Description of Mandibles
Question One
What is Mandible?
The mandible is the strongest, largest, and lowest jawbone in the human face holding the lower teeth in place. The bone is the moving part of lower jaws during the feeding process, making all the mastication muscles attached to it (Staszyk et al., 2015). As the only moveable bone of the skull, mandible sits beneath the maxilla, which is the upper fixed bone of the jaw formed from a fusion of two maxillary bones. Mandible discounts the ossicles of the middle ear. The term mandible is derived from a Latin word mandibula, which literary means one used for chewing. It is the only bone in the skull that does not articulate with entire adjacent skull bones through sutures.
Question Two
Description of Mandibles
Mandibles are singular bones with a distinctive horseshoe shape, which is symmetrical on both sides. Mandibles are formed in the prenatal development from a fusion of the right and left mandibular prominences. Mandibles consist of two major parts, the body mostly found at the front and ramus located in the right and left, meeting the body at a gonial angle (Staszyk et al., 2015). The body of mandible bone has a curved structure, which gives the front part the chin structure. From the inside, mandibles have a concave shape at the lower part of the symphysis giving the origin of the genioglossus, which is one of the paired extrinsic tongue muscles. The ramus projects perpendicularly upwards from the mandible angle, and each ramus are composed of the head, coronoid process, which is the site temporalis muscles are attached, and the neck supporting temporalis process and the head. A mandible articulates dentally with the upper jaw in the viscerocranium through the teeth when an individual closes the mouth. The bone also articulates to neurocranium through the temporal bone, which forms the temporomandibular joint.
Mandible occurs during the sixth week of intrauterine development, and it continually changes during the development of an individual’s life cycle. Hene, when the teeth begin to form in the lower jaw, the bone elongate and widen, causing the gonial angle to decrease. The primary nerve linked to mandibles is the inferior alveolar nerve entering the mandibular foramen providing sensation to the lower teeth. Several other muscles are originating from the jawbone. Some of the muscles include mentalis, orbicularis oris, depressor labii inferioris, depressor anguli oris, superior pharyngeal constrictor, and many more. Some muscles such as the platysma, superficial masseter, deep master, and inferior head of the lateral pterygoid inserts on the mandible. According to human anatomy, males generally have square and most prominent bones as opposed to females. The difference in size is due to the larger size of the mental protuberance in males because they have a decreased gonial angle.
Question Three
How the Mandible Moves
Mandibular movements are predominantly orthal as forward translation occurs in mouth opening, while lateral deflections occur in both closing and opening phases of the mouth. The small deflections in the opening and closing phases are related to the existence of bolus bearing and balancing sides of the jaws, as chewing is not bilateral (“Unusual Anatomy of a Second Maxillary Molar – a Rare fourRoot Configuration Case Report,” 2016). The deflections are linked to the shift of both condyles towards a particular side. Condyles refer to the occipital bone underneath protuberances in human mouthpart, aiding in the articulation with superior facets. During the chewing process, food is transferred from side to side in a reversal chewing direction during the opening phase. However, the reversal chewing is only frequent as the chewing process near its end.
The movement of mandibles is based on the activities of the mastication muscles, which is the chewing process. The first muscle responsible for mandibles movements is the masseter, which is a powerful muscle located in the cheek area. The muscle raises the lower jaw through an elevation of the mandible during the chewing process. Through the help of temporalis muscles, aids in the closing and opening of the mouth during the chewing process by curling back around an approximate location of the ear. During the process of alternating food in the mouth from side to side and forward, the jaw closes with the help of medial pterygoid muscle. The opening of the jaw is assisted by lateral pterygoid, which lowers the jaw from side to side. The fundamental pattern of mandibles movement produced during the process of chewing represents a chewing stroke. The lower jaw’s attachment to the skull by the temporomandibular joint, aids in a wide range of lower jaw movements.
Question Four
Teeth Carried by the Mandible
According to dental anatomy, mandibles begin to form in the fetus stage, and in the baby stage, there are 20 primary teeth. Among the primary teeth, ten are found in the upper jaw while the rest are in the lower jaw. In adults, 16 are in the upper jaw, and the other 16 are in the lower jaw. Most of these teeth have distinguishing features (“Unusual Anatomy of a Second Maxillary Molar – a Rare fourRoot Configuration Case Report,” 2016). The term maxillary is used to describe teeth in the upper jaw, while mandibular are teeth in the lower jaw. There are no premolars in primary teeth of children of about 13 years, but in adults, the lower jaw composed of 16 teeth, six molars, two canines, four incisors, four premolars. Teeth are attached to the jaw bone through the alveolar process by fibrous ligaments known as the periodontal ligaments. The teeth in the lower jaw of humans are the first to erupt, and the upper teeth follow after approximately two months.
Question Five
Functions of the Mandible
The mandible serves along with the upper jaw as an essential structural and protective component of the jaw. It forms the house of all lower teeth where significant nerves and muscles run through or emerge from it. The mandible is entirely involved in the chewing process and most movements in the mouth that aid in the mastication process (Staszyk et al., 2015). The front-most section of the mandibular is narrow to hold the front teeth in place, while the hind part is more extensive and flatter, containing teeth responsible for the chewing process. Mostly, the hid teeth have deep grooves and broad surfaces for easy grinding of food. During the chewing process, mandibular ramus and the condylar process articulate with a temporal bone to create room for mobility through the temporomandibular joint. The movement of the lower bone of the jaw is responsible for opening and closing of the mouth, allowing the chewing process to take place.
Question Six
Muscles of Mastication
Mastication refers to the process of chewing and grinding of food into small particles for easy swallowing and digestion. The entire process of digestion is aided by teeth, tongue, and specific movements of the temporomandibular joint from masticatory muscles. Mandibular nerves supply mastication as the whole muscles; it has four major mastication muscles support the chewing (Parveen, 2018). First is the masseter muscle; it is responsible for the mandible elevation and side-to-side movements. Second is the temporal muscle; it retrudes and elevates mandibles and helps the pterygoid tissue later move. The third is the medial pterygoid muscle, which protrudes and elevates the bone for a lateral excursion. The last is the lateral pterygoid muscle, which protrudes and depresses the mandible to move it laterally during the chewing process.
References
Parveen, S. (2018). A Morphological Study of Coronoid Process of Adult Human Dry Mandibles. Journal Of Medical Science And Clinical Research, 6(4). https://doi.org/10.18535/jmscr/v6i4.27
Staszyk, C., Suske, A., & Pöschke, A. (2015). Equine dental and periodontal anatomy: A tutorial review. Equine Veterinary Education, 27(9), 474-481. https://doi.org/10.1111/eve.12317
Unusual Anatomy of a Second Maxillary Molar – a Rare fourRoot Configuration Case Report. (2016), 1(2). https://doi.org/10.20431/2456-0030.0102003