system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a cut heal? Do the cells around it just replicate until they fill in the hole?
gpt
When your skin cells break they still behave (relatively) normally. Blood is what fixes the wound. The first response to a cut is called the coagulation cascade. Basically blood enters the cut region and clots the site with platelets and fibers called fibrin. It forms a scaffold for new cells to fit in, which release growth factors and other proteins to pull specialized cells to the wound site. Over time, these specialized cells pull fibrin together with collagen and form the extracellular matrix that was broken. The cells stuck in the matrix release proteins due to lack of oxygen (hypoxia) that starts angiogenesis (growth of new veins and arteries) allowing for capillaries to grow into the matrix to ensure cells receive oxygen and nutrients. Within this matrix are embedded cells, but at a lower concentration than regular skin. The blood is only focused on fixing the cellular matrix so it sort of overdoes it, forming a scar. Mechanical stability of the wound doesn't reach about 70 percent until a month later and never reaches 100% relative to original skin. This process is more specialized and extremely interesting, with different pathways and mechanisms to form clots.