PBS 122 Changes After Death PDF

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Changes After Death

PLTW Biomedical Science Principles of Biomedical Science

Changes After Death Even after death, the body continues to tell a story. Predictable changes occur in the first few hours and days postmortem, or after death. These changes can be used as clues— clues that help an investigator estimate when a person most likely died. Let’s explore some of these changes! Within the first several hours after death, the corneas, which are usually the clear parts of the eyes, become milky or cloudy. Immediately after death the body begins cooling (or heating) to match the temperature of the body’s surroundings. This postmortem change in body temperature is referred to as algor mortis. Body temperature typically reaches the temperature of the surrounding environment within 24 hours of death. It’s estimated that a body loses (or gains) 1.5 degrees per hour. But it’s usually not that simple. External factors, such as room or air temperature, exposure to sun, wind, or snow, or the clothes a person is wearing, impact this estimate and can make it challenging to pinpoint an exact time of death. After the body stops functioning, the muscles contract and stiffen. This change is called rigor mortis and typically begins 2–4 hours after death. Rigor is first observed in the head and neck and then moves to the arms and legs. Full rigor is present throughout the body in 8–12 hours and “fixes” the body in the position assumed at death. After about 36–48 hours, rigor fades as decomposition begins. When the heart stops beating, the blood is at the mercy of gravity. Blood settles or collects on the parts of the body facing the ground. The bluish color seen on the skin where this blood pools is called livor mortis or lividity. Early signs of this blood settling occur within the first 2 hours of death. Full signs occur within 5 hours and lividity is fixed in place in 8–12 hours. Decomposition begins 36–48 hours after death. The body turns greenish in color and may swell or bloat as bacteria break down tissue and release gas. This decomposition, or putrefaction, also comes with a nasty smell. Insect activity can also provide clues about how long a person has been dead. The presence of eggs, larva, or full-grown bugs provide a timestamp for how long the body has been decaying.

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