There’s a delicious carrot salad I occasionally make. It’s called “Korean carrot,” although the provenance of this dish is most likely Russian. In any case, this garlic and vinegar-laced concoction requires grated carrots; and as I was grating the carrots earlier today, I managed to grate into my finger as well.
This got me thinking about the interesting activity that happens in your skin when you get a cut and how this activity changes over time as the cut heals.
The human skin is the largest organ in the body, and a crucial one at that. It serves as a multi-layered barrier between our internal organs and the external, pathogen-filled environment; it helps our bodies regulate temperature and retain necessary moisture and nutrients that would otherwise wash away. Thus when the skin gets penetrated via a scrape or a cut (or other kind of wound), all defence systems in the skin are go.
So this is what happened on my thumb today when I grated a bit of skin off. The tiny blood vessels around the cut, also known as capillaries, immediately constricted to minimise the bleeding. A torn blood vessel leaks certain enzymes that trigger platelets to rush to the scene and clump together; these cell fragments banded together with proteins in the blood that cause coagulation, and soon the bleeding stopped. Next up, white blood cells, responsible for fighting infection, came to the rescue through the previously constricted blood vessels, and made the emergency site go swollen and leaky. Inflammation is good, it means the white blood cells are doing their job.
After all infection threats are eliminated, the cut will start to heal properly by forming a matrix of new cells across the wound — new capillaries will emerge, needed for bringing oxygen and nutrients to the disaster zone so that proteins, particularly collagen, can be produced. Collagen will support the restorative process and help thicken the skin around the edges of the cut, so that it can stretch over the wound and eventually form a brand new layer of skin. If a scar remains, the tissue in it will be mostly residual collagen, which is exactly what gives scars their characteristic white appearance.
Meanwhile, there is not much else I can do but to make sure I get enough vitamin C which is needed to produce collagen, keep the cut clean and try to limit immersion in water. The last one is mostly due to the pain. You know that terrible stinging you experience when wounds are exposed to water? That’s because without the skin there to protect them, the underlying cells which are surrounded by a semi-permeable membrane, are easily messed up upon contact with a liquid that has a lower electrolyte content than the cell contents themselves. In other words, unless the water has a certain concentration of salt in it, the cells exposed to it go out of whack and swell up or even burst. Ouch.