The aim of this work was to study the structure of lung and hepatopancreas of Roman snail (Helix of pomatia of L., 1758). The study found that the lung occupies the lower turn of shell and presented by a saccate cavity, in the wall of that there are a kidney and heart with a pericardium, and also a rectum and ureter pass. An external surface of lungs covered by a shell and covered by an epidermis. An internal surface is covered by a flat ciliated epithelium and forms numerous folds in which pulmonary vessels and lacunae are accommodated. The branches of pulmonary vein have a thick muscular wall, that consists of circular and longitudinal muscular layers. An internal surface of lungs covered by the layer of mucus. Inhalation and exhalation are carried out due to reduction and relaxation of muscles of dorsal wall of the body that is named a “diaphragm”. Gas exchange occurs through the hemolymphatic capillaries of the lung wall. Respiratory motions take place not rhythmically, but through the different intervals of time depending on a requirement in oxygen. The frequency of pneumostome closing and opening is typically one time in a minute. At subzero humidity of atmospheric air of pneumostome closed by a mantle, and also one (or a few) epiphragms. The hepatopancreas (“liver” or liver gland) is in the upper rotation of the sink and formed by two parts: right and left, from which two liver ducts enter into the stomach respectively. The liver gland consists of many acinuss, surrounded by connecting tissue, that contains small number of muscular fibres. Calcium cells have a pyramidal form and usually do not reach the lumen of the acinus. Cytoplasm of calcium cells contains inclusions: grains of phosphoricacid lime and drops of fat. The digestive cells of the hepatopencreas are more elongated, often clavicular. Сytoplasm of digestive cells is loose and vacuolated and contain inclusions of yellow-green color. Enzyme cells on histopreparations are difficult to distinguish from digestive ones. They contain transparent vacuoles with a large round inclusion of yellow-green color, which consists of a cluster of several grains of different sizes. Hepatopancreas performs the following functions: secretory (enzyme cells), absorption and intracellular digestion (digestive cells), preservation of nutrients and calcium (calcium cells), and also excretory function.

The article presents data on the morphology of snakes and features of the pathomorphological study of representatives of this suborder of reptiles. There is also a brief description of the most common pathological conditions of reptiles, which are fatal without adequate veterinary care. Characteristic morphological features of snakes are described: a long narrow body, which is adapted for crawling, most of the internal organs are elongated, placed asymmetrically, some of them have lost their paired part. The skin of snakes is dry, almost devoid of glands, the outer layers of the epidermis form horny scales and shields. The snake's heart is three-chambered, three blood trunks independently depart from the ventricle separated by an incomplete septum: two aortic arches and the pulmonary artery, and the carotid arteries that supply arterial blood to the head and forelimbs depart only from the right aortic arch. Gas exchange occurs mainly in the lungs (in most snakes, the left lung is rudimentary) and the mechanism of respiration of the suction type. The digestive organs are elongated, and the liver is monocotyledonous. Metanephric kidneys provide isolation and water exchange. The body temperature of reptiles is not constant and largely depends on the ambient temperature (poikilotherm). Before the opening, the anamnesis is collected, and the type of reptile is determined. During the pathological examination, it is necessary to follow safety rules, especially when examining poisonous snakes. On external review, the skin is carefully inspected, attention is paid to the presence of ectoparasites (especially mites), remnants of the epidermis after the last molt, external damage, and so on. The mucous membrane of the oral cavity, teeth, external nostrils, cloacal slit are examined. To access the body cavity, a paramedial incision is made in the body cavity wall, bypassing large vessels. Internal organs should be discussed following the preservation of their anatomical and physiological relationships. In the process of pathomorphological examination, it is necessary to select material for histological, histochemical, bacteriological, virological, mycological, parasitological, and other types of laboratory tests to use a comprehensive approach diagnosis. Particular attention should be paid to diseases common to reptiles and humans (salmonellosis, leptospirosis).