| Mandibular symphysis | |
|---|---|
.png) Anterior view of mandible, showing mandibular symphysis (red broken line) | |
 Medial surface of the left half of the mandible, dis-articulated from the right side at the mandibular symphysis | |
| Details | |
| Identifiers | |
| Latin | symphysis mandibulae |
| TA98 | A02.1.15.004 |
| TA2 | 838 |
| FMA | 75779 |
| Anatomical terms of bone | |
In human anatomy, thefacial skeleton of theskull the external surface of themandible is marked in the median line by a faint ridge, indicating themandibular symphysis (Latin:symphysis menti) or line of junction where the two lateral halves of the mandible typically fuse in the first year of life (6–9 months after birth).[1] It is not a truesymphysis as there is no cartilage between the two sides of the mandible.
This ridge divides below and encloses a triangular eminence, themental protuberance, the base of which is depressed in the center but raised on either side to form themental tubercle. The lowest (most inferior) point of the mandibular symphysis—commonly referred to as the chin—is called thementon.[2][3]
It serves as the origin for thegeniohyoid and thegenioglossus muscles.
Solitary mammalian carnivores that rely on a powerful canine bite to subdue their prey have a strong mandibular symphysis, while pack hunters delivering shallow bites have a weaker one.[4] When filter feeding, thebaleen whales, of the suborder Mysticeti, can dynamically expand their oral cavity in order to accommodate enormous volumes of sea water. This is made possible thanks to its mandibular skull joints, especially the elastic mandibular symphysis which permits both dentaries to be rotated independently in two planes. This flexible jaw, which made the titanic body sizes of baleen whales possible, is not present inearly whales and most likely evolved within Mysticeti.[5]
Many primitiveproboscideans belonging to the groupElephantiformes have a greatly elongated mandibular symphysis. This was lost in many later groups, including modernelephants.[6]
This article incorporates text in thepublic domain frompage 172 of the 20th edition ofGray's Anatomy(1918)
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