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Mastication
 
 
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Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
 and it increases the surface area of foods to allow more efficient break down by enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s. During the mastication process, the food is positioned between the teeth for grinding by the cheek
Cheek

Cheeks constitute the area of the face below the eyes and between the nose and the left or right ear.It is fleshy in humans and other mammals, the skin being suspended by the chin and the jaws, and forming the lateral wall of the human mouth, visibly touching the cheekbone below the eye....
 and tongue
Tongue

The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing . It is the primary organ of taste. Much of the upper surface of the tongue is covered in papillae and taste buds....
. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food.






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Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion
Digestion

Digestion is the mechanical and chemical breaking down of food into smaller components, to a form that can be Absorption, for instance, by a blood stream....
 and it increases the surface area of foods to allow more efficient break down by enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s. During the mastication process, the food is positioned between the teeth for grinding by the cheek
Cheek

Cheeks constitute the area of the face below the eyes and between the nose and the left or right ear.It is fleshy in humans and other mammals, the skin being suspended by the chin and the jaws, and forming the lateral wall of the human mouth, visibly touching the cheekbone below the eye....
 and tongue
Tongue

The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing . It is the primary organ of taste. Much of the upper surface of the tongue is covered in papillae and taste buds....
. As chewing continues, the food is made softer and warmer, and the enzymes in saliva begin to break down carbohydrates in the food. After chewing, the food (now called a bolus
Bolus (digestion)

In digestion, a bolus is a mass of food that has been Mastication and swallowed. Once a bolus reaches the stomach, digestion begins.* Compare to chyme....
) is swallowed. It enters the esophagus and continues on to the stomach, where the next step of digestion occurs.

Cattle
Cattle

Cattle, colloquially referred to as cows, are domestication ungulates, a member of the subfamily Bovinae of the family Bovidae. They are raised as livestock for meat , dairy products , leather and as draft animals ....
 and some other animals, called ruminant
Ruminant

Physiologically, a ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach, known as the rumen, then regurgitating the semi-digested mass, now known as cud, and chewing it again....
s, chew food more than once to extract more nutrients. After the first round of chewing, this food is called cud
Cud

Cud is a portion of food that returns from a ruminant's stomach in the mouth to be chewed for the second time. More accurately, it is a Bolus of semi-degraded food regurgitation from the reticulorumen of a ruminant....
.

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).

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

It is thought that conscious mediation is important in the limitation of parafunctional habit
Parafunctional habit

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....
s 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 habit
Parafunctional habit

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....
s.

In other animals


Chewing is largely an adaptation for mammalian
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
 herbivory. Carnivores
Carnivore

A carnivore , meaning 'meat eater' , is any animal with a diet consisting mainly of meat, whether it comes from animals living or dead .In a more general sense, an animal may be considered a carnivore if it prefers feeding on animal matter over plant matter....
 generally chew very little or swallow their food whole or in chunks, a fact to which many dog
Dog

The dog is a domesticated subspecies of the Gray Wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties....
 and cat
Cat

The cat , also known as the Domestication cat or house cat to distinguish it from other Felinae and Felidae, is a small predationy carnivore species of crepuscular mammal that is valued by humans for its companionship and its ability to hunt vermin, snakes, scorpions, and other unwanted household pests....
 owners can attest. This act of gulping food without chewing has inspired the English idiom
Idiom

An idiom is a phrase whose meaning cannot be determined by the literal definition of the phrase itself, but refers instead to a figurative language meaning that is known only through common use....
 "wolfing it down".

Ornithopods
Ornithopod

Ornithopods are a group of ornithischia dinosaurs that started out as small, bipedal cursorial grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape....
, a group of dinosaurs
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
 including the Hadrosaurids
Hadrosaurid

Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus....
 ("duck-bills"), developed teeth analogous to mammalian molars
Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
 and incisors
Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below....
 during the Cretaceous
Cretaceous

The Cretaceous , usually abbreviated K for its German translation Kreide, is a geologic period from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period....
 period; this advanced, cow-like dentition allowed the creatures to obtain more nutrients from the tough plant life. This may have given them the advantage needed to usurp the formidable sauropods
Sauropoda

Sauropoda , or the sauropods , are an Order or clade of saurischian dinosaurs. They notable for the enormous sizes attained by some species, and the group includes many of the largest animals to have ever lived on land....
, who depended on gastroliths
Gastrolith

Gastroliths are Rock , which are or have been held inside the Gastrointestinal tract of an animal. Among living vertebrates, gastroliths are common among Herbivore birds, crocodiles, alligators, seals and Sea Lion....
 for grinding food, from their ecological niches. They eventually became some of the most successful animals on the planet until the Cretaceous–Tertiary extinction event wiped them out.

In machinery

The process of mastication has, by analogy, been applied to machinery. The U.S. Forest Service uses a machine called a masticator to "chew" through brush and timber in order to clear firelines in advance of a wildfire.

See also

  • Gnathology
    Gnathology

    Gnathology is the study of mastication, including its physiology, functional disturbances, and treatment. Because it is not part of dentistry training, most is learned by participating in 'study clubs" with mentors with much experience....


External links

  • Neuromuscular dentistry
    Neuromuscular dentistry

    Neuromuscular dentistry is a medical paradigm in which TM Joints, Mastication#Muscles_of_masticationand Central nervous system mechanisms follow generic physiologic and anatomic laws applicable to all Musculoskeletal system....