After death, the body starts degenerating. Since the heart has stop working, there is no oxygen supply to all parts of the body. Cells start to die, body tempetature drops until it reaches room temperature. After some hours, there is a buildup of calcium in the muscle, this stiffens the muscles for some days. The stiffness of the muscles is known as Rigor mortis.
The muscles relax after several days and the stored feces and urine is expelled out of the body. The blood dries up causing the dead to look pale with red blotches all over. If the body is not attended to, the body begins to smell due to the release of chemicals from the body. Enzymes within an organ begin to digest the organ. Gradually, the body decays until nothing is left.