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TYPES OF MAMMALIAN TEETH

TYPES OF MAMMALIAN TEETH

  1. Mammals have four kinds of teeth
  2. The incisors are found at the front of the jaw
  3. They are sharp-edged and are used for biting
  4. The canines are located at the sides of the jaw
  5. They are pointed and are used for tearing and piercing
  6. The premolars are next to the canines and the molars are at the back of the jaw
  7. Both premolars and molars are used for crushing and grinding
  8. Teeth are replaced only once in a lifetime
  9. The first set is the milk or deciduous teeth
  10. These are replaced by the second set or the permanent teeth
  11. Dentition refers to the type of teeth, the number and their arrangement in the jaw
  12. A dental formula shows the type and number of teeth in each half of the jaw
  13. The number of teeth in half of the upper jaw is represented above a line and those on the lower jaw below the line
  14. 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
See also  DIGESTIVE SYSTEM | HYDRA, EARTHWORM, INSECTS, BIRD, MAN, TAPEWORM & PLANARIA

 

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

 

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.
See also  ALLERGIC REACTIONS

 

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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