What happens when a nail goes into your skin

A high-level illustration of how your body responds to damage, and where that redness and swelling comes from. An engaging 14 minutes from Khan Academy:

https://youtu.be/FXSuEIMrPQk

• Killed and damaged cells release chemical markers (chemokines).
• Mast cells are activated by bacteria, chemokines or physical damage, to release histamine.
• The histamines causes the capillary cells to move and expand the capillary (vasodilation), and the wall becomes more porous.
• Neutrophil (a kind of white blood cell) can now get through to the damaged area and start eating up bacteria and damaged cells.
• Dendritic cells start chomping on viruses.
• B-cells and T-cells start moving in… it’s getting crowded!