What causes postmortem lividity?

• A. Cooling of the body
• B. Gravitational settling of blood
• C. The necrosis of tissues
• D. Cellular apoptosis

Answer: (B)

Postmortem lividity, also known as hypostasis or postmortem hypostasis, occurs due to the gravitational settling of blood in the body after the heart has ceased to pump. When circulation halts, blood begins to pool in the dependent (lower) parts of the body due to gravity. This pooling causes a purplish discoloration of the skin and tissues in those areas, which is essential for forensic assessments and understanding the timing of death.

The pooling is a direct consequence of the cessation of blood flow, leading to a lack of oxygen and subsequent changes in the red blood cells, which become trapped in the capillaries and give rise to the characteristic color. This process typically begins within 30 minutes to 2 hours after death and continues for several hours, depending on environmental conditions.

Cooling of the body, necrosis of tissues, or cellular apoptosis can occur after death but are not the main mechanisms underlying postmortem lividity. The cooling of the body, known as algor mortis, refers to the decrease in body temperature, while necrosis and apoptosis refer to cellular death processes that occur at a different biological level and do not directly involve the pooling of blood, which is the hallmark of lividity.