Human decomposition

Decomposition is the process where the human body starts to decay the moment the heart stops beating and pumping blood around the body (cardiac arrest). Before the full process begins, the body passes through several stages.

Primary flaccidity
Immediately after cardiac arrest, all the muscles in the body relax, this is called primary flaccidity, and burning oxygen provides energy to keep the muscles tense when the body is still living, but once the body is dead, the energy cannot be provided due to the fact that it has stopped receiving oxygen. When the muscles relax, the sphincter will too, along with the bladder, ejecting urine and faeces from the body.

Algor Mortis (Death chill)
Algor Mortis, or the death chill begins immediately after death. On average, a deceased human body loses 1.5 degrees an hour until it reaches room temperature. Without a heart beat, blood and fluids will begin the lividity process.

Lividity (Livor Mortis)
Lividity begins when blood and fluids succumb to gravity and begin pooling the blood at the lowest points in the body. In light skinned people, pooling blood is visible outside of the body as a dark purplish blue and after a few hours, the blood clots. This is how forensic specialists can tell if a body has been moved.

Pallor Mortis
Pallor Mortis is the process of the blood draining from the veins and the body turning a shade of white. This is likely to occur in light skinned people.

Rigor Mortis
Rigor Mortis is when the muscles begin to stiffen after about 3 or 4 to 6 hours. This is because after death, calcium floods the muscle tissue and bonds with proteins that control muscle contraction, and the uncontrolled bonding causing the muscles to tense up for about 24 to 48 hours until the stiffening wares off. The eyes will cloud during this time, especially if they are left open. Once Rigor Mortis sets in, they are likely stuck open as the muscles in the body have tensed once again. According to one study, 63% of people fully close their eyes at death.

Secondary flaccidity
After the effects of Rigor Mortis have worn off, the muscles relax for the second time, and this is called secondary flaccidity.

Cell death
After the heart stops beating, the cells in your body stop receiving oxygen, but continue to function for a few minutes, generating carbon dioxide. Carbon dioxide is acidic, and when it builds up, it begins rupturing sacs inside the cells. The sacs contain enzymes that begin to digest the cells from the inside out. After the cells have died, they begin to decay due to necrosis. Without circulation, the dead cell matter cannot be cleared. As carbon dioxide builds up and the PH of the tissues in the body rise, the cells weaken and eventually their cell membranes break, releasing the inside fluids into the surrounding tissue. Enzymes in the fluid cause damage, blistering and colour changes.

Self-digestion/Putrefaction
Putrefaction is when oxygen has been depleted by the natural microorganisms in our respiratory and gastrointestinal system, and they begin to spread into other sections of the body. Enzymes in organs such as the pancreas cause it to digest itself, and bacteria from other deceased organs will help further digest the organ, or any other organs that are digested during the process, including the stomach, which turns the abdomen into a greenish colour. After about a week, bacteria and fungi will further digest or liquefy organs and muscles. Gas begins to build up, causing any non digestible waste to be ejected from the body. Two organic amine chemicals called Putrescine and Cadaverine are created during this interaction, and eventually, this makes its way into the blood vessels, resulting in them to reach other areas of the body and then exiting. Eventually, necrosis and the work of bacteria changes the colour of the skin to purple and finally black. The smell causes insects and other animals to invade the body, which has been happening already.

Bloating
Bloating is the process of gases building up in the body, causing the abdomen to expand after about 5 days. The gases will push out of any orifice.

Butyric fermentation
Butyric fermentation is the process of the organs and tissues drying and waxing over. During this period, the body’s skin will recede, giving the impression of growth. The tissues are being digested by more bacteria (Protozoa and Fungi) and insects. This stage takes about a year or more to be completed due to the changing of temperatures.

Post decay
Post decay is the stage where animals and plants digest remaining byproducts or the skeletal structure over the subsequent years since the decomposition.

Under and above ground decomposition
Underground, the body might take 8 to 12 years before it is reduced to its skeletal structure, but after about 50 years, even the bone mineral hydroxyapatite decomposes after the bone protein had long before it, but this event will only occur if the body is buried in high acidity soil with a PH of less than 5.3. Above ground, the body may decompose faster if attacked by plants, animals and bacteria that liquify the body.