Final answer:
Medical needles are engineered to penetrate the skin with less resistance by having a sharp, smooth tip and are sometimes coated with lubricants. The reduction of dry skin resistance when the skin is wet and the low resistance of internal bodily fluids facilitate needle insertion.
Step-by-step explanation:
The student's question refers to the mechanisms that allow needles to penetrate the skin with reduced resistance. Needles designed for medical purposes are often coated with lubricants or have been engineered with a fine, sharp, and smooth tip that minimizes friction when inserted into the skin.
One of the principal factors that facilitate smooth insertion is the reduction of dry skin resistance, which is a natural barrier that typically offers higher resistance to penetration. When skin is wet, the presence of salts which go into ion form significantly lowers skin resistance. Additionally, once the needle bypasses the skin barrier, the resistance drops further due to the body's internal environment, which is rich in ionic solutions and bodily fluids that have low electrical resistance, allowing for more accessible passage.
Intravenous needles and other medical inserting devices must contend with these factors of skin resistance and body's internal fluid dynamics to ensure a smooth and less painful entry for medical procedures.