly.
- Brain and heart regenerate slowly; many neurons last a lifetime, and the heart muscle’s regeneration is limited.
Thus, the idea that every atom and cell is replaced every seven years is a myth.
Factors influencing cell count:
Cell numbers vary individually, affected by height, weight, age, and muscle, fat, and organ ratios. A taller, heavier person has more cells than a shorter, lighter one. However, cell size varies significantly.
Bacteria: 10 times more or 1 to 1?
Previously, it was thought our microbiome had 10 times more bacteria than human cells. Recent calculations debunked this. In 2016, scientists found a typical 70-kilogram person has about 38 trillion bacteria and 30–36 trillion human cells, indicating a 1:1 ratio.
Source: Rambler
Photo is illustrative: pexels-marek-piwnicki-3907296-11516492
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