EMBRYOTOPOGRAPHIC FEATURES OF THE ILEOCECAL SEGMENT

This is what ensured the formation of the definitive state of the intestines, which guarantees gradual, portioned, cyclical, unilateral, phased entry of the food lump into the corresponding intestinal segments. One of the key locking mechanisms, and at the same time a massive reflexogenic field, which provides the specified properties of the intestine is the ileocecal sphincter- valve apparatus represented by the Bauhinia valve and the iliac papilla. This locking apparatus is closely morphofunctionally connected with adjacent structures, parts of which it is: the cecum, the ascending colon, the terminal segment of the ileum, the appendix. Purpose – to study the spatiotemporal embryotopographic features of the formation of the ileocecal segment of a person. Material and methods. The study was conducted on 20 specimens of human embryos using of methods of histological and morphological research (morphometry, microscopy) and statistical analysis. Results. The article describes the laying of the ileocecal segment of the intestine, which is formed at the end of the embryonic period in two stages: first, at the 5th week of prenatal development, the rudiment of the terminal ileum and the initial part of the colon appears, and then, at the 6th week, the rudiment of the cecum. It has been established that in embryos of 4.5 mm PCL the primary intestine has a thickness of 96.0±6.0 μm, located slightly ventral to the chord between the gastric fold and the cloaca. In 5-week-old embryos (5.5-8.0 mm PCL) significant changes in the topography of the primary intestine occur – it lengthens and bulges in the sagittal plane, which leads to the appearance of a U-shaped loop that protrudes into the abdominal stalk, forming a «physiological umbilical hernia». In embryos of the 6th week of the development (8.5-13.0 mm PCL) further changes in the topographic and anatomical relationships of the intestinal fold are observed. The cranial knee of the intestinal loop increases in length and forms 2-3 loops, some of which are located in the «physiological umbilical hernia», and the other in the abdominal cavity. At the beginning of the pre-fetal period (7th week of development, specimens 14.0-20.0 mm PCL) the total length of the expanded section of the intestine reaches 4800±40 μm, the width at the site of the lateral protrusion is 1800±30 μm. Between the junction of the small and large intestines, the lateral protrusion has a coneshaped shape with an expansion at the apex. Conclusions. The ileocecal segment of the intestine is laid at the end of the embryonic period in two stages: first, at the 5th week of prenatal development, the rudiment of the terminal ileum and the initial part of the colon appears, and then, at the 6th week, the rudiment of the cecum. The separation of the rudiment of the vermiform appendix from the cecum begins at the 7th week.