• Interactions of Organs with Uneven Growth and Volume in the Base of Organogenesis

    Petrenko Valeriy Mikhaylovich*

     

    1MD, PhD, DSc, Professor, Senior Research Associate, Rehabilitation of Immobile Patients, St. Petersburg, 194021, Russian Federation

    *Correspondence to: Petrenko Valeriy Mikhaylovich

    Citation: Petrenko VM (2019) Interactions of Organs with Uneven Growth and Volume in the Base of Organogenesis. SCIOL Biomed 2019;3:152-154

  • Abstract

     

    Mechanics of organogenesis in ontogeny of different animals sold through interorgan interaction. They determine the formation of definitive anatomical topographical relationships of organs in embryogenesis on the basis of uneven growth of organs, including the walls of body cavities (limiting capacity factor). The ratio of growth rates of organs in different directions and their volumes predetermines the influence of this body on the development of neighboring organs. The key role in the organogenesis of the abdominal cavity of the embryo is played by its main organ of hematopoiesis - nutrition) - the liver (placental mammals) or the yolk sac (birds, reptiles). From the size, timing and rate of change in such an organ depends on the entire organogenesis in the abdominal cavity of the embryo, including the formation and subsequent reduction of physiological umbilical hernia.

     

    Keywords


    Organ, Uneven growth, Volume, Interaction, Mechanics, Organogenesis

    Introduction


    The driving force behind the development of organisms is the interaction of different systems [1], including organs. Its mechanisms in evolution and ontogenesis are described in the literature [2-4]. The now famous law Minot concerning the uneven growth as the main mode of development was proclaimed more than a century ago. Thompson later stated that the morphogenesis of the body and organs is determined by the speed of their growth in different directions. Svetlov introduced the term «differentiating growth»: a significant part of the differentiation is carried out by uneven growth. Development occurs under certain conditions, which can cause uneven growth (or in a more general form - movement) of the developing system. In recent years, experiments with different factors affecting the individual and his organs to study the mechanics of development have become widespread, and increasingly such experiments are conducted on lower animals and to study the segmentation of their bodies [5-7]. For knowledge of mechanisms of organogenesis, it is necessary to use constant "experiments" of the nature [8] - a method of comparison of bodies at animals of different types and classes. But the organ should be studied as a part of the whole organism in inseparable connection with its function [9].

    About Mechanics of Organogenesis


    My comparative studies [10] have shown, that the liver of placental mammals is the largest organ of their embryos, as it serves as the center of hematopoiesis. The yolk sac in these animals is usually small and early reduced. In birds and even more reptiles, the yolk sac, a very important organ of the embryo's nutrition, is reduced much later, which delays the reduction of physiological umbilical hernia into the abdominal cavity of the embryo. This can be attributed to the absence of birds and reptiles secondary adhesions of the peritoneum. In rats, there are no dorsal secondary peritoneal splices, which correlates with a slow decrease in the size of the liver relative to the capacity of the abdominal cavity in the fetus (compared to humans). Especially strongly this process is influenced by the growth of the dorsal, retroportal areas in the liver of an embryo rat - until the "doubling" her liver. They move the stomach and duodenum away from the dorsal abdominal wall while maintaining the mobility of the root of the dorsal mesentery. The rotation of the primary intestinal loop in rat embryogenesis is slowed down with the reduction and loss of a number of stages. The pig's liver grows approximately as in man. But the pig embryo large, slowly degenerating mesonephros inhibit cranial growth ("ascent" into the abdominal cavity) pelvic renal and postrenal part of the posterior Vena cava, contribute to the formation of larger cranial and (especially) the caudal intersubcardinal venous anastomoses. In the chicken embryo, the liver is relatively small (because its yolk nutrition prevails), but the mesonephros degenerate slowly, and the kidneys retain their pelvic position. Therefore, the postrenal part of the posterior Vena cava of the domestic chicken is not formed at all.

    In human fetuses and placental mammals organogenesis in the abdominal cavity is determined primarily by the ratio of volumes and features of the growth of the liver and intestines. This thesis is well illustrated by the inverse ratio of the liver and cecum in rodents: Omnivorous and mobile rat - large liver, small colon in general and the cecum in its composition; sedentary herbivorous guinea pig - liver smaller, huge cecum and permanent loop ascending colon; a very mobile herbivorous degu with a small liver, similar in relative volume in humans, occupies an intermediate position in this series in the cecum, but is clearly closer to the guinea pig. The change in the relative growth (volume) of the right and left lobes of the liver in different subspecies of the latter directly correlates with the position and structure of the duodenum and ascending colon.

    Interorgan interactions in embryogenesis determine the formation of definitive anatomical and topographic relationships of organs on the basis of uneven growth of organs, including the walls of body cavities (limiting capacity factor). The ratio of the growth rate of organs in different directions changes with the change in the influence of this body on the development of neighboring organs. The organs are made up of tissue. Inter-tissue interactions such as stromal epithelio (mesenchymal epithelio) are the basis of organogenesis. Its main mechanism of multifocal growth of the embryo: proliferating epithelial rudiments of organs alternate with intermediate areas of the mesenchyme, which taper between the sections of bodies in general. Thus, the individual spatial organization is carried out in the process of inter-organ interactions, on the basis of uneven growth of organs, the rate of which usually decreases with the maturation of their constituent tissues.

    To understand the molecular mechanisms underlying the development of the intestine, morphogenesis of loops of the small intestine, special studies are conducted. Their results showed that biochemical signals act on tissue-level mechanics to control organogenesis and suggest a possible mechanism by which they can be modulated to achieve different morphologies through evolution [11].

    Physiological Umbilical Hernia and its Morphogenetic Value

    The human small intestine forms 12-16 loops, including 7 permanent distal loops of the ileum. So far, this fact has not been explained. I [12,13] studied 200 human embryos 4-20 weeks, including the method of preparation, starting with the embryo 5.5 weeks. In embryo 4 weeks rapidly extending the middle intestine forms a ventral bend in the sagittal plane - the primary intestinal loop [14], which extends beyond the celomic cavity under liver pressure for 5 weeks. When the tip of this loop enters the cavity of the umbilical stalk, the umbilical intestinal loop is formed. Embryos 6, 5-7 weeks begins spiralization of the descending limb of the umbilical intestinal loop with the formation of the first secondary intestinal loops. Extending in a limited volume of the cavity of the umbilical stalk, the middle intestine "develops" into three triangular loops on the right and below the cecum. Expanding, they become horseshoe-shaped. In embryos 7-8 weeks are determined first 5, and then all 7 loops of the ileum. They are entirely in the cavity of the umbilical hernial sac at different stages of morphogenesis and in different planes. They are entirely in the cavity of the umbilical hernial sac at different stages of morphogenesis and in different planes. On the 8th week, the liver begins to decrease in size relative to the abdominal cavity. And only at this stage of development there are the first three triangular folds of the intraabdominal segment of the descending knee of the primary intestinal loop, which belong to the jejunum. Further relative reduction of the liver, as well as the reduction of mesonephros and shortening of the root of the mesentery of the primary intestinal loop lead to the repositioning of the umbilical intestinal loop into the abdominal cavity of the fetus. The process is usually completed in the middle of the 10th week, when under the lower edge of the liver, transverse colon and caecum, two tangles of loops of the small intestine are determined: Ventral - 7 loops of the ileum, dorsal - 5-9 loops of the jejunum. Soon they merge into a single array. Thus, the loops of the ileum appear earlier than the loops of the jejunum. At the heart of their morphogenesis is the intensive growth of the middle intestine in length in a very dense environment, especially - the liver. The cavity of the umbilical stalk is more "spacious" and stable in volume than the abdominal cavity. This can explain the earlier formation of 7 ileum loops. The loops of the jejunum occur later, when inhibiting the variable growth of the liver, and are formed in a very variable capacity of the abdominal cavity, surrounded by organs with individually very variable growth.

    Conclusion

    Mechanics of organogenesis in ontogeny of different animals sold through interorgan interaction. They determine the formation of definitive anatomical topographical relationships of organs in embryogenesis on the basis of uneven growth of organs, including the walls of body cavities (limiting capacity factor). The ratio of growth rates of organs in different directions and their volumes predetermines the influence of this body on the development of neighboring organs. The key role in the organogenesis of the abdominal cavity of the embryo is played by its main organ of hematopoiesis - nutrition) - the liver (placental mammals) or the yolk sac (birds, reptiles). From the size, timing and rate of change in such an organ depends on the entire organogenesis in the abdominal cavity of the embryo, including the formation and subsequent reduction of physiological umbilical hernia.

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