The observation of a single tear at the moment of death, often called the “last tear,” is a powerful cultural image. This phenomenon, known scientifically as terminal lacrimation, is rooted in biology, not emotion. It is not a conscious emotional response but rather a result of the body’s physical systems shutting down. Understanding this event requires examining the mechanics of tear production and the specific physiological changes that occur as life ends.
The Physiology of Human Tears
The human eye produces three main types of tears, each serving a distinct purpose and having a slightly different composition. Basal tears are secreted continuously to keep the eye lubricated, protected, and nourished, forming the constant tear film over the cornea. Reflex tears are produced in large volumes to wash away irritants, such as dust or strong odors, and are triggered by sensory nerves on the eye’s surface. Psychic tears, those associated with strong emotions like sadness or joy, involve hormone release and activation of higher brain centers.
The lacrimal apparatus, responsible for managing this fluid, includes the lacrimal gland for production and a complex drainage system. Tears flow across the eye and drain through small openings called puncta, which lead into canaliculi, the lacrimal sac, and finally the nasolacrimal duct that empties into the nasal cavity. In a healthy state, the drainage system efficiently manages the basal tear rate, preventing overflow.
Terminal Body Changes Leading to Lacrimation
The immediate cause of a tear at the end of life is largely a failure of fluid management and the persistence of a primitive nerve reflex. As the body enters the terminal phase, general systemic dehydration occurs due to reduced fluid intake and metabolic changes. This dehydration can cause the eyes and mucous membranes to become extremely dry, triggering a protective response.
The sensory nerves on the corneal surface, mediated by the trigeminal nerve, send signals to the brainstem. This initiates the trigeminal-parasympathetic reflex, which commands the lacrimal gland to produce a sudden, protective surge of reflex tears. This reflex is one of the more primitive and robust, often remaining functional even as higher cortical activity declines.
Simultaneously, the muscles that control the tear drainage system begin to lose their tone. The orbicularis oculi muscle normally contracts during blinking to actively pump tears from the eye into the nasolacrimal duct. As muscle control relaxes, this active pumping mechanism fails, and the puncta can no longer draw fluid away effectively, allowing even a small amount of tear fluid to pool on the eye’s surface.
Why Lacrimation Can Be a Final Observable Event
The tear fluid becomes visible because major systemic functions have ceased. The cessation of circulation and respiration are internal events, but the fluid pooling on the eye is an external, visible change, making the tear droplet highly noticeable for observers. This subtle, localized fluid release is often among the final observable movements, along with muscle twitches or gasping breaths, because the brainstem controls many of these basic, non-voluntary reflexes. The persistence of the brainstem-mediated lacrimal reflex, combined with the relaxation of the drainage muscles, causes the fluid to spill over the eyelid, giving the physiological event the appearance of a conscious, final action.