According to Nysten's Law, rigor mortis begins with the muscles of mastication and progresses downward, ultimately affecting the legs last. This statement is:

• A. True
• B. False
• C. It begins with the limbs first
• D. It affects the chest first

Answer: (A)

Rigor mortis follows a predictable head-to-toe progression, starting in the small, highly active facial muscles used for mastication and expression, and then moving downward to the neck, trunk, and finally the limbs. After death, ATP is no longer available to allow muscles to relax, so cross-bridges form and muscles stiffen in the order determined by muscle size, activity, and energy use. Because the facial and jaw muscles are small and metabolically active, they lose the ability to relax first, so rigor appears there first and then spreads down the body, with the legs being last to stiffen due to their larger mass and slower onset. The statement aligns with this sequence, so it is true. Choices proposing that rigor starts in the limbs or chest first contradict this established pattern.