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FORMATION OF THE BLOOD SUPPLY OF THE
DIFFERENT DEPARTMENTS OF THE ESOPHAGUS OF
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aorta and spinal column. In germs of 4.5-6.0 mm TCL, the rudiment of the oesophagus may look like a 520-540 µm tube. The tracheo-pulmonary rudiment is located ventrally, dorsally - the rudiment of the vertebral column. The wall of the oesophagus is represented by a single-spherical cylindrical epithelium placed on the basement membrane. The height of the epithelium becomes 10-12 µm. Cell nuclei are oval in shape, located at different levels: some nuclei are located apically, some of the nuclei are closer to the base, and most are in the middle part of the cells. Outside of the basement membrane, a layer of undifferentiated mesenchyme of varying thickness is found. The lumen of the esophagus is 7-8 µm. In 5-week-old embryos, due to the active proliferation of the epithelium of the esophageal mucosa, the so-called physiological atresia of the organ occurs. The main feature in the structure of physiological atresia in embryogenesis is the formation of vacuoles (the first stage). At the first stage, active proliferation of the epithelium occurs in the organs of the digestive system, the mucous membrane thickens, the lumen of the organ narrows, in some places, until it is completely closed. The first row of cells of the cylindrical epithelium lies on the basement membrane, and the nuclei of other rows (there may be 2-3 rows) are located closer to the lumen. Most of the nuclei are located in the middle section of the cells.
The lumen of the rudiment of the esophagus in transverse sections has an oval shape and is 8-10 µm. Its lumen at the level of the bifurcation of the trachea, due to the intensive development of the epithelium, is almost absent, which should be considered as a stage in the formation of an epithelial "plug", the height of which reaches 120-126 µm. Cranial and caudal to the epithelial "plug", the lumen of the esophageal rudiment 10-12 µm wide, is lined with a two-layer cylindrical epithelium, the nuclei of which are located at different levels. The cells that form the epithelial "plug" are smaller than the cells of the two-layered cylindrical epithelium, as a result of which the epithelial
"plug" has the appearance of a formation consisting of nuclei with a small amount of cytoplasm. The source of origin of the epithelium of the mucous membrane and glands of the esophagus is the endoderm, the muscular membrane of the upper part of the esophagus is formed from the mesoderm of 4-6 gill arches, the lower part - from the mesenchyme of the somites surrounding the foregut below the 6th branchial intestine.
The rudiment of the circular layer of the muscular membrane is detected in embryos of 9.0-9.5 mm PCL, and the longitudinal layer - in pre-fruits 18.0-19.0 mm PCL. In prefetuses 60.0-75.0 mm PCL, an active process of transformation of the epithelium of the esophageal mucosa occurs. In embryos 4.5-5 weeks old (embryos 6.0-7.5 mm PCL), the primary laying of blood vessels in the esophageal mesenchyme layer looks like separate islands of hematopoiesis. By the end of the 6th week (embryos 10.0-12.0 mm PCL) in the same layer of the wall, an almost continuous dense chain of these islands is determined, some of which are separated from the surrounding mesenchymal cells, located in one row. In the outer part of the esophageal mesenchyme layer, large vessels with a distinct wall are determined. In fetuses of 6th weeks, the separation of blood cells by mesenchymal cells becomes more pronounced, so that a continuous network of thin vessels such as capillaries anastomosing among themselves is determined. On the 7-8th week of development of the vessel, suitable from the outside to the esophagus, a number of branches are sent that penetrate into the thickness
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of the wall and anastomose with a network of vessels formed from foci of local hematopoiesis. In the first three weeks of intrauterine development, the final intestine connects to the canal of the primary kidney, opening into one common cavity - the cloaca. At the end of the 7th week, the development of the cloaca is divided by a septum from the mesoblast into the anterior and posterior sections, thereby forming two end tubes. The anterior septum passes into the allantois, from which the ureters and bladder are subsequently formed, and the rectum and anus are formed from the posterior tube.
The source of blood supply to the cervical esophagus in fetuses is the branches of the right and left lower thyroid arteries. On some preparations, we observed 2 thin branches extending from the left inferior thyroid artery and one from the right inferior thyroid artery, arterial branches of insignificant diameter extend from the ventral arteries of the bodies of the lower cervical vertebrae. In most of the studied fetuses (16 fetuses), the sources of blood supply to the esophagus are bronchial arteries. It should be noted that there are several bronchial arteries, but branches to the esophagus depart from each.
More often, the arterial branch to the esophagus departs from the right bronchial artery.
All the studied fetuses had 1 to 3 arterial branches to the esophagus extending from the thoracic descending aorta. In 9 fetuses, 2 branches were observed more often, extending from the thoracic aorta at the level of 7-8 thoracic vertebrae. The constant source of blood supply to the middle third of the thoracic esophagus is the branch of the descending thoracic aorta and the right bronchial artery, and the left posterior intercostal arteries are non-permanent. The constant source of blood supply to the lower third of the thoracic esophagus is the branch of the descending thoracic aorta, and the bronchial arteries are non-permanent. The constant source of blood supply to the abdominal part of the esophagus is the left gastric artery, the non-permanent source is the lower left phrenic artery, the splenic artery. In one case, an arterial branch from the abdominal trunk departed to the abdominal part of the esophagus. It should be noted that the discharge of arterial branches to the esophagus from the sources of its blood supply occurs at different angles: close to straight, sharp, less often blunt. It is indisputable that different angles are not functionally equivalent. The identified features of the origin and branching of the arterial branches of the esophagus, from our point of view, are closely related to the growth of the organ in length in the prenatal period of human ontogenesis. The blood supply of the cervical esophagus is carried out by the arterial branches of the thyro-cervical, costal-cervical trunks, spinal arteries and intrathoracic artery. The blood supply to the thoracic esophagus is carried out by the arterial branches of the descending thoracic aorta, mainly by the right bronchial artery and the left posterior intercostal arteries. The blood supply to the abdominal esophagus is carried out by the left gastric artery, the left inferior phrenic artery, and sometimes by the arterial branch of the abdominal trunk and splenic artery. In the cervical esophagus and in the upper part of the thoracic region, the arterial branches approach the esophagus, as a rule, on the sides, and in the middle and lower parts - in front, and the arterial branches approach the abdominal region from all sides. The greatest number of arterial branches approaches the upper part of the thoracic and abdominal sections of the esophagus. The study of the morphology of extraorganic arteries, their branching in the thickness of the wall of the esophagus in fetuses showed that the
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esophagus has two main arterial plexuses - muscular and submucosal. Branches depart from these arterial plexuses to the muscular layer and mucosa of the esophagus, the location of the intraorgan arterial branches is not the same - from circular to longitudinal.
Conclusion:
Blood supply: the cervical part of the esophagus is supplied by arterial branches of the thyroid-cervical, costo-cervical trunks, vertebral arteries and the intrathoracic artery; the thoracic part of the esophagus is supplied by arterial branches of the descending thoracic aorta, mainly the right bronchial artery and the left posterior intercostal arteries; of the abdominal part of the esophagus is carried out by the left gastric artery, the left lower diaphragmatic artery, sometimes the arterial branch of the abdominal trunk and the splenic artery.
Referens:
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Transcriptome Dynamics in the Developing Larynx, Trachea, and Esophagus.
Thibeault Front Cell Dev Biol. 2022;10:942622.
doi: 10.3389/fcell.2022.942622
2. Zhang Y, Jiang M, Kim E, et al. Development and Stem Cells of the Esophagus Semin Cell Dev Biol. 2017; 66: 25-35.
doi: 10.1016/j.semcdb.2016.12.008
3. Billmyre KK, Hutson M, Klingensmith J. One Shall Become Two: Separation of the Esophagus and Trachea from the Common Foregut Tube. Dev. Dyn. 2015;244 (3):277-88. doi: 10.1002/dvdy.24219
4. Marchuk FD, Tomyuk II. Before nutrition, the development of wall balls and the blood stream of the esophagus in the prenatal period, the ontogenesis of humans. Ukr.
мedical аlmanac. 2000;3(1):40.
5. Que JM. The initial establishment and epithelial morphogenesis of the esophagus: a new model of tracheal-esophageal separation and transition of simple columnar into stratified squamous epithelium in the developing esophagus. Wiley Interdiscip Rev Dev Biol. 2015;4(4):419-30.
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