A Basic Overview
If you haven't taken a biology class in high school or at least don't remember anything from it, this will be a small explanation of what skin is, along with a few simple tips to help you keep a little more blood inside your body (where it is supposed to be).
What Is Skin?
Skin is the single largest organ in the human body, serving as a protective layer for all of your more sensitive and vital squishy bits. It is divided into several layers, each serving a slightly different function. The outermost layer, the epidermis provides protection from contaminants in the environment, as well as providing a buffer zone between your nerves and any stimulus on the outside, so that touching something like a doorknob doesn't hurt like hell. Note that, by cutting through this, you are allowing free entry into your body to any contaminants that find their way in (sterilize everything). The epidermis, which is composed of keratinized epithelial tissue, doesn't actually contain any nerve endings or blood vessels. Instead, the layer just below the epidermis, the dermis (composed primarily of connective tissue, which anchor the epidermis to the tissue underneath), provides a fairly high nerve density, particularly in the regions such as the fingertips. In addition to this high nerve density, the dermal and hypodermal(the tissue below the dermis) tissues in this region are highly vascular (Lots of little capillaries and blood vessels), to provide the oxygen and nutrients needed to sustain the skin.
Where To Stick Things Into It
Since the epidermis itself is very thin, it would be a very bad idea to put anything on the border where the epithelial tissue ends and the connective tissue starts(The Basement Membrane). Why? Because if you were to accidentally hit the skin above or surrounding the implant, it could potentially force the implant back out of the skin, creating quite a mess, and less importantly, significant pain. In addition, it wouldn't be as comfortable as the second option. You can easily eliminate these problems by placing the implant a little deeper, in the connective tissue, which will grow back around the implant and bury it, giving it much more protection from impacts and stress.
Not Everything Should Be Cut
This is obvious. Pain can be mitigated by anesthetics (if they are legal where you live) or dealt with in a variety of ways, but there are many more problems than just pain. Cutting major blood vessels can be life threatening and passing out from lack of blood to the brain is absolutely terrifying (if a surgery gets to the point of passing out from blood loss, you need to reconsider your decision making paradigm). So make sure to know where those veins and arteries are. Getting even a basic understanding of where you shouldn't cut can save your life. Firstly, here is a very good website that will give you a visual representation if you are a more visual learner: https://human.biodigital.com/signin.html
Now, you can see most of the main arteries without anything more than a visual inspection. Smaller arteries that are still a concern can be found by shining a light into the area you're inspecting, as the skin and subdermal tissues are translucent. If there is a large blood vessel where you want to cut, find a different implant site.
Nerve dense areas are fairly easy to find, even if you don't already know most of them from personal experience. Implanting in these locations can have a significant effect on the functionality of your device, if it's haptic or sensory-based. Here is a basic list but there are plenty more which you can find just by touching the surface of the skin and seeing the difference of sensation as compared to the skin around it.
Some basic nerve dense areas (this is not a comprehensive list):
- pubis (for the love of science DON'T CUT here)
- webs between fingers
- anywhere on the face
- back of the head
- back of the hand
- bottoms of feet
- tops of feet
If you have any doubts about where you want to cut, do not cut there until you have received advice from a knowledgeable person.