Mandibular symphysis in the context of Mental tubercle


Mandibular symphysis in the context of Mental tubercle

⭐ Core Definition: Mandibular symphysis

In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular 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). It is not a true symphysis as there is no cartilage between the two sides of the mandible.

This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. The lowest (most inferior) point of the mandibular symphysis—commonly referred to as the chin—is called the menton.

↓ Menu
HINT:

In this Dossier

Mandibular symphysis in the context of Maxilla

In vertebrates, the maxilla (pl.: maxillae /mækˈsɪl/) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine. This is similar to the mandible (lower jaw), which is also a fusion of two mandibular bones at the mandibular symphysis. The mandible is the movable part of the jaw.

View the full Wikipedia page for Maxilla
↑ Return to Menu

Mandibular symphysis in the context of Mastodon

A mastodon (from Ancient Greek μαστός (mastós) 'breast' and ὀδούς (odoús) 'tooth') is a member of the genus Mammut (German for 'mammoth'), which was endemic to North America and lived from the late Miocene to the early Holocene. Mastodons belong to the order Proboscidea, the same order as elephants and mammoths (which belong to the family Elephantidae). Mammut is the type genus of the extinct family Mammutidae, which diverged from the ancestors of modern elephants at least 28 million years ago, during the Oligocene.

Like other members of Mammutidae, the molar teeth of mastodons have zygodont morphology (where parallel pairs of cusps are merged into sharp ridges), which strongly differ from those of elephantids. In comparison to its likely ancestor Zygolophodon, Mammut is characterized by particularly long and upward curving upper tusks, reduced or absent tusks on the lower jaw, as well as the shortening of the mandibular symphysis (the frontmost part of the lower jaw), the latter two traits also having evolved in parallel separately in elephantids. Mastodons had an overall stockier skeletal build, a lower-domed skull, and a longer tail compared to elephantids. Fully grown male M. americanum are thought to have been 275–305 cm (9.02–10.01 ft) at shoulder height and from 6.8 to 9.2 t (6.7 to 9.1 long tons; 7.5 to 10.1 short tons) in body mass on average. The size estimates suggest that American mastodon males were on average heavier than any living elephant species; they were typically larger than Asian elephants and African forest elephants of both sexes but shorter than male African bush elephants.

View the full Wikipedia page for Mastodon
↑ Return to Menu