Anatomical variation of the anterior belly of the digastric muscle: case report and clinical implications

The digastric muscle is a suprahyoid muscle composed of two bellies connected by an intermediate tendon.This muscle participates in deglutition and mandibular movements. The anterior belly of the digastric muscleis localized superficially to the mylohyoid and deeply to the platysma muscle. During dissection of this regionof an embedded cadaver, an accessory anterior belly of digastric muscle was observed bilaterally. The accessorybellies were similar but not symmetrical. They were composed of two segments, one long and one short, onboth sides, and when observed together these appeared to form the letter “X”. The accessory fibers, on bothsides, originated from the anterior digastric muscle and inserted medially to the digastric fossa. Anatomicvariations of the digastric muscle may influence mastication and deglutition. Moreover, the accessory digastricmuscle affects diagnostic imaging and therapeutic procedures in head and neck surgery and must be consideredin procedures involving this area.

Comportamento dos nervos glossofaríngeo e vago, na região retrofaríngea de ovinos: origem aparente no crânio, trajeto, ramificação e distribuição / Behavior of the glossopharyngeal and vagus nerves in the retropharyngeal region of sheep: apparent origin in cranium, course, branching and distribution

In 60 hemiheads of sheep of the Santa Ines breed the apparent origin in the skull of itinerary, ramification and distribution of the glossopharingeal nerve (Gf) and the vagus nerve (Vg) in the retropharyngeal region (Rr) were studied. By fixation and dissection of the specimens it was seen that the glossopharyngeal nerve and the vagus nerve arise from the jugular foramen in 100 percent of the cases. The right and the left glossopharingeal nerve (Glde) are frequently (86.6 percent) located more medially to the tympanic bulla, pass caudally to the stylohyoid bone, bypass the margin of the caudal stylopharyngeal muscle, the tonsilla, of the pharyngeal and the lingual mucous membrane. These branches are distributed, respectively, in the carotid sinus, pharyngeal musculature, soft palate, stylopharyngeal muscle, palatine tonsil, pharyngeal mucosa and the caudal third of the tongue (100 percent). The right and the left vagus nerve run caudally in association with the accessory nerves (Ac) up to the atlas (70 percent) and go then medially to the occipital artery, dorsally to the common carotid and the sympathetic trunk in the cervical region (80 percent). The vague nerves have pharyngeal (86.6 percent) and cranial laryngeal (100 percent) branches.

Em 60 hemicabeças de ovinos da raça Santa Inês foram estudadas a origem aparente no crânio, trajeto, ramificação e distribuição do nervo glossofaríngeo (Gf) e do nervo vago (Vg), na região retrofaríngea (Rr). Mediante fixação e dissecação das peças, foi observado que os nervos glossofaríngeos e vagos originam-se no forame jugular em 100 por cento dos casos. Os nervos glossofaríngeos direito e esquerdo (Gfde) são localizados, com maior freqüência (86,6 por cento), medialmente à bula timpânica, passam caudalmente ao osso estiloióide, contornam a margem caudal do músculo estilofaríngeo caudal, tonsilar, da mucosa faríngea e lingual. Estes ramos distribuemse, respectivamente, no seio carotídeo, musculatura faríngea, palato mole, músculo estilofaríngeo caudal, tonsila palatina, mucosa faríngea e terço caudal da língua (100 por cento). Os nervos vagos direito e esquerdo (Vgde) correm caudalmente em associação com os nervos acessórios (Ac) até o atlas (70 por cento), após o que passam medialmente à artéria occipital, dorsalmente à carótida comum e ao tronco simpático, na região cervical (80 por cento). Os ramos dos nervos vagos são os faríngeos (86,66 por cento) e os laríngeos craniais (100 por cento).