Peculiarities of development of the suprahyoid muscles of the neck at an early period of human ontogenesis

Abstract

Objective – of the work is to clarify the sources of germs and find out the chronological sequence of morphogenesis of the muscular structures of the suprahyoid triangles of the anterior cervical region in the embryonic and prefetal periods of human ontogenesis.Material and methods. 25 series of consecutive histological sections of human embryos and prefetuses aged from 5 till 12 weeks of development (6.0-80.0 mm parietal-coccygeal length (PCL)) using a complex methods of morphological examination (anthropometry, morphometry, microscopy, three-dimensional computer reconstruction and statistical analysis) were studied.Results. The rudiment of digastric muscle was first detected in 7-week-old prefetuses (15.5-16.0 mm PCL). The medial surface of Meckel’s cartilage is the site of attachment of the superior belly of the digastric muscle. At the 12th week of intrauterine development, the digastric muscle finally acquires its definitive attachment to the internal surface of the body of mandible. The rudiment of the mylohyoid muscle was first detected in 6-week-old embryos (10.0-12.0 mm PCL). The place of its attachment begins near the mental symphysis, the attachment of the muscle to the anlage of the hyoid bone was detected only at the end of the 7th week of intrauterine development (prefetuses 19.0-20.0 mm PCL). The anlage of the geniohyoid muscle was first determined in the 6-week-old human embryos. In prefetuses of 15.5- 40.0 mm PCL, geniohyoid muscle begins on the medial surface of Meckel’s cartilage, and from the 12th week of intrauterine development (prefetuses 75.0-77.0 mm PCL), the muscle attachment is localized on the internal surface of the body of mandible. The genioglossus muscle is found on the internal and caudal surfaces of Mekel’s cartilage, but from the middle of the 12th week of intrauterine development the site of its attachment moves to the medial-caudal surface of the body of mandible.Conclusions. 1. The anlages of all muscles that delimit the boundaries of the suprahyoid triangles of the neck were identified at the beginning of the 7 th week of intrauterine development (prefetuses 15.5-16.0 mm PCL). 2. The suprahyoid muscles attach to the medial surface of Meckel’s cartilage, but during the 8-11th weeks of intrauterine development, the attachment sites gradually move to the bony edges of the mandible, which cover Meckel’s cartilage. 3. In the prenatal period of development, bundles of the mylohyoid muscle leave the anterior region of the mental symphysis free. 4. In human prefetuses, only the geniohyoid and mylohyoid muscles were attached to the hyoid bone.