Mandibular division of the trigeminal nerve. There are four classical muscles of mastication. All four move muscles of mastication pdf jaw laterally. The muscles of mastication originate on the skull and insert into the mandible, thereby allowing for jaw movements during contraction.
Each of these primary muscles of mastication is paired, with each side of the mandible possessing one of the four. The mandible is the only bone that moves during mastication and other activities, such as talking. While these four muscles are the primary participants in mastication, other muscles are usually if not always helping the process, such as those of the tongue and the cheeks. This page was last edited on 12 January 2018, at 21:15.
There are two groups of muscles of the tongue. The four intrinsic muscles alter the shape of the tongue and are not attached to bone. The four paired extrinsic muscles change the position of the tongue and are anchored to bone. The underside of a human tongue, showing its rich blood supply. This division is along the length of the tongue save for the very back of the pharyngeal part and is visible as a groove called the median sulcus. The average weight of the human tongue from adult males is 70g and for adult females 60g.
The four intrinsic muscles act to change the shape of the tongue, and are not attached to any bone. The four extrinsic muscles act to change the position of the tongue, and are anchored to bone. The four extrinsic muscles originate from bone and extend to the tongue. Their main functions are altering the tongue’s position allowing for protrusion, retraction, and side-to-side movement. It is also known as the tongue’s “safety muscle” since it is the only muscle that propels the tongue forward. The chondroglossus is often included with this muscle. Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length.
This provides shape and helps facilitate speech, swallowing, and eating. The superior longitudinal muscle runs along the upper surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. The inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle. The vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles. The floor of the mouth also receives its blood supply from the lingual artery. The tongue can also divide itself in dorsal and ventral surface.
The dorsal surface is a stratified squamous keratinized epithelium which is characterized by numerous mucosal projections called papillae. The lingual papillae covers the dorsal side of the tongue towards the front of the terminal groove . The ventral surface is stratified squamous non-keratinized epithelium which is smooth. These lingual swellings quickly expand and cover the tuberculum impar and continue to develop through prenatal development. They form the anterior part of the tongue that makes up two thirds of the length of the tongue.
The line of their fusion is marked by the median sulcus. The boundary between the two parts of the tongue, the anterior from the first arch and the posterior from the third arch is marked by the terminal sulcus. Umami receptor cells are the least understood and accordingly are the type most intensively under research. The tongue is an important accessory organ in the digestive system. The tongue is used for crushing food against the hard palate, during mastication and manipulation of food for softening prior to swallowing. Consequently, the tongue can grind against the hard palate without being itself damaged or irritated.