Human bodies are made of cells
All living organisms are made up of cells. In fact, every part of your body is built of these microscopic structures, working in perfect harmony.
But, what is a cell? A cell is defined as the basic unit of life. Think of it as a 24/7 factory dedicated to having yourself alive. As every factory, all cells have some main components:
a) The nucleus, which is like the boss’s office. The boss, which in this case would be the genetic material, known as DNA, is contained and protected inside it. The DNA has the instructions which govern the cell function, shape, size, etc.
b) The cell membrane is the security guard. This cell component made of phospholipids, proteins, and carbohydrates protects all the fabric and decides what can get in or go out of the cell. Also, it is in charge of the communication with the environment and even, other cells.
c) Finally, workers reside in the cytoplasm, which is the space between the nucleus and the cell membrane. Here, all the tools and materials required for the cell to work, are found.
Cells with similar functions form tissues, which organize into organs. At the same time, different organs working together form systems (for instance, the digestive system) which, together, form your body.
In fact, there are about 200 different cell types building the human body. And, according to scientists, your body is made of approximately 4×1013 cells… that is around 40 trillion cells!
But, where do all those different cell types come from?
Every cell is derived from another cell (parent cell). When a cell divides, two new young cells are formed. A cell type can only give rise to cells of the SAME type, that is, a muscle cell will always divide into more muscle cells, a heart cell into heart cells, and so on.
So, how is it possible that our bodies are made of approximately 200 different cell types? Well, there are some undifferentiated cells, called STEM CELLS which have the ability to turn into potentially any kind of cell, given specific signals and conditions. Every stem cell is able to divide and generate more stem cells or to become a differentiated cell.
There are different types of stem cells. For example, as an embryo, we were a rich source of embryonic stem cells. As adults, we have a repository of tissue-specific stem cells, as the bone marrow stem cells. Given their potential to become almost any cell type, these cells have had a major impact in actual medicine.