|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
MOST IMPORTANT SCIENTIFIC DISCOVERIES
Physiology of the digestive system. History and essence of scientific discovery
Directory / The most important scientific discoveries The works of the Russian scientist are recognized as truly classic Ivan Petrovich Pavlov on the physiology of digestion. This applies as much to the value of the actual and theoretical results as to the originality and skill of execution. Thanks to the genius of Pavlov, it was possible to bring the physiology of the digestive tract organs out of a dead end and raise it to an unprecedented height. “Before Pavlov, the physiology of digestion was one of the backward sections of the science of physiology in general,” notes E.A. Asratyan in his book on the physiologist. “There were only very vague and fragmentary ideas about the patterns of work of individual digestive glands and the entire digestive process as a whole. Vivisectionally acute experiment - the main method of studying the functions of the organs of the digestive system at that time turned out to be unsuitable for revealing the secrets of the work of these organs.Moreover, the actual results obtained with such vicious experiments caused many errors, for example, the idea that the gastric and pancreas do not have secretory nerves (Heidenhain , Starling, Beilis, etc.) If individual scientists were able to establish the presence of secretory nerves for other digestive glands, for example, for salivary glands (Ludwig, Claude Bernard, Heidenhain, Langley, etc.), then this rough method of physiological research is still not made it possible to reveal all the subtleties of the nervous regulation of their functions. Knowing this, many of our and foreign scientists (Claude Bernard, Heidenhain, Basov Thiry, and others) tried to replace vivisection with a more perfect method of research - experiments on chronically operated animals. However, these attempts were not crowned with due success: either the performed operations turned out to be of little value in terms of design and implementation technique (fistula of the ducts of the salivary glands by Claude Bernard, isolated stomach by Heidenhain), or cleverly conceived and successfully performed operations were insufficient to identify the patterns of the work of this organ, although would be in general terms and suitable only for obtaining separate, disparate facts about their work. Without exaggeration, we can say that science owes the main and most reliable information about the physiology of the digestive glands to Pavlov. He actually re-created this important chapter of physiology, created a monolithic and integral doctrine of a single digestive process instead of the previously existing formless mixture of unrelated half-hearted and erroneous information about the work of certain organs of the digestive system. None of the Russian scientists of that time, even Mendeleev, did not receive such fame abroad. "This is a star that illuminates the world, shedding light on paths not yet explored," HG Wells said about him. He was called "a romantic, almost legendary personality", "a citizen of the world". Ivan Petrovich Pavlov (1849–1936) was born on September 26, 1849 in Ryazan. His father, Peter Dmitrievich, was a priest. From early childhood, Pavlov took over from his father perseverance in achieving goals and a constant desire for self-improvement. At the request of his parents, Pavlov attended the initial course of the theological seminary, and in 1860 he entered the Ryazan Theological School. In his father's extensive library, Ivan somehow found a book by G.G. Levy "Physiology of everyday life". The book so deeply sunk into his soul that, as an adult, "the first physiologist of the world" at every opportunity quoted whole pages from memory. Fascinated by the natural sciences, in 1870 Pavlov entered St. Petersburg University in the natural department of the Faculty of Physics and Mathematics. His interest in physiology increased after he read I. Sechenov's book "Reflexes of the Brain", but he managed to master this subject only after he was trained in the laboratory of I. Zion, who studied the role of depressor nerves. Pavlov's first scientific study was the study of the secretory innervation of the pancreas. For her, Pavlov and M. Afanasiev were awarded the gold medal of the university. After receiving the title of candidate of natural sciences in 1875, Pavlov entered the third year of the Medical and Surgical Academy in St. Petersburg (later reorganized into the Military Medical Academy). Then Pavlov became an assistant at the Veterinary Institute, where he continued to study digestion and blood circulation for two years. In the summer of 1877 he worked in Breslau, Germany, with Rudolf Heidenhain, a specialist in digestion. The following year, Pavlov began working in the physiological laboratory at his Breslau clinic, not yet holding a medical degree, which Pavlov received in 1879. In the same year, Ivan Petrovich began research on the physiology of digestion, which continued for more than twenty years. Many of Pavlov's studies in the eighties concerned the circulatory system, in particular the regulation of heart function and blood pressure. In 1883, Pavlov defended his dissertation for the degree of Doctor of Medicine, devoted to the description of the nerves that control the functions of the heart. He was appointed Privatdozent to the Academy, but was forced to refuse this appointment due to additional work in Leipzig with Heidenhain and Karl Ludwig, two of the most eminent physiologists of the time. Two years later, Pavlov returned to Russia. By 1890, Pavlov's works were recognized by scientists around the world. From 1891, he headed the physiological department of the Institute of Experimental Medicine, organized with his active participation, while remaining the head of physiological research at the Military Medical Academy, where he worked from 1895 to 1925. In 1897, Pavlov brilliantly summarized his experimental material and theoretical principles in the classic work Lectures on the work of the main digestive glands (1897), which was very soon translated abroad. In his research, Pavlov used the methods of the mechanistic and holistic schools of biology and philosophy, which were considered incompatible. As a representative of mechanism, Pavlov believed that a complex system, such as the circulatory or digestive system, can be understood by examining each of their parts in turn; as a representative of the "philosophy of wholeness" he felt that these parts should be studied in an intact, living and healthy animal. For this reason, he opposed the traditional methods of vivisection, in which living laboratory animals were operated on without anesthesia to observe the functioning of their individual organs. Considering that an animal dying on the operating table and in pain cannot respond adequately to a healthy one, Pavlov acted on it surgically in such a way as to observe the activity of internal organs without disturbing their functions and the state of the animal. Pavlov's skill in this difficult surgery was unsurpassed. Moreover, he insisted on maintaining the same level of care, anesthesia and cleanliness as in human operations. Using these methods, Pavlov and his colleagues showed that each section of the digestive system - salivary and duodenal glands, stomach, pancreas and liver - adds certain substances to food in their various combinations, breaking it down into absorbable units of proteins, fats and carbohydrates. After isolating several digestive enzymes, Pavlov began to study their regulation and interaction. “The secretory nerves of the salivary glands were identified and studied quite thoroughly by Pavlov’s predecessors,” writes E.A. Asratyan, “by Claude Bernard, Heidenhain, Ludwig, Langley and others, but the conditions of acute vivisection experiments in which their studies were carried out did not allow them to reveal in its entirety the picture and regularities of the rich and versatile natural activity of these glands.Reflex secretion of saliva was a priori put in connection with the general excitability of receptors in the oral cavity, although it has long been known that these receptors are far from homogeneous in their structure and functions. In his systematic and careful chronic experiments, Pavlov established that the reflex secretion of saliva varies greatly in quantity and even in quality, depending on the nature, strength, quantity and duration of the action of natural stimuli in the form of food or rejected substances on the receptors of the oral cavity. Food or a rejected substance (acid, alkali, etc.) enters the mouth, what kind of food enters the mouth - meat, bread, milk or anything else, in what form (dry or liquid), in what quantity - from it depends on which salivary glands and at what pace they will work, what composition and how much saliva they will secrete, etc. For example, it has been shown that dry food causes more salivation than wet or liquid, acid causes saliva with a high content protein than food, river sand poured into the mouth also causes profuse salivation, and small stones placed in the mouth are pushed out of the mouth without causing saliva, etc. The variability in the quantity and quality of the secreted saliva also depends on its functional purpose - digestive, protective or sanitary-hygienic. For example, for edible substances, as a rule, thick saliva is secreted, and for rejected substances - liquid. At the same time, the share of participation of individual salivary glands, which produce predominantly liquid or predominantly thick saliva, changes accordingly. With the totality of these and other facts, Pavlov established a fact of fundamental importance: such a subtle and vivid variability of the reflex activity of the salivary glands is due to the specific excitability of different receptors in the oral cavity to each of these irritating agents, and these changes themselves are adaptive in nature. In 1904, Pavlov was awarded the Nobel Prize in Physiology or Medicine "for his work on the physiology of digestion, which has led to a clearer understanding of the vital aspects of this subject." In a speech at the award ceremony, K. A. G. Merner of the Karolinska Institute praised Pavlov's contributions to the physiology and chemistry of the digestive system. “Thanks to the work of Pavlov, we were able to advance in the study of this problem further than in all previous years,” Merner said. “Now we have a comprehensive understanding of the influence of one section of the digestive system on another, i. ready to work together." Throughout his scientific work, Pavlov retained an interest in the influence of the nervous system on the activity of internal organs. In the early twentieth century, his experiments on the digestive system led to the study of conditioned reflexes. In one of the experiments, called "imaginary feeding", Pavlov acted simply and in an original way. He made two "windows": one - in the wall of the stomach, the other - in the esophagus. Now the food that was fed to the operated and cured dog did not reach the stomach, fell out of the hole in the esophagus. But the stomach had time to receive a signal that food had entered the body, and began to prepare for work: to intensively secrete the juice necessary for digestion. It could be safely taken from the second hole and examined without interference. The dog could swallow the same portion of food for hours, which did not get further than the esophagus, and the experimenter worked at this time with abundantly flowing gastric juice. It was possible to vary the food and observe how the chemical composition of the gastric juice changes accordingly. But the main thing was different. For the first time, it was possible to experimentally prove that the work of the stomach depends on the nervous system and is controlled by it. Indeed, in the experiments of imaginary feeding, food did not enter directly into the stomach, but it began to work. Therefore, he received the command along the nerves coming from the mouth and esophagus. At the same time, it was worth cutting the nerves leading to the stomach - and the juice ceased to stand out. It was simply impossible to prove the regulatory role of the nervous system in digestion in other ways. Ivan Petrovich was the first to do this, leaving far behind his foreign colleagues and even R. Heidenhain himself, whose authority was recognized by everyone in Europe and to whom Pavlov had recently traveled to gain experience. "Any phenomenon in the external world can be turned into a temporary signal of an object that stimulates the salivary glands," Pavlov wrote, "if the stimulation of the mucous membrane of the oral cavity by this object is re-associated ... with the impact of a certain external phenomenon on other sensitive surfaces of the body." Of course, far from all the facts and theoretical positions of Pavlov on the physiology of the digestive system remain valid today. Numerous studies by scientists from various countries have made amendments and changes to some of them. However, in general, the modern physiology of digestion still retains the deep imprint of Pavlov's thought and work. His classic works still serve as the basis for more and more research. Author: Samin D.K.
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ Next Generation Solid State Drives from Toshiba ▪ Sensors implant people and create a single network
▪ section of the site Electrician's Handbook. Article selection ▪ article by George Sand (Amandine Aurora Lucile Dupin-Dudevant). Famous aphorisms ▪ article Where is the lake, which hides a whole park under water every year? Detailed answer ▪ article Sandarach glue. Simple recipes and tips
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
We recommend interesting articles Section 
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page