What types of cells are there in the human body?
They’re mostly bacteria. That doesn’t sound particularly nice, but a lot of these bacteria are harmless, useful or even essential. I’m sure you’ve seen adverts for health drinks saying they have “friendly bacteria” in, or help the bacteria in our bodies. We form a symbiotic relationship with them: They live off us and get nutrition from our food, and in return they help us (not to be confused with parasites, who take nutrients from the host at the host’s expense) digest food, kill harmful bacteria, and so on. These bacteria are present within us from soon after birth. It might seem surprising that 90% (if that’s correct, since it’s not completely certain) of our body’s cells aren’t human, but since bacteria are so small they take up less space and have less mass. Of course, there’ll be some harmful bacteria in us as well though. As well as this there might even be a bit of fungi (as seen in fungal infections).
