Suprutural pupillary reaction

One of the key and most pressing problems of forensic science remains the diagnosis of the prescription of death. The attention of forensic doctors to this problem is not weakening, which is confirmed by the appearance of new scientific works devoted to establishing the prescription of the onset of death. Developed as a new way to diagnose the prescription of death at various times of the postmortal period, and modified previously known techniques. The need to continue research, develop new methods of diagnosis, and improve old methods is conditioned, in particular, by the existence of various ranges of postmortem periods: suprutal reactions; development of early cadaveric phenomena; the formation of cadaveric phenomena; development of putrefactive changes and other late cadaveric phenomena up to the complete skeletonization of the corpse. Accordingly, each of these periods develop principles and techniques for diagnosing phenomena that allow the prescription of death to be established. Analysis of modern scientific research shows that to date only the maximum aggregate of data on the prescription of death can provide a result, the accuracy of which meets the needs of law enforcement.

The most urgent task remains to determine the prescription of death in the early postmortem period, which accounts for a significant portion of the corpses at the scene. After the death of organs and tissues for some time can respond appropriately to various external stimuli. This phenomenon was called "suprutal reactions". During the period of suprutal reactions, a gradual physiological decay of the viability of individual organs and tissues takes place, irreversible changes develop and, finally, the death of individual cells (cell death) occurs; these processes correspond to different time intervals.

The duration of suprutinal reactions is determined by the typical accessory of tissues and a number of external conditions.

Certain possibilities in diagnosing the prescription of death in the period of suprutinal reactions give forensic practice the assessment of the pupillary response. This reaction consists in the ability of the smooth muscles of the iris to react to external stimuli by narrowing or dilating the pupil. One of the known ways of revealing this reaction is the effect on the smooth muscles of the iris of the eye of a chemical stimulus by the action of pharmacological preparations of atropine or pilocarpine by introducing them into the anterior chamber of the eye with a syringe, followed by fixing the reaction time of the pupils - their constriction or expansion. However, recent works devoted to the study of this suverital phenomenon were published in the 70-80s. Last century.

The aim of our work is to study the features of the anatomical and histological structure of the iris, the pupil sphincter and the dilator of the pupil, and their physiology in terms of the effect of modern pharmacological preparations regulating the size of the pupil.

Separately it is necessary to dwell on the anatomical structure of the eye, namely the iris, and the processes of regulation of the pupillary response in a living person. The iris, being the front part of the choroid of the eye, has the shape of a disk with a hole in the center and is actually a diaphragm that divides the space between the cornea and the lens into two chambers - the front and the back. The volume of the anterior chamber of the eye averages 220 μl, the average depth is 3.15 mm (2.6-4.4 mm), the diameter of the anterior chamber varies from 11.3 to 12.4 mm. From the anterior chamber of the eye, the surface of the iris is divided into two zones: pupillary, about 1 mm wide, and ciliary - 3-4 mm. The iris consists of two layers: mesodermal (anterior) and ectodermal (posterior). The pupil itself is an opening in the center of the iris, passing through which the rays of light enter the retina of the eye. Normally, the pupils of both eyes are round, the pupil size is the same. The diameter of the pupil in a living person varies on average from 1.5-2 mm to 8 mm, depending on the degree of illumination. The change in the diameter of the pupillary opening in a living person occurs reflexively in response to irritation of the retina with light, with accommodation, with convergence and divergence of the visual axes, in response to other stimuli. By regulating the flow of light entering the eye, the diameter of the pupil becomes minimal with maximum bright light and maximum in the dark. In fact, the pupil's response to changes in illumination is adaptive in nature, stabilizing the illumination of the retina, shielding the eye from excess light, reflexively dosing the amount of light, depending on the degree of illumination of the retina ("light diaphragm"). The change in the size of the pupil is due to the action of the sphincter muscle of the pupil (with the contraction of which the pupil narrows, miosis develops, and the muscles of the dilatator pupillae), with the contraction of which the pupil expands, mydriasis develops. Muscles are located in the iris of the eye in the mesodermal layer. In the pupillary zone (zone) there are circulating muscle fibers forming a pupillary sphincter with a width of about 0.75-0.8 mm. The sphincter muscle of the pupil has a telescopic type of contraction, its muscle cells correspond to all the criteria of smooth muscles (spindle shaped) and are oriented parallel to the pupillary margin. The bundles of muscle cells are tightly packed and separated by thin layers of connective tissue. Among the bundles of collagen fibers are distributed arterioles, capillaries, sensory and motor nerves. Nerves do not penetrate deep into a group of muscle cells, but adhere to their surface. In connection with this relationship of nerves and muscle cells, a number of researchers believe that groups of muscle cells form functional units. Apparently, only one cell of the functional unit is innervated, and dense intercellular contacts allow depolarization to spread to other cells. Basal membrane of the sphincter of the iris does not differ from the basal membrane of other smooth muscle cells. This membrane comes into contact with collagen fibrils separating the muscle groups, between which lie nerve fibers. In separate groups of muscle cells, nerves form bundles. Usually the bundle consists of 2-4 nerve axons surrounded by Schwann cells. Axons without a Schwannian membrane terminate directly on the muscle cell. The innervation of the sphincter muscle of the pupil is carried out by parasympathetic nerve fibers (postganglionic fibers) extending from the ciliary ganglion, acetylcholine acting on the M-cholinoreceptors is released from the endings of postganglionic fibers. Preganglionic fibers are part of the oculomotor nerve, starting from the pupillary neurons of the Yakubovich-Edinger-Westphal nucleus, which are part of the oculomotor nucleus of the brain stem. In the depth of the ciliary zone of the mesodermal layer there is a thin layer with a radial direction of the fibers - the muscle - the dilator of the pupil. The muscle cells of the pupil dilator are pigment epithelial cells and have the ability to form myofibrils in the cytoplasm, thus combining the characteristics of the cells of the pigment epithelium and smooth myocytes. The muscular dilator is innervated by sympathetic nerve fibers, postganglionic fibers depart from the upper cervical ganglion, norepinephrine and a small amount of adrenaline are released from their endings, which act on adrenoreceptors (alpha and beta); preganglionic fibers depart from the ciliospinal center located at the level of the eighth cervical, the first and second thoracic segments of the spinal cord.

After the onset of clinical death, first of all, the nervous tissue dies. The survival time, i.e., the time after which the renewal of blood circulation is not significantly reflected in the structure and function of the organ, for the brain is 8-10 minutes at a temperature of 37oC, but when the blood circulation stops in the body, this time interval decreases to 3-4 min, which is explained by the insufficient aeration of the brain due to the weakness of cardiac contractions in the first minutes after the resumption of blood circulation. In hypothermia in persons trained for hypoxia, the time interval may increase. At the end of this interval, the central nervous system can not exert any regulatory influence on the muscles of the pupil. Thus, intravital reactions of the nervous system remain fixed and preserved to various kinds of stimuli immediately preceding the onset of death, in particular anisocoria, ie, in fact pupils can posthumously display various intravital lesions of the nervous system. And the eye itself, in particular the muscles of the pupil, becomes an autonomous self-regulating structure. After the onset of death 1-2 hours later, the narrowing of the pupil begins (this is due to the constriction of the soft musculature of the iris against the background of the predominance of the sphincter of the pupil). Subsequent expansion is not observed, the intravital difference in the size of the pupils remains on the corpse, and with the postmortem narrowing of the pupils.

In fact, the substratum of the supratural reaction of the pupils is the experience of the smooth muscles forming the pupil's sphincter and the dilator of the pupil, and their preservation of the ability to perceive chemical stimuli, and to react accordingly, expanding or narrowing the pupil, ie, to fulfill the functions inherent in them for a living person. This reaction is akin to other suprutinal reactions, in particular, to supripital tissue stains, based on the preservation of the permeability of cell membranes with respect to vital dyes. An example is the eosin test, when there is a selective exclusion of "live" eosin cells by the membranes, and free penetration into "dead" cells, i.e., their staining. The marker of the experience of the smooth muscles of the pupil sphincter and the dilator of the pupil is their response to chemical stimuli - the pupillary reaction.

The influence is exerted only by local stimuli, in particular chemical substances acting directly on the smooth muscle cells. Such chemicals include pharmacological drugs used in ophthalmic practice.

To expand the pupil in ophthalmology, pharmacological preparations are used - myotics. These include two subclasses of drugs - M-holinomimetiki and anticholinesterase drugs. Anticholinesterase drugs have pronounced side effects, both local and systemic, and therefore are not used. Pharmacodynamics M-holinomimetikov consists in stimulation of M-holinoretseptorov smooth muscles of the iris, resulting in a contraction of the muscle-sphincter and develops miosis. M-holinomimetikami are pilocarpine, carbachol and acekledin.

For the dilatation of the pupil and the production of mydriasis, pharmacological preparations are used - mydriatica. This pharmacotherapeutic group - mydriatic and cycloplegic agents - includes drugs that have a similar pharmacological effect, but have different chemical structures and pharmacodynamics, which determine the realization of the final effect. This group includes cycloplegic mydriatica (M-cholinoblockers) and non-cycloplegic mydriatica (sympathomimetics). Pharmacodynamics of M-holinoblokatorov due to blockade of M-holinoretseptorov, which are located in the muscle-sphincter of the pupil, as a result of the passive dilatation of the pupil due to the predominance of the muscle tone-dilator and relaxation of the sphincter muscle. Distinguish M-holinoblokatory on the strength and duration of exposure: short-acting - tropicamide; long-acting - atropine, cyclopentolate, scopolamine, gomatropin. The pharmacodynamics of sympathomimetics, which exert a mydriatic effect, is caused by their agonism to alpha-adrenoreceptors, which stimulates and enhances their functional activity, which leads to an increase in the tone of the dilator muscle, as a result of which the pupil expands (mydriasis develops). Sympathomimetics include phenylephrine, mezaton, and irifrin.

The spectrum of pharmacological drugs used to assess the supratulatory pupillary reaction in the works of KI Khizhnyakova and AP Belov was limited to atropine and pilocarpine. The dynamics of the supripital reaction was established only for pilocarpine, the influence of environmental factors and causes of death was not taken into account. It seems promising to further study the reaction of the smooth muscle of the iris to chemical stimuli, namely, modern pharmacological drugs used in ophthalmic practice.

D. B. Gladkikh. Supripital pupillary reaction // International Medical Journal - №3 - 2012

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