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Encyclopedia > Mastication

Mastication or chewing is the process by which food is mashed and crushed by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by the cheek and tongue. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food. Types of teeth Molars are used for grinding up foods Carnassials are used for slicing food. ... This article or section does not cite its references or sources. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Look up Cheek in Wiktionary, the free dictionary The Cheeks are the fleshy area of the face below the eyes and between the nose and the left or right ear, the skin being suspended by the chin and the yaws. ... For other uses, see Tongue (disambiguation). ... Carbohydrates (literally hydrates of carbon) are chemical compounds that act as the primary biological means of storing or consuming energy, other forms being fat and protein. ...


After chewing, the food (now called a bolus) is swallowed. It enters the esophagus and continues on to the stomach, where the next step of digestion occurs. Look up bolus in Wiktionary, the free dictionary. ...


Cattle and some other animals, called ruminants, chew food more than once to extract more nutrients. After the first round of chewing, this food is called cud. Binomial name Bos taurus Linnaeus, 1758 Cattle (often called cows in vernacular and contemporary usage, or kye as the Scots plural of cou) are domesticated ungulates, a member of the subfamily Bovinae of the family Bovidae. ... Families Antilocapridae Bovidae Cervidae Giraffidae Moschidae Tragulidae A ruminant is any hooved animal that digests its food in two steps, first by eating the raw material and regurgitating a semi-digested form known as cud, then eating the cud, a process called ruminating. ... Cud is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. ...

Contents

Muscles of mastication

Mastication is accomplished through the activity of the four muscles of mastication. Mastication is a name for the process of breaking up of food and mixing it with saliva. ...

Unlike most of the other facial muscles, which are innervated by the facial nerve, or CN VII, the muscles of mastication are all innervated by the trigeminal nerve, or CN V. More specifically, they are innervated by the mandibular branch, or V3. This is a testament to their shared embryological origin from the first branchial arch. The muscles of facial expression, on the other hand, derive from the second branchial arch. In human anatomy, the masseter is one of the muscles of mastication. ... The temporalis muscle is one of the muscles of mastication. ... The medial pterygoid is a muscle of mastication with two heads. ... The lateral pterygoid (or external pterygoid) is a muscle of mastication with two heads. ... The facial nerve is seventh of twelve paired cranial nerves. ... The facial nerve is the seventh (VII) of twelve paired cranial nerves. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... The trigeminal nerve (the fifth cranial nerve, also called the fifth nerve or simply V) is responsible for sensation in the face. ... The mandibular nerve is the third branch (V3) of the trigeminal nerve. ... The mandibular nerve is the third branch (V3) of the trigeminal nerve. ... In the development of vertebrate animals, the branchial arches (or pharyngeal arches) develop during the fourth and fifth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx. ... The facial muscles are a group of skeletal muscles innervated by the facial nerve that, among other things, control facial expression. ...


In humans, the mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint, an extremely complex joint which permits movement in all planes. The muscles of mastication originate on the skull and insert into the mandible, thereby allowing for jaw movements during contraction. The mandible is the only bone that moves during mastication and other activites, such as talking. It has been suggested that this article or section be merged with jaw. ... The temporal bones (os temporales) are situated at the sides and base of the skull. ... The temporomandibular joint (From the Latin for too much jaw) is a diarthrodial joint that connects the condyle of the mandible (lower jaw) to the temporal bone at the side of a skull. ...


Each of these primary muscles of mastication is paired, with each side of the mandible possessing one of the four. 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.


The chewing cycle

Mastication is a repetitive sequence of jaw opening and closing with a profile in the vertical plane called the chewing cycle. Mastication consists of a number of chewing cycles. The human chewing cycle consists of three phases:


1. Opening phase: the mouth is opened and the mandible is depressed.


2. Closing phase: the mandible is raised towards the maxilla.


3. Occlusal or intercuspal phase: the mandible is stationary and the teeth from both upper and lower arches approximate.


Mastication motor program

Mastication is primarily an unconscious act, but can be mediated by higher conscious input. The motor program for mastication is an hypothesized central nervous system function by which the complex patterns governing mastication are created and controlled.


It is thought that feedback from proprioceptive nerves in teeth and the temporomandibular joints govern the creation of neural pathways, which in turn determine duration and force of individual muscle activation (and in some cases muscle fiber groups as in the masseter and temporalis). Proprioception (from Latin proprius, meaning ones own) is the sense of the position of parts of the body, relative to other neighbouring parts of the body. ...


The motor program continuously adapts to changes in food type or occlusion [1].


It is thought that conscious mediation is important in the limitation of parafunctional habits as most commonly, the motor program can be excessively engaged during periods of sleep and times of stress. It is also theorized that excessive input to the motor program from myofascial pain or occlusal imbalance can contribute to parafunctional habits. A para-functional habit or parafunctional habit is the habitual exercise of a body part in a way that is other than the most common use of that body part. ... A para-functional habit or parafunctional habit is the habitual exercise of a body part in a way that is other than the most common use of that body part. ...


Notes

  1. http://jn.physiology.org/cgi/content/full/92/2/773 -Influence of age on adaptability of human mastication.

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