First Organ Affected by Rigor Mortis

The organ which is quickly affected by rigor mortis, usually within one hour of slaughter, is:

Correct Answer: Heart

The Heart is the first organ to enter rigor mortis, usually within one hour of slaughter. This is because cardiac muscle has one of the highest metabolic rates and ATP turnover, so its ATP reserves are depleted most rapidly after death.

Why the Heart First?

• The heart contracts ~70 times per minute during life — it has a very high ATP demand.
• After death, oxygen supply stops but the heart muscle continues trying to contract, rapidly depleting ATP.
• Once ATP is gone, acto-myosin bonds lock permanently → rigor mortis sets in first in the heart.

Rigor Mortis in Different Tissues

• Heart: within 1 hour (fastest).
• Skeletal muscles (large): 6–12 hours post-slaughter.
• Resolution: 24–72 hours, depending on temperature.

Clinical Significance

• Rigor mortis is used in forensic science to estimate time of death.
• In meat science, the stage of rigor determines tenderness and water-holding capacity of the meat.