TYPES OF MAMMALIAN TEETH

TYPES OF MAMMALIAN TEETH

  • Mammals have four kinds of teeth
  • The incisors are found at the front of the jaw
  • They are sharp-edged and are used for biting
  • The canines are located at the sides of the jaw
  • They are pointed and are used for tearing and piercing
  • The premolars are next to the canines and the molars are at the back of the jaw
  • Both premolars and molars are used for crushing and grinding
  • Teeth are replaced only once in a lifetime
  • The first set is the milk or deciduous teeth
  • These are replaced by the second set or the permanent teeth
  • Dentition refers to the type of teeth, the number and their arrangement in the jaw
  • A dental formula shows the type and number of teeth in each half of the jaw
  • The number of teeth in half of the upper jaw is represented above a line and those on the lower jaw below the line
  • The first letter of each type of teeth is used in the formula i.e

i = incisors, c = canines, pm = premolars and m = molars

  • The total number is obtained by multiplying by two (for the two halves of each jaw)

Adaptation of Teeth to Feeding

  • In general, incisors are for cutting, canines for tearing while premolars and molars are for grinding
  • However, specific modifications are observed in different mammals as an adaptation to the type of food they eat
  • Teeth of Herbivores
  • Incisors are long and flat with a sharp chisel¬like edge for cutting
  • The enamel coating is thicker in front than at the back so that as the tooth wears out, a sharp edge is maintained
  • Canines are reduced or absent
  • If absent, the space left is called the diastema
  • The diastema allows the tongue to hold food and push it to the grinding teeth at the back of the mouth

Premolars and molars:

  • These are transversely ridged
  • The ridges on the upper teeth fit into grooves on the lower ones
  • This gives a sideways grinding surface
  • The teeth of herbivores have open roots i.e

, wide opening into the pulp cavity

  • This ensures a continued adequate supply of food and oxygen to the tooth
  • In some herbivores, such as rabbits and elephants, the incisors continue to grow throughout life
See also  CLASSIFICATION OF ANIMALS AND ORGANIZATION OF LIFE

Teeth of Carnivores

  • Incisors are reduced in size and pointed
  • They are well suited for grasping food and holding prey
  • Canines are long, pointed and curved
  • They are used for piercing and tearing flesh as well as for attack and defence

Premolars and molars: In general, they are long and longitudinally ridged to increase surface area for crushing

Carnassial Teeth: These are the last premolars on the upper jaw and the first molars on the lower one

  • They are enlarged for cutting flesh
  • They act as a pair of shears
  • They also crush bones
  • The teeth of carnivores have closed roots i.e

, only a very small opening of the pulp cavity to allow food and oxygen to keep teeth alive

  • Once broken, no re-growth can take place

Teeth of Omnivores

  • Incisors have a wide surface for cutting
  • Canines are bluntly pointed for tearing
  • Premolars and molars have cusps for crushing and grinding
  • The premolars have two blunt cusps while the molars have three to four.

The tooth consists of two main parts:

Crown: The portion above the gum; it is covered by the enamel

Root: The portion below the gum; it is covered by the cement

  • The tooth has two roots

Neck: Is the region at the same level with the gum

  • It forms the junction between the crown and the root
  • It is covered by enamel

Incisors and canines have one root only

  • Premolars have one or two roots while molars have two to three roots each
  • Internally, the bulk of the tooth is made up of dentine which consists of living cells and extends to the root
  • It is composed of calcium salts, collagen and water
  • It is harder than bone but wears out with use
  • This is why it is covered by enamel which is the hardest substance in a mammal’s body

Pulp Cavity: Contains blood vessels which provide nutrients to the dentine and remove waste products

  • It also contains nerve endings which detect heat, cold and pain

Cement: Fixes the tooth firmly to the jaw bone

 

Also See

HETEROTROPHISM

ENZYMES

POLYSACCHARIDES

PROCESS OF PHOTOSYNTHESIS

NUTRITION IN PLANTS

 

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