Which phrase accurately names the first muscle group involved in rigor mortis according to Nysten's law?

Which phrase accurately names the first muscle group involved in rigor mortis according to Nysten's law?

• A. The muscles of mastication
• B. The gluteal muscles
• C. The trapezius muscles
• D. The gastrocnemius muscles

Answer: (A)

Rigor mortis follows a specific sequence: it starts in the smallest, most active muscles and then spreads to larger ones. The facial region, especially the muscles used for chewing, are typically the first to stiffen. This makes the muscles of mastication the best name for the initial group affected. The reason is that these jaw muscles are relatively small and highly active before death, so their ATP is depleted earliest and cross-bridges lock in first. Larger muscle groups, like the gluteals, trapezius, or gastrocnemius, take longer to develop rigor mortis because they have more mass and delay in the accumulation of the conditions that cause stiffening.

Rigor mortis follows a specific sequence: it starts in the smallest, most active muscles and then spreads to larger ones. The facial region, especially the muscles used for chewing, are typically the first to stiffen. This makes the muscles of mastication the best name for the initial group affected. The reason is that these jaw muscles are relatively small and highly active before death, so their ATP is depleted earliest and cross-bridges lock in first. Larger muscle groups, like the gluteals, trapezius, or gastrocnemius, take longer to develop rigor mortis because they have more mass and delay in the accumulation of the conditions that cause stiffening.