Thanatology is the science that deals with -

Thanatology deals with death in all its aspects. There is a progression from clinical death to brain death, biological death and then cellular death. Brain death follows clinical death which is due to lack of oxygen. First cerebral coex, then cerebellum, and then lower brain centres die. Thereafter the process of cellular death begins. Dr. Narayana Reddys Synopsis of Forensic Medicine & Toxicology 27th edition pg.66