Which statement is true regarding the onset pattern according to Nysten's law?

Which statement is true regarding the onset pattern according to Nysten's law?

• A. It begins with the muscles of mastication
• B. It begins with the leg muscles
• C. It begins with the back muscles
• D. It begins with the abdominal muscles

Answer: (A)

Rigor mortis follows a specific sequence after death, and Nysten's law says it begins in the muscles of mastication—the jaw muscles. These small facial muscles have high metabolic activity and are among the first to exhaust ATP after death, so actin-mactosin cross-bridges lock and the muscles stiffen early. From there, the stiffening spreads in a stepwise fashion to the neck, then the trunk, and finally the limbs. So the statement that it begins with the muscles of mastication is the best fit because it names the initial site of onset in this orderly progression.

Rigor mortis follows a specific sequence after death, and Nysten's law says it begins in the muscles of mastication—the jaw muscles. These small facial muscles have high metabolic activity and are among the first to exhaust ATP after death, so actin-mactosin cross-bridges lock and the muscles stiffen early. From there, the stiffening spreads in a stepwise fashion to the neck, then the trunk, and finally the limbs. So the statement that it begins with the muscles of mastication is the best fit because it names the initial site of onset in this orderly progression.