Which structure appears first in the order of appearance for rigor mortis?

Which structure appears first in the order of appearance for rigor mortis?

• A. Jaws
• B. Muscles of the eyes
• C. Chest
• D. Face and neck muscles

Answer: (A)

Rigor mortis starts in the small, highly active facial muscles because they run through ATP quickly after death, leading to early cross-bridge locking. The jaw muscles are among the most strongly active and are typically the first to lose ATP and stiffen, so they appear first in the sequence. While eye muscles can stiffen early as well, the usual timing taught places the jaw as the initial site, with facial and neck muscles following and larger muscle groups like the chest stiffening later.

Rigor mortis starts in the small, highly active facial muscles because they run through ATP quickly after death, leading to early cross-bridge locking. The jaw muscles are among the most strongly active and are typically the first to lose ATP and stiffen, so they appear first in the sequence. While eye muscles can stiffen early as well, the usual timing taught places the jaw as the initial site, with facial and neck muscles following and larger muscle groups like the chest stiffening later.