What does "decomposition" begin with in human remains?

Decomposition begins with the breakdown of body tissues after death. This process is initiated shortly after the heart stops beating and blood circulation ceases, leading to a cascade of biochemical and physical changes in the body. As cells are deprived of oxygen and begin to die, they release enzymes that start to digest the tissues from within, leading to the breakdown of proteins, fats, and carbohydrates. This breakdown is aided by bacteria and microorganisms that were previously contained within the body, as well as those from the environment.

Other processes such as cooling of body temperature, preservation of organs, and swelling of body tissues may occur during the post-mortem phase but are not the starting point for decomposition itself. Instead, these processes can provide information about the time since death and the conditions surrounding it. However, the essential and defining characteristic of decomposition is the breakdown of tissues, establishing the foundation for later stages of decomposition and the eventual return of the body's components to the ecosystem.