Knowing the muscle layers can help doctors perform better surgeries
Human anatomy still contains some surprises. Researchers at the Swiss University of Basel recently discovered a part of the human body that had not been described before, which is a deep layer of jaw muscles that raise the lower jaw, and are necessary for chewing, and they described this layer in detail for the first time.
Senior author Dr. Jens Christoph Torbe, Professor and Physician at the Dental Center at the University of Basel in Switzerland, said in a statement Press release of the university on December 20 – “Although it is generally assumed that anatomical research in the past 100 years has left no effort unchanged, our discovery is somewhat similar to the discovery by zoologists of a new species of vertebrate.”
This discovery relates to the masseter muscle, which is one of the four muscles of mastication. It consists of superficial muscle fibers and deep muscle fibers. It is a small muscle, but it is one of the strongest muscles in the body, and it covers the branch of the coronary process of the jawbone. Modern anatomy textbooks describe the masseter muscle as having two layers: one deep, the other superficial.
The muscle lifts the lower jaw up, closing the mouth forcefully. The force of contraction and action of the two muscles: the temporalis muscle and the masseter muscle, is sufficient for a person to attach to a rope holding between the applied teeth, meaning that they bear the weight of the body.
The study authors wrote – in new search Published December 2 in the online edition of Annals of Anatomy due for publication in the February 2022 issue – “However, some historical texts suggest that there may be a third layer as well, but they are inconsistent very much in terms of its location.” So the team decided to check whether the prominent jaw muscle might contain an ultra-deep occult layer, as the historical texts indicate.
Important clinical discovery
According to to report Published on Live Science, they autopsied 12 cephalopods preserved in formaldehyde, performed cross-sectional examinations of 16 “new” cadavers (recent corpses not preserved in formaldehyde), and reviewed an MRI scan.
Through these examinations, they identified the third – “anatomically distinct” layer of the masseter muscle. This deep layer extends from the zygomatic process, a bony bump that forms part of the “cheekbone” and can be felt just in front of the ear, to the coronal process, a triangular process on the lower jawbone.
“This deep part of the masseter muscle can be clearly distinguished from the other two layers in terms of its course and function,” Dr. Silvia Mizzi, a senior lecturer at the Department of Biomedicine at the University of Basel in Switzerland, said in the press release.
Based on the arrangement of the muscle fibers, the muscle layer likely helps stabilize the mandible by “lifting and pulling” the coronal process, the team wrote in their report. “In fact, the newly discovered muscle layer is the only part that can pull the jawbone back,” says Maisie.
In their research paper, the team proposed naming the newly discovered muscle layer as (Musculus masseter pars corridea), meaning “the coronary part of the masseter muscle.” This discovery may be important in the clinical context, because knowledge of the muscle layers can help doctors perform better surgeries in that area of the jaw, and treat conditions that include the joint that connects the jawbone to the skull.
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