why does rigor mortis start at the head
Rigor mortis At the time of death, a condition called "primary flaccidity" occurs. Following this, the muscles stiffen in rigor mortis. All muscles in the body are affected. Starting between two and six hours following death, rigor mortis begins with the eyelids, neck, and jaw. The sequence may be due to different lactic acid levels among different muscles, which is directly related to the difference in glycogen levels and different types of muscle fibers.
Common carotid artery In anatomy, the left and right common carotid arteries (carotids) (English: /kəˈrɒtɪd/[1][2]) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.[3][4]