| Molar (tooth) | |
|---|---|
 |
|
| A lower wisdom tooth after extraction. | |
 |
|
| Permanent teeth of right half of lower dental arch, seen from above. | |
| Latin | dentes molares |
| Gray's | subject #242 1118 |
| Artery | posterior superior alveolar artery |
| Dorlands/Elsevier | d_08/12285848 |
Molars are the rearmost and most complicated kind of tooth in most mammals. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Gray's Anatomy the Respiratory apparatus ( Apparatus Respiratorius Respiratory system Respiratory apparatus Arteries are Blood vessels that carry blood away from the Heart. The posterior superior alveolar artery ( posterior dental artery) is given off from the Internal maxillary, frequently in conjunction with the Infraorbital Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands In many mammals they grind food; hence the Latin name mola, "millstone". Millstones or mill stones are used in Windmills and Watermills including Tide mills for grinding Wheat or other grains
Contents |
Human molars
Adult humans have twelve molars, in four groups of three at the back of the mouth. The third (rearmost) molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the surface of the gum at about the age of twenty, although this varies from individual to individual. Ethnicity can also have an impact on the age at which this occurs, with statistical variations between groups.
The types of molars in the human mouth are:
- maxillary first molars, maxillary second molars, and maxillary third molars
- mandibular first molars, mandibular second molars, and mandibular third molars
Molars among species
Molars differ considerably from one species to another, so there are many terms describing them:
- Tribosphenic: This kind is found in insectivores and young platypuses (adults have no teeth). The maxillary first molar is the Tooth located laterally (away from the midline of the Face) from both the Maxillary second premolars of the Mouth The maxillary second molar is the Tooth located laterally (away from the midline of the Face) from both the Maxillary first molars of the Mouth The maxillary third molar, commonly known as a wisdom tooth, is the Tooth located laterally (away from the midline of the Face) from both the The mandibular first molar or six-year molar is the Tooth located distally (away from the midline of the Face) from both the Mandibular second The mandibular second molar is the Tooth located distally (away from the midline of the Face) from both the Mandibular first molars of the Mouth The mandibular third molar, commonly known as a wisdom tooth, is the Tooth located distally (away from the midline of the Face) from both the Mandibular An insectivore is a type of carnivore with a diet that consists chiefly of Insects and similar small creatures The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. Upper molars look like three-pointed mountain ranges; lowers look like two peaks and a third off to the side.
- Quadrate: This kind is found in humans and various other species. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Four cusps are arranged in a rectangle; there may be a fifth.
- Bunodont: The cusps, instead of being sharp peaks, are rounded hills. The entire tooth is covered in enamel, and is most common among omnivores such as the pig, the bear and humans. Pigs, also called hogs or' swine', are Ungulates which have been domesticated as sources of food leather and similar products since ancient times Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus
- Hypsodont: There is a lot of enamel and dentine above the gumline and the top of the pulp. This kind of molar is found in mammals that wear their teeth a lot, such as the horse. The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae.
- Zalambdodont: The tooth has two ridges that meet at an angle, forming the letter lambda.
- Dilambdodont: Like zalambdodont, but there are two lambdas on one tooth.
- Lophodont: The tooth has a few ridges perpendicular to the jaw.
- Selenodont: The tooth has a crescent-shaped ridge or ridges.
- Loxodont: The tooth has several parallel oblique ridges on its surface. The elephant Loxodonta is named for this feature. Elephants ( family: Elephantidae) are large land Mammals of the order Proboscidea.
Tribosphenic molar
The molar design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar. This design of molar has two important features: the trigonid, or shearing end, and the talonid, or crushing heel. In modern mammals that have tribosphenic molars the trigonid is towards the front and the talonid towards the rear.
The tribosphenic design appears in all groups of mammals. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Some paleontologists believe that it developed independently in monotremes, rather than being inherited from an ancestor that they share with with marsupials and placentals; but this idea has critics and the debate is still going on. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals [1]
Also some Jurassic mammals, such as Shuotherium and Pseudotribos, have "reversed tribosphenic" molars in which the the talonid is towards the front. The Jurassic is a geologic period and system that extends from about Ma (million years ago to Ma that is from the end of the Triassic to the beginning Pseudotribos is an Extinct Genus of Mammal from the Middle Jurassic some 165 million years ago of China. This variant is regarded as an example of convergent evolution[2]
Additional images
 Molar 47 (left), molar 46 and premolar 45(right) |
 Mouth (oral cavity) |
 Left maxilla. Convergent evolution describes the acquisition of the same biological trait in unrelated lineages Outer surface. |
 Base of skull. Inferior surface. |
 The permanent teeth, viewed from the right. |
See also
References
- ^ Stokstad, E. Incisors (from Latin incidere, "to cut" are the first kind of Tooth in Heterodont Mammals They are located in the Premaxilla "Cuspid" redirects here For the heart valves see Bicuspid valve and Tricuspid valve. (January 2001). "Tooth Theory Revises History of Mammals". Science 291: 26. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Luo, Zhe-Xi (November 2007). "Convergent dental adaptations in pseudo-tribosphenic and tribosphenic mammals". Nature 450 (450): 93-97. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
External links
For pictures of various molars see The Diversity of Cheek Teeth.
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic