Decomposition starts almost immediately after death, but certain cells decompose as different rates. While brain cells begin dying within minutes of death, skin cells can continue to operate for many hours. Rigor mortis quickly sets in and lasts for roughly 24 hours. Without a beating heart, gravity begins drawing blood to pool on the underside of the corpse, making the exposed cadaver appear white and wax-like, while the underside (the side touching the ground) looks bruised and black. For this reason, many morticians will lift the head and place it on a pillow to prevent discoloration of the face and neck. If the body is not embalmed, the skin will begin to turn blue in color and then blacken within 8 - 12 hours.

Without an active immune system, the microorganisms found throughout our GI tract multiply unabated and quickly begin devouring our the organs associated with digestion. As they break through the intestines, a green patch will appear on the skin and a greenish, sometimes blistering path appears on the abdomen. As the bacteria eats its way out of the intestines, it spreads to the chest and down the thighs. At this point, the cadaver begins to smell incredibly foul. Not only are our own enzymes (such as stomach acid) aiding in the rotting process but the bacteria have generated a great deal of hydrogen sulfide gas. This gas will push the intestines out of the rectum and the tongue from the mouth.

Undertakers work to preserve the body the best they can. They can suck the gas from the cadaver using a hollow needle and they will apply makeup to the departed's face, neck and other exposed areas of skin (such as the hands). Blood is drained from the cadaver from a large artery or the heart itself while embalming chemicals are then pumped through the cadaver's veins. Formaldehyde and the various other chemicals used by morticians to embalm bodies work to either kill, deter or slow down the bacteria and arthropods responsible for decomposition. It also firms up the tissues in the skin and muscles, temporarily preserving the countenance and physique of the departed. The embalming process is not permanent and is meant mostly for the benefit of funeral visitors.

Preservation is very much dependent on quality of embalming, type of burial, type of casket, climate and even the lifestyle of the deceased (such as emaciated vs. obese upon time of death). Warmer temperatures will accelerate the rate of decomposition while colder temperatures and drier climates tend to slow the rotting process. Embalmed bodies exhumed after five years showed little decomposition aside from mold growing on the skin. In good conditions, embalmed bodies can last for decades, sometimes even hundreds or even thousands of years, such as Incan and Egyptian mummies. Rosalia Lombardo, who died nearly 100 years ago, still looks mostly intact though has began to show signs of decomposition such as sagging skin.

Without exposure to decompositional organisms, the skin can remain mostly intact. While some claim that hair and nails continue to grow after death, it is actually just the skin drying out and revealing more of the follicle and nail bed.

OPEN AIR: Though you have specified that the body be buried, these images of rotting pig carcass (NSFW) are useful to see the stages of decomposition when left to its own devices. Pigs are similar anatomically to us in many ways in terms of their organ systems, including a soft, mostly-hairless skin.