Derivation of the anterior belly of the digastric muscle receiving twigs from the mylohyoid and facial nerves.
The anterior belly of the digastric muscle is usually supplied by the mylohyoid nerve, and in general anatomy textbooks, the anterior belly is invariably described as receiving no other nerve except the mylohyoid nerve. In fact, however, it is sometimes supplied by a branch of the facial nerve in addition to the mylohyoid nerve. Such cases were found in 8 bodies or 9 head sides among 539 bodies or 1078 head sides of Japanese subjects. Those nine cases were investigated in detail and it was clarified that they had the following three characteristics in common: (1) the twig originating from the facial nerve appears as the twig of the stylohyoid branch in most cases, (2) the twig from the facial nerve enters the anterior belly on its lower (shallow) surface and the twig of the mylohyoid nerve on its upper (deep) surface, (3) the twig of the mylohyoid nerve is distributed to the deep region and the twig of the stylohyoid branch is distributed to the shallow region of the anterior belly. From these results, it was concluded that the anterior belly, receiving the twigs of the mylohyoid and facial nerves, had been formed by secondarily combining the most ventral and rostral part of the primordium of the stylohyoid muscle in the second branchial arch with the caudal part of the primordium of the anterior belly in the first branchial arch.
Kawai
Katsushi
K
Department of Anatomy, Kumamoto University School of Medicine, 2-2-1 Honjo, Kumamoto, 860-0811, Japan.
Koizumi
Masahiro
M
Honma
Satoru
S
Tokiyoshi
Akinari
A
Kodama
Kodo
K
D001344:Autopsy; D005152:Facial Muscles / Q000294:innervation*; D005154:Facial Nerve / Q000033:anatomy & histology*; D007839:Functional Laterality; D006801:Humans; D007564:Japan