Digestive System

DIGESTIVE SYSTEM, a more or less complex system of cavities lined with epithelium, which in certain parts is equipped with glands secreting various enzymes, by means of which the breakdown and dissolution of food materials occur, which are then absorbed through the walls of the same cavities. In more complex animals, the main part of the digestive system develops directly from the embryonic primary gut, i.e., from the endoderm, to which more or less significant ectodermal invaginations are then usually added, forming the initial and terminal sections of the intestinal canal. To the endodermal and partly to the ectodermal epithelium of the digestive cavity there is also added in all animals, starting from higher worms, a mesodermal cover with musculature and blood vessels. The digestive cavity communicates with the external environment through at least one oral opening, which occupies the place of the embryonic primary mouth (coelenterates and flatworms). In the vast majority of animals, however, the digestive cavity acquires the appearance of a tube opening in front with an oral opening and behind with an anal opening. The latter is formed anew in most invertebrates through the formation of an ectodermal invagination growing towards the posterior blind end of the gut and breaking through into the latter. In echinoderms and chordate animals, however, the anal opening develops at the expense of the embryonic primary mouth (blastopore), and the oral opening is formed anew in the form of an ectodermal invagination breaking through into the anterior end of the gut ("deuterostome" animals). The digestive cavity, which acquires the appearance of a tube stretching along the entire body starting from the higher worms, then differentiates into various sections. Among invertebrates, the differentiation of the intestine is most complex in higher mollusks (cephalopods) and in arthropods. In insects, only the midgut is endodermal, and consequently the ectodermal part here significantly exceeds the main part developing from the primary gut. To this it must also be added that the food entering the intestine is preliminarily ground with the help of complexly arranged mouthparts (jaws, mandibles, etc.), which are mainly transformed appendages. The differentiation of the intestine in chordates, including vertebrate animals, is peculiar. Unlike arthropods, almost the entire intestinal canal here turns out to be endodermal. A comparatively insignificant oral invagination leads to the formation of the anterior ectodermal section (stomodaeum), and an entirely negligible invagination at the site of the embryonic blastopore gives rise to the posterior ectodermal section (proctodaeum). In the adult state, precise boundaries between these sections cannot be indicated. The most characteristic feature of chordates is the transformation of a more or less significant anterior part of the intestine into a respiratory organ. Embryologically, the differentiation of the intestinal tract begins with the formation of an anterior, broader section, from which paired pouch-like outgrowths develop, growing in the direction of the outer integuments. These outgrowths then break through into small counter-invaginations developing from the ectoderm of the integuments, and thus communication of the anterior gut with the external environment is established through a series of so-called branchial pouches opening outward by gill slits. In this way, the organs of water breathing in lower vertebrates develop. In higher vertebrates, gill outgrowths also develop, marking out the pharyngeal region of the intestine, but they have importance here only as provisional formations. In front of the respiratory section lies a more or less capacious oral cavity (cavum oris), and behind it the intestinal tube narrows, forming the esophagus and its further, properly digestive parts. In the posterior part of the intestine in most vertebrates, urinary ducts and excretory pathways of the genital organs open. This part of the gut is called the cloaca. The intestinal tube differentiates behind the pharynx into several sections, differing both morphologically and in their function. The anterior, narrowed part of the tube is lined, like the sections lying in front, with stratified epithelium and constitutes the esophagus (oesophagus). Next comes the expanded and frequently curved section with single-layered glandular epithelium—the stomach (ventriculus, stomachus). The stomach is followed by the intestine proper, also lined with single-layered cylindrical glandular epithelium. In lower chordate animals, the entire intestine is lined with single-layered cylindrical ciliated epithelium. In cyclostomes, fishes, and amphibians, remnants of this ciliated cover are still observed in various places of the intestine. The wall of the intestine is thus composed of glandular cylindrical epithelium, covered on the outside by connective tissue with blood vessels (together forming the mucous membrane with the submucosal tissue of the intestine), and a muscular layer, usually consisting of an inner layer of circular fibers and an outer layer of longitudinal ones. The result of the activity of this musculature is the movements of the intestinal walls, or peristalsis, by means of which the mixing of the intestinal contents and its movement occur. The connective tissue and musculature of the intestine develop from the visceral leaf (splanchnopleure) of the lateral plate of the embryo. From the same source develops the outer cover of the part of the digestive tract lying in the abdominal cavity (part of the esophagus, stomach, intestine proper), the so-called serous membrane, which is nothing other than a part of the peritoneal lining of the abdominal cavity. Since this lining is formed due to the convergence along the midline of the visceral leaves of the paired lateral plates, it is natural that the intestine turns out to be fixed on the double leaves of the peritoneum—the dorsal and ventral mesenteries (mesenteria). The ventral mesentery mostly disappears, and the dorsal one is preserved in the form of the mesentery of the adult animal, suspending the intestine and supplying it with vessels and nerves. Associated with the digestive tract in vertebrates is a rather significant system of glands. In the oral cavity, variously differentiated salivary glands develop in land vertebrates. In the initial section of the intestine proper, two large and very important glands develop: in the ventral mesentery—the liver, and in the dorsal—the pancreas. In addition, in connection with the intestine in various vertebrates, there are also some other glandular organs (pyloric appendages of fishes, rectal gland, etc.) (see also Stomach, Teeth, Intestine, Cloaca, Esophagus, Pancreas, Mouth, Tongue). I. Schmalhausen. Statistics of digestive organ diseases. According to the international nomenclature of diseases and causes of death of the 1920 revision, the class of digestive organ diseases includes: diseases of teeth and gums; other diseases of the oral cavity and its appendages; diseases of the pharynx and tonsils; diseases of the esophagus; ulcer of the stomach and duodenum; other diseases of the stomach (except cancer); diarrhea and enteritis (at age under 2 years); diarrhea and enteritis (at age 2 years and older); ankylostomiasis; diseases from other animal parasites (except parasites of the eyeball and echinococcus of the liver); inflammation of the vermiform appendix (appendicitis) and inflammation of the cecum (typhlitis); hernia and intestinal obstruction; diseases of the anus and fecal fistulas; other diseases of the intestines; acute yellow atrophy of the liver; echinococcus of the liver; cirrhosis of the liver; gallstones; other diseases of the liver; diseases of the pancreas; inflammation of the peritoneum (peritonitis) without specification of cause; other diseases of digestive organs (except cancer and tuberculosis). Revised at the Paris Conference in 1929, as well as adopted in the USSR in 1930, the nomenclature of diseases and causes of death transferred ankylostomiasis, diseases from other animal parasites, and liver echinococcus into the group of infectious and parasitic diseases. The materials given below are based on the international nomenclature of the 1920 revision. Mortality from digestive organ diseases constitutes from 5% to 8% of mortality from all diseases in different states, with fluctuations for different years being comparatively small (Table 1). Table 1. Mortality from digestive organ diseases (per 100,000 population). Table 2. Mortality from digestive organ diseases in Germany per 100,000 population. [Note: Tables omitted in OCR/translation text]. A significant share, reaching in some countries almost half of all deaths from digestive organ diseases, is constituted by diarrhea and enteritis. A solid part of mortality from these forms of diseases falls on children under the age of 2 years. Thus, for example, in Czechoslovakia, out of 100,000 children under 2 years of age, 81 children died from diarrhea and enteritis in 1926, 82 in 1927, and 76 in 1928. Mortality from various forms of digestive organ diseases is higher in men than in women (Table 2).

The greatest share of mortality from diseases of the digestive organs, mainly from catarrh of the stomach and intestines, falls on infancy (up to 1 year); then mortality decreases and rises only in advanced and old ages (Table 3). In cities and urban-type settlements of the Byelorussian SSR in 1925, out of 100,000 population, 124 men and 100 women died from diseases of the digestive organs. In Moscow in 1926, out of the total number of deaths at the age of up to 1 year, 22.5% were due to deaths from diseases of the digestive organs. At older ages, diseases of the digestive organs are of lesser importance as a cause of death. Per 100,000 population in the same year, 159 people died from diseases of the digestive organs. In general, among all causes of death, diseases of the digestive organs occupy a prominent place. Morbidity from diseases of the digestive organs is best illustrated by the morbidity data for the city of Moscow and Moscow Governorate for 1926, since in this year (the year of the population census) a detailed processing of morbidity cards was carried out. Out of 1,000 illnesses in 1926, diseases of the digestive organs accounted for 224.7 cases in Moscow and 212.7 in Moscow Governorate. Per 1,000 population, the morbidity rate for digestive organs was 296.8 in Moscow and 237.6 in Moscow Governorate (Table 4). In the governorate, diseases of the stomach, round ulcer, acute gastritis and enteritis, and worms predominate. In men, both in the city and in the governorate, hernias and round ulcers sharply predominate; in women, worms, chronic gastritis, and appendicitis predominate. The high dental morbidity rate in Moscow should be attributed to the more developed network of dental care (resp. high utilization rate by the population). If one carefully examines Table 4, it can be seen that the age curve of each individual form of disease in the governorate almost exactly repeats the course of the curve for the city of Moscow. Thus, the maximum of dental diseases falls in both parts of the table on the age of 20-29 years, although the indicators of the upper half of the table, i.e., the city of Moscow...

2 times higher than the rates of the gubernia. Acute gastroenteritis shows its first peak at the age under 4 years, then drops sharply and rises again at 20-29 years, but much lower than the first time. The incidence rates of this form in the gubernia are much higher than in the city, especially at the age under 1 year. Proceeding from the average monthly incidence taken as 100, we obtain the distribution of diseases of the digestive organs by months, shown in Table 6. Table 6. Distribution of diseases of the digestive organs in Moscow and Moscow Gubernia by months. Month. Maximum diseases in the gubernia fall on July, and in Moscow on November and December. In the book «Morbidity of the population of Moscow and Moscow Gubernia,» Chertov writes: «This is explained by the fact that these months» (in Moscow) «account for the greatest number of cases of dental diseases and diseases of the pharynx and tonsils, making up a total of about 60% of all diseases of the digestive organs. Acute gastritis and enteritis fall on the summer months, especially July.» In the gubernia, where dental diseases give much lower rates, gastroenteritis prevails; its maximum also falls on July. Morbidity of the digestive organs with loss of working capacity yielded in the period 1925-1928 22.4 cases per 100 insured, with women having a slightly larger number than men (23.2 against 21.7). The index of days of loss of working capacity for that period was expressed by the number 195.6, also greater in women than in men (200.4 against 191.5). The connection of diseases of the digestive organs with production is illustrated in Table 5. The average duration of cases of loss of working capacity from diseases of the digestive organs is calculated at 8.8 days. Cases of stomach and duodenal ulcer (32.2) and hernia (38.3) give more than a month; the duration of a case of stomach diseases is 7.8 days, gastroenteritis lasts 5.7 days, dental diseases 4.5. Table 7. Disability from diseases of the digestive organs in Moscow by occupational groups (per 100 examined). Professions 1926 g. 1926 g. Employees..... All workers..... Including: Chemists....... Woodworkers . Builders ....... Food workers...... Metalworkers..... Leather workers..... Garment workers...... Textile workers . . . Printers..... Disability due to diseases of the digestive organs in Moscow in 1924 accounted for 2.1% of the total composition of those examined by the Bureau of Medical Expertise of the Disabled at an average age of 42 years, while women at an average age of 49 years accounted for 1.5%. Thus, despite the slightly higher morbidity with loss of working capacity in women, we find a lower percentage of disabled persons among them at a slightly older age. Workers show a disability from diseases of the digestive organs twice as high as employees. The maximum falls on chemists, woodworkers, and builders (Table 7).

Munixes. Occupational diseases of the digestive system. Some diseases of the oral cavity are of an occupational nature, caused by the action of industrial poisons and industrial dust (gingivitis), as well as prolonged mechanical pressure of an occupational nature on the teeth (see Teeth - occupational diseases). Industrial dust and poisons very frequently cause changes on the part of the stomach and intestines as well. The tension of the abdominal press associated with heavy muscular labor can serve as a factor leading to the formation of hernias. In addition, by increasing intra-abdominal pressure, changing the statics of the abdominal cavity organs, and causing significant shifts in the hemodynamic system and water-chloride metabolism, heavy muscular labor can lead to various disturbances of the secretory-motor function of the stomach, which, with already existing functional insufficiency of the stomach, can create a basis for the development of various catarrhal changes in some subjects. Another occupational factor has an important pathogenetic significance in this respect, namely, prolonged traumatization of the epigastric region caused by the pressure of various objects, in particular instruments (shoemakers, basket makers, office workers, etc.). Schmidt attributes an etiological role to this factor in the occurrence of ulcer processes, especially in cases where work is performed in a bent position, and Conheim even distinguishes so-called «ulcera decubitalia» into a special group, meaning by this stomach ulcers caused by prolonged pressure on the epigastrium. Various stomach diseases, both functional and often anatomical, can also be associated with the prolonged action of thermal factors. Not to mention intestinal lesions caused by industrial poisons (lead, mercury, arsenic), it is necessary to note various functional disorders that often occur in connection with the labor process. Thus, a prolonged forced sitting position accompanying certain types of occupational labor often leads to sluggishness of the intestine and constipation associated with it. On the other hand, occupational diarrheas can be observed. Such are, for example, summer diarrheas in workers of hot shops, occurring from abundant drinking of cold water. Occupational diseases of the intestines of a parasitic nature deserve attention. These include actinomycosis and helminthic disease, which is much more common, especially among slaughterhouse workers, fishermen, coal miners, and agricultural workers, the most frequent forms of which are ascariasis, trichuriasis, and taeniasis. Ancylostomiasis - see Ancylostoma, ancylostomiasis. Prophylaxis of occupational diseases of the digestive organs should proceed mainly along the lines of combating specific occupational hazards and general rationalization of production and everyday life. This is of particular importance in agriculture, the coal industry, and hot shops. In hot shops, a properly organized drinking regime is of great importance. The works of Marshak and Dukelsky (Central Institute of Occupational Health) showed the advantages of using weak solutions of sodium chloride (0.75%) for drinking in hot shops. A large role is also played by measures for the individual protection of workers (special clothing, respirators, etc.), preventing the entry of the harmful principle into the organism. Of no less importance is the well-established work of public catering establishments, especially canteens and buffets at the enterprise itself. In professions whose work is associated with a prolonged sitting-bent position, industrial physical culture is prophylactically important. Workers who come into contact with industrial poisons in their work should under no circumstances abuse alcohol, since the latter, among other things, is an excellent solvent for many industrial poisons, thereby contributing to the emergence of acute and chronic intoxications. B. Maravigovsky.