How long does the pupil dilate after death

Update Date: 2022-01-19 Source: Network

summary

In addition to hypothermia and stiffness, mydriasis is the second criterion for determining death. One of them is brain death. Some people also have this phenomenon when they are in a deep coma. Now let's take a look at how long the pupil dilates after death.

How long does the pupil dilate after death

First, the pupil is mainly controlled by two groups of muscles: the sphincter of the pupil, whose contraction causes the pupil to shrink; the dilator of the pupil, whose contraction causes the pupil to expand. The pupillary sphincter is innervated by the third pair of oculomotor nerve (belonging to parasympathetic nerve), and the pupil dilator is innervated by sympathetic nerve. After death, the brain activity stops and the brain nerve stops exciting (that is, the parasympathetic nerve function drops), which leads to the sympathetic nerve function being shown, that is, the pupil is opened.

Second: the pupil dilation after death is one of the manifestations of brain death, the pupil dilation and the disappearance of light reflection; after death, the pupil dilation and fixation are often used as an important test content to judge death. Specifically, it means that if the pupil diameter is greater than 5mm, the pupil size will not change when a flashlight is used to irradiate the eyes (the pupil will shrink during the prenatal examination).

Third: for some reasons, such as poisoning, resulting in pre life pupil narrowing or dilation, generally speaking, these signs will disappear after death. There is only one exception. After the death of organophosphorus poisoning, the signs of narrowing pupil will be preserved, which is also a characteristic of this kind of poisoning. After about eight minutes, the pupils dilate.

matters needing attention

Mydriasis is not completely a phenomenon that all people will appear after death. Some people, such as a car accident, will appear the symptoms of pupil narrowing. But people who die normally have dilated pupils. It's all after brain death.