Morphological and Morphometric Study of the Digastric Muscle in Human Fetuses

Introduction: The digastric muscle, essential for functions such as speech and swallowing, has a dual embryological origin that contributes to its morphological variations. A thorough understanding of its characteristics during fetal development is crucial for anatomical and surgical practice. Objective: To investigate the morphological and morphometric characteristics of the digastric muscle in human fetuses, assessing the influence of gestational age, sex, and laterality. Materials and Methods: Twenty-six human fetuses (13 male and 13 female), fixed in formalin and without macroscopic abnormalities, were analyzed. They were obtained in compliance with Law 8,501 of 1992 at the Federal University of Sergipe. Gestational age was determined by an equation based on the heel-toe length measurement. Morphometric analyses included length and width measurements of the anterior belly, posterior belly, and intermediate tendon using a digital caliper. Morphological analysis classified digastric components according to De-Ary-Pires et al.’s typology. Results: Mean gestational age was 29.4 (±3.58) weeks. A significant positive correlation was observed between gestational age and the length and width of all digastric muscle components. Morphologically, the anterior belly was predominantly classified as Type I, while the intermediate tendon exhibited variations among Types I, II, and III. All posterior bellies were classified as Type I. No significant sex differences were found. Bilateral symmetry was predominant in most structures, except for the width of the anterior and middle points of the anterior belly. Conclusion: Gestational age is the main determinant of morphological and morphometric development of the digastric muscle during the fetal period. Sex and laterality had no significant influence. Further studies are suggested to compare fetal and adult development to elucidate the clinical implications of anatomical variations.