1 What are cells?
If we look at a human body with close inspection, we get to know it is made up of a vast array of different and vital parts. Every part is nothing but an amalgamation of cells. A cell is a tiny building block of life. Mostly, these cells are so small that we can only see them with the help of a microscope. They are not visible to the naked eye.
2 The Size of a Cell
Depending on the type as well as function, cells differ in size. The human body, on average, has around 200 varying kinds of cells. Your average cell will hold a volume of merely four billionths of one cubic centimeter. It will weigh not more than just a nanogram.
3 Number of Cells in the Human Body
Given the tiny size, there must be plenty of cells present in the human body. It is impossible to get a precise count of the total number of cells in the human body. We cannot see them, and they are simply way too many to be counted. Having said that, scientists, with the help of advanced mathematics, have calculated what, as per them, could be a rough or average number of cells in a human body.
4 The Technique Used to Count
Some scientists attempted to estimate the cell number in our bodies based on the weight of an average cell and the weight of an average human body. This simple mathematical calculation gave them an approximate number of 70 trillion cells! Other scientists based their estimates on the volume of an average cell as well as the volume of an average human body. This arithmetic relied on volume, and the approximate we got was 15 trillion cells! There is a pretty high difference between these two estimates.
5 Counting Cells is Not So Easy
Things are way more complex here. Scientists have realized that cells vary in size and density as per their type in the human body. So clearly, counting them on the basis of weight and volume is not right. For getting the most accurate estimates possible, scientists tried studying the density and volume of every type of cell present in our bodies. As per their studies, an average human body comprises 2 billion heart muscle cells and 50 billion fat cells. Red blood cells are at a whopping 20 to 30 in numbers. So, to conclude their studies, the team added all these numbers together. The grand total came out to be 37.2 trillion cells. (See How many bones in the human body?)
6 There is No Fixed Number
We must not forget that 37.2 trillion cells are the sum of the number of cells in an average human body. 'Average' is the keyword here. Every human body will have fewer or more cells than that of the total estimate. It all depends on how your body size is bigger or smaller than the average human body.