human skin
Posted by cat hopson on March 29, 2006
Q: Why does putting a needle through the outer layer of skin cause no pain or bleeding?
A: Good question and one I used to wonder about too. When I was young, my father used a sterile needle to release the fluid in a very large blister that I had on my foot. I was convinced it would hurt a lot, but felt nothing. Boy, was I relieved. When I asked why it didn't hurt he told me that the upper layer of skin has no nerve endings so there was no way for me to feel pain. Neat! There are no nerves or blood vessels in the upper layer (called the epidermis). So, you can insert a needle into the epidermis and never feel a thing and not bleed. Of course, if you jab the needle in a wee bit too deep and get it into the dermis (next layer of skin) you will definitely feel it and it might bleed too - there are nerves and blood vessels in the dermis. Thanks for asking.
John Wiessinger ( March 30, 2006)