Some people think that the human body is an extremely complex structure and system, beyond the understanding of the average person. While it is indeed complex and has a lot of parts to it, this isn’t necessarily true. Anyone could understand the human body and its systems if they were to liken it to a machine.
We usually consider machines to be less intimidating because we are the creator of those machines, after all. Well, the human body is just another machine, just it is organically composed, instead of being made out of metal.
Let’s take the circulatory system. It functions like a plumbing system. A pump (the heart) pushes the blood around the body. It passes through a filter (the liver) and special additives are put into the blood (oxygen via the lungs) as it circulates. And that’s really all. There are certain pipes (veins and arteries) that are more important than others as they supply fluid to more sensitive systems. See? Not all that complicated.
Or how about the digestive system. This is really like a processing plant. Raw materials enter in and are broken down first by being crushed (the mouth) and then are left in a vat of acid (the stomach). Once broken down, special filters extract valuable elements from the material (the intestines) before the waste is excreted. Again, just a simple system.
Understanding the various parts of the human body should be done one at a time to ensure that a firm understanding of a single system is achieved before trying to tackle other ones. There are plenty of books, videos, anatomy models, and other aids that can be employed to help increase your understanding of how these systems work.
A working knowledge of the various systems will make anyone more adept at applying first aid.