Development of neuromuscular spindles in the muscles of the floor of the human oral cavity during intrauterine development
Mitchenok, V.I.
Arkhiv Anatomii Gistologii i Embriologii 76(4): 13-20
1979
ISSN/ISBN: 0004-1947 PMID: 156015 Document Number: 153679
By means of histological, neurohistological, histochemical and morphometrical techniques the development, number and histotopography of neuromuscular spindles have been studied in 860 muscles of the mouth cavity fundus obtained from 108 human embryos, fetuses and newborns. In genioglossal and in geniohyoid muscles, the spindles are layed down at the 7th week of gestation. Their differentiation starts at the 9th week -- with forming the first sensitive endings, nuclear bursa and cellular elements of the spindle capsule. By the 14th week, the subcapsular space becomes evident, and by the 20th week of embryogenesis neuromuscular spindles resemble definitive structures. In the anterior belly of the digastric muscle, the foundation and initial differentiation of the spindles is retarded. The mylohyoid muscle has no spindles. Morphogenesis of neuromuscular spindles has been studied with special reference to the beginning of functional activity of the fundal muscles in the mouth cavity during embryogenesis in view of the theory of systemogenesis.