Morphology of the Human Olfactory Analyzer

The sense of smell provides people with valuable information about the biochemical environment and their own body. Olfactory disorders occur in pathologies of the nasal cavity, liver cirrhosis, psychological and endocrine diseases. Smell affects various psychological aspects of people's lives, forming positive and negative emotional memories associated with smells. With the dysfunction of the olfactory analyzer, a person will not do the analysis whether the food is good, will not be able to feel the presence of poisonous gases in the air, bad breath. This puts a person in an awkward position and increases the risk of social isolation. The purpose of the study was to highlight the components of the normal structure and functioning of the human olfactory analyzer. Identification of odors in the environment and from one's own body is provided by the olfactory analyzer. Primary odors as camphor, floral, fruity, spicy, tarry, burnt and putrid in different quantities form secondary odors. Aromas are composed of volatile molecules called odorants. The smallest amount of odorant that causes an odor sensation is called the odor threshold. In people with coronavirus disease the sense of smell temporarily disappears (anosmia); it is reduced (hyposmia) in liver cirrhosis and rhinitis, and in Alzheimer's disease and schizophrenia besides hyposmia there is olfactory hallucination (phantosmia). Olfactory dysfunction adversely affects children's cognitive abilities. Fragrances change emotions and behavior. Aromas are used to regulate the physical and psychological state of the patient. Volatile molecules of fragrances penetrate through the layer of mucus that covers the olfactory epithelium located in the olfactory region of the nasal mucosa. The olfactory epithelium consists of olfactory, supportive and basal epitheliocytes, as well as secretory cells of the olfactory glands. Olfactory cells are modified nerve cells that have a body, an axon, and a dendrite, which ends with a receptor in the form of olfactory cilia. Volatile molecules interact with the olfactory cilia and then with the receptor protein, which is located on the olfactory cell bodies. In humans, olfactory cells have 350 receptor proteins. One type of receptor can register molecules of several different odorants. Molecules of the same odorant can activate several different receptors simultaneously. The nerve impulse from the olfactory cells (bodies of I neurons) reaches the nerve cells (bodies of II neurons) of the olfactory bulbs via their central outgrowths (olfactory filaments). Axons of nerve cells of olfactory bulbs continue to bodies of III neurons, which are located in subcortical centers of the brain (almond-shaped body, nuclei of the transparent septum). In human, to analyze a particular odor, axons from bodies of III neurons continue to cortex, namely to the area of the uncus of the parahippocampal gyrus

MODERN CONCEPTION AS TO THE FUNCTIONAL MORPHOLOGY OF THE OLFACTORY SYSTEM AND ITS CHANGES UNDER THE INFLUENCE OF SOME EXOGENOUS POLLUTANTS

The interaction between a body and an environment provides the main aspects of human life. The study of the functional structure of the olfactory analyzer plays an important role both in clinical and in experimental studies, but the question of its features in humans needs detailed research. The paper presents the modern data of the structural and functional organization of the olfactory analyzer. Particular attention is paid to the structural organization of olfactory bulbs as most complicated and least studied component of the olfactory analyzer. The morphological and functional changes of the olfactory analyzer are developing in some diseases and in action of adverse environmental factors are described while the accentuation is placed on the differences of the mechanism in the pathogenesis of damage to the olfactory analyzer, depending on the nature of the influence of pathogenic factors. In this way as the result of short-term intense effects of the pollutant, irreversible atrophic changes are primarily affected to the olfactory epithelium, thus, to some extent, preventing the spread of the toxin to other analyzer structures. Conversely, a long-term exposure to low doses usually retains the functional activity of the olfactory epithelium, while harmful substances penetrate the central unit of the olfactory analyzer. In such cases, the olfactory dysfunction can be diagnosed after a long time after the start of the cohort with certain pollutants. Currently, studies of the influence of exogenous toxins on various parts of the olfactory analyzer on animal experimental models are quite active. At the same time, the issue of functional and morphological changes in various structural components of the human olfactory analyzer under the influence of negative environmental factors remains poorly understood and requires further morphological and biochemical studies, in order to be able to further develop effective therapeutic and prophylactic means.

The Influence of Fixatives on the Validity of Histological Preparations of Olfactory Organ in Teleostei

The olfactory system of fishes plays an important role in reproduction, migration, and feeding. When studying the morphogenesis of olfactory analyzer in fishes, it is crucial to determine the exact time at which the placode, olfactory pit, and olfactory lamellae are formed. Among a large number of fixatives, 10 % formalin and Bouin’s solution are most commonly used to study the olfactory organ of Teleostei. Use of inappropriate fixative or incorrect fixation process can damage the structures under investigation and, as a result, will lead to the misinterpretation of results. The influence of the fixatives on the preservation of olfactory structures of European weather fish Misgurnus fossilis (Linnaeus, 1758) as close as possible to their living state is studied. Similar stages were fixated in Bouin’s solution as well as in 10 % formalin. Histological preparations for the light microscopy were made using the standard histological methodologies. At all analyzed stages of European weather fish development, histological preparations are more accurate, reliable, and informative aft er the fixation in Bouin’s solution. Aft er the fixation in 10 % formalin, it is impossible to determine the moment at which the olfactory pit begins to form. Because of the artifacts of olfactory epithelium appearing aft er fixation in 10 % formalin, the timing of olfactory lamellae formation could be easily misinterpreted and a comparative analysis on the morphogenesis of the olfactory analyzer becomes more complicated. Given our observations, a thorough revision of previous literature has to be performed to derive accurate evolutionary and morphological interpretations.

The Development of Olfactory Organ of Lissotriton Vulgaris (Amphibia, Caudata)

The Development of Olfactory Organ of Lissotriton vulgaris (Amphibia, Caudata). Kovtun, M. F, Stepanyuk, Ya. V. - Using common histological methods, the morphogenesis of olfactory analyzer peripheral part of Lissotriton vulgaris (Amphibia, Caudata) was studied, during the developmental period starting with olfactory pit laying and finishing with definitive olfactory organ formation. Special attention is paid to vomeronasal organ and vomeronasal gland development. Reasoning from obtained data, we consider that vomeronasal organ emerged as the result of olfactory epithelium and nasal cavity differentiation.