THE CLOACA EPITHELIAL LAYER HETEROMORPHY IN THE GRASS FROG RANA TEMPORARIA

In amphibians, the cloaca is formed during embryogenesis and functions throughout life. The cloaca as a temporary (provisional) formation also exists in early human embryogenesis, and its developmental disturbances lead to a number of congenital pathologies, one of which is persistent cloaca. Understanding the histogenetic causes of congenital anomalies can be achieved by taking into account phylogenetic studies. The starting point for them can be the identification of histogenetic features of the formation of the cloaca, its epithelial layer and derivatives using amphibians (Grass frog, Rana temporaria), birds, mammals and humans as an example. The purpose of the study is to characterize the epithelial layer of the cloaca in amphibians. The object of the study was the caudal section of the gastrointestinal tract of adult individuals of the species Rana temporaria, n=10. Morphometric analysis of epithelial cells of three parts of the cloaca - cutaneous, urinary and intestinal - was performed on paraffin sections stained with hematoxylin and eosin. The following karyometric parameters were measured: long and short axes of the nucleus, nuclear area, and nuclear elongation. As a result of morphometric analysis, it was established that the length of the frog cloaca parts varies. In the cutaneous part it is 893±82,2 μm, in the urinary part - 320±29,2 μm, in the intestinal part - 1092±110 μm. The epithelial layer of each of the three parts of the cloaca is characterized by cell heteromorphism. The skin part is represented by a multilayered mucous epithelium, which breaks off along the line of contact with the epithelium of the urinary part and then the layer continues with an epithelium of a different structure and morphometric parameters. In the area of ​​contact with the intestinal epithelium, a clear demarcation line is also observed. The epithelial layer of each of the three parts of the cloaca is characterized not only by differences in morphology, but also by differences in the karyometric indices of the cells, which indicates different embryonic sources of development. Morphometric analysis of the cellular composition of the epithelial layer of different parts of the frog cloaca allows for differential diagnostics of different parts of the anorectal tract in the embryogenesis of higher vertebrates.

1. Zavarzin AA. Kratkoe rukovodstvo po embriologii cheloveka i pozvonochnykh zhivotnykh. L.: Medgiz, 1938.- 215s. In Russian

2. Khlopin NG. Obshchebiologicheskie i eksperimental'nye osnovy gistologii. L.: izdat. Akademii nauk SSSR, 1946.- 491s. In Russian

3. Knorre AG. Embrional'ny gistogenez (Morfologicheskie ocherki). L.: Meditsina, 1971.- 431s. In Russian.

4. Borisov IN, Dunaev PV, Bazhanov AN. Filogeneticheskie osnovy tkanevoy organizatsii zhivotnykh. Novosibirsk: Nauka, 1986.- 236s. In Russian

5. Reva IV, Yamamoto T, Odintsova IA i dr. Prenatal'ny gistogenez struktur zheludochno-kishechnogo trakta cheloveka. Vladivostok: Izdatel'stvo DVFU, 2024.- 134s. In Russian

6. Warne SA, Hiorns MP, Curry J, Mushtaq I. Understanding cloacal anomalies. Arch Dis Child. 2011;96(11):1072–1076. https://doi.org/10.1136/adc.2009.175034

7. Miyake Y, Lane GJ, Yamataka A. Embryology and anatomy of anorectal malformations. Semin Pediatr Surg. 2022;31(6):151226. https://doi.org/10.1016/j.sempedsurg.2022.151226

8. Danilov RK, Zheglova MJu, Komarova AS, Odintsova IA. Innovatsionny podkhod k izucheniyu tkanevykh proizvodnykh kloaki pozvo-nochnykh. V kn.: Innovatsionnye tekhnologii izucheniya gistogeneza, reaktivnosti i regeneratsii tkaney. Trudy Voenno-meditsinskoy akad-emii. T. 263 / Pod red. R.G. Makieva, I.A. Odintsovoy. SPb.: VMedA, 2024.- S. 64–70. In Russian

9. Solov'yov GS, Panteleev SM, Shidin VA, Yanin VL. Divergentsiya organogenezov i divergentny mekhanizm evolyutsionirovaniya or-ganov. Morfologiya. 2019;155(2):266. In Russian

10. Solov''yov GS, Yanin VL, Panteleev SM i dr. Problemy morfogeneza, prezumptsiya provizornosti. V kn.: Voprosy morfologii XXI veka. Vyp. 6. SPb.: Izdatel'stvo DEAN, 2021.- S. 62–74. In Russian

11. Aptekar' IA, Akhmatov AV, Vikhareva LV i dr. O «rezervnykh» istochnikakh i mekhanizmakh morfogeneza. V kn.: Voprosy morfologii XXI veka. Vyp.8. SPb.: Izdatel'stvo DEAN, 2024.- S. 29–38. In Russian

12. Khesin YaE. Razmery yader i funktsional'noe sostoyanie kletok. M.: Meditsina, 1967.- 423s. In Russian

13. Komarova AS. Osobennosti stroeniya epitelial'noy vystilki kloaki u polovozrelykh beskhvostykh zemnovodnykh vida Rana temporaria. V kn.: Innovatsionnye tekhnologii izucheniya gistogeneza, reaktivnosti i regeneratsii tkaney. Trudy Voenno-meditsinskoj akademii. SPb.: VMedA, 2024.- S. 126–130. In Russian

14. Danilov RK, Borovaya ND, Klochkov TG. Eksperimental'no-gistologichesky analiz gistogeneza i regeneratsii tkaney. Nekotorye itogi XX veka i perspektivy dal'neyshikh issledovany. Morfologiya. 2000;1:7‒16. In Russian

15. Kruepunga N, Hikspoors JPJM, Mekonen HK et al. The development of the cloaca in the human embryo. J Anat. 2018;233(6):724–739. https://doi.org/10.1111/joa.12882

16. Thomas DFM. The embryology of persistent cloaca and urogenital sinus malformations. Asian J Androl. 2020;22(2):124‒128. https://doi.org/10.4103/aja.aja_72_19

17. Singh S, Kayastha A, Thapa A et al. Omphalocele, exstrophy of sloaca, imperforate anus, and spinal defects complex: a case report. JNMA J Nepal Med Assoc. 2023;61(260):375–378. https://doi.org/10.31729/jnma.8048

18. Vacaru A, Won MM, Raymond SL et al. Cloacal dysgenesis sequence in a preterm neonate. Am J Case Rep. 2024;25:e942203. https://doi.org/10.12659/AJCR.942203

19. Qi BQ, Beasley SW, Williams AK, Fizelle F. Apoptosis during regression of the tailgut and septation of the cloaca. J Pediatr Surg Int. 2000;35(11):1556–1561. https://doi.org/10.1053/jpsu.2000.18309

20. Ding Y, Wang Y, Lyu Y et al. Urogenital sinus malformation: from development to management. Chen. Intractable Rare Dis Res. 2023;12(2):78–87. https://doi.org/10.5582/irdr.2023.01027