Ramón Norambuena-González & Julio Cárdenas Valenzuela

The circular arrangement for the inner layer and the longitudinal arrangement for the outer layer was the traditionally accepted model by the scientific community in terms of the orientation of the muscular layers of the small intestine’s muscular coat. However, in the middle of the 17th century, that model began to be questioned and a new spiral model for the orientation of the muscular layers was introduced, which was believed by various researchers throughout history. Due to this controversy, the International Anatomical Terminology still maintains both terms, contrary to its principles of maintaining a single term. In order to find a solution to this historical controversy, a bibliographic research on different works on the orientation of the muscular layers of the muscular coat was carried out. Moreover, a review of anatomy and histology papers in the library of the Institute of Anatomy of the department of Medicine at Universidad de Chile and papers used in current curriculum of scientific degrees. Some researchers have described a circular model for the internal layer and a longitudinal model for the external layer, others a spiral model. However, the main anatomy and histology texts still maintain the traditional description. As a result, the aim of this study was to solve this contradiction.

KEY WORDS: Anatomical terminology; Muscular layer; Internal circular; External longitudinal; Spiral model.

NORAMBUENA-GONZÁLEZ, R. & CÁRDENAS VALENZUELA, J. Muscular layer of the small intestine. Can two models coexist? A critique of the anatomical literature. Int. J. Morphol., 43(5):1658-1661, 2025.