Mastication in animals

Mastication in animals

Extensive chewing of the feed causes mechanical reduction in the size of the food, this is known as mastication in animals. The finely divided food particles provide greater surface area for enzymatic action and proper mixing with saliva for easy swallowing. This act is achieved by deduction and occlusion of both the upper and lower molar teeth.

Temporo-mandibular joint is involved. Hence, lateral forward and backward movement is possible. Most of the animals masticate on one side at a time due to the anatomical arrangement of the dental table (wider upper jaw and narrower lower jaw).

Molar teeth are chisel shaped with the arrangement of inner most lower teeth and outer most teeth. Both are sharp edged.

Importance of mastication

1. In herbivores mastication is of greater significance due to the coarse bulky nature of food.
2. In ruminants, only during re-mastication the food is thoroughly ground.
3. In herbivores, mastication of food material is by lateral movement of the lower jaw and to-and-fro movement.
4. In herbivores, the upper jaw is wider than the lower jaw and mastication of food occur on only one side at a time.
5. The molar teeth are chisels shaped with sharp edged lower teeth pointed towards inner side and that of upper teeth towards outer side. Incisor teeth are used to cut and lacerate the food
6. In ruminants, the upper incisors are absent, but modified as dental pad and in the lower jaw they are loosely and obliquely placed in the sockets.
7. Grazing
   • Traditional grazers ( sheep, cattle)
     • Grass and roughage eaters.
     • Mostly graze on monocotyledons
     • Use their small mouth and long tongue to grasp grass and hay.
     • Tongue is curved around the grass
   • Browser ruminants ( deer, giraffe and moose)
     • Graze on dicotyledons
     • Have large mouth opening and use their incisors to gnaw on fruits and flowers, trees.
   • Intermediary – opportunistic feeders (goat)
     • Adapt to both the pattern of feeding.
     • They prefer low fiber dicotyledons .
     • Preferred food can be sought by climbing
8. Bovine
   • Keratinized papillae of the bovine helps in the passage of food in the oral cavity.
   • As the tongue pushes the cell grass between the lower incisors and upper dental pad, simultaneous mandibular severing reduces the size of the particles.
   • As rumination is the predominant activity, they spend less time in initial mastication.
9. Sheep and goat
   • Mandibular grinding
10. Horse
    • Incisors thrust the feed into the oral cavity with the propulsive movement of mandible, maceration of grass at its base is achieved.
    • Masticate thoroughly prior to swallowing.
11. Omnivores occupy a position between herbivores and carnivoresin the aspect of timing.
12. Pig
    • Use incisors, tongue and propulsive movements of head for mastication.
    • Rhodents have the unique property of mastication due to their ability to shift their teeth in a proplineal pattern.
13. In carnivores, mastication is imperfectly performed by vertical movement of the lower jaw.
14. Dog and cat
    • Mastication is done by teeth with food in oral cavity by propulsive head and mandibular movements.
    • In cats, papillae of the tongue (dorsal lingual spicules) help in pushing the feed into the oral cavity.
15. In carnivores and omnivores, the upper and lower jaws are equal width and the teeth are relatively simple.  

Drinking

1. Dogs and cats
   • Fluid is drawn into the oral cavity by the rapid extension and retraction of the tongue by making the free end of the tongue as laddle like structure to convey the liquid into the mouth.
2. Horse, Bovine, Sheep and Goat
   • Drinking of fluid is by suction by creating negative pressure by keeping closed mouth beneath the fluid and tongue.

Suckling

Suckling is effected by creating negative pressure in the mouth largely by the back ward movement of base of the tongue. Milk is forced from the teat into the mouth due to pressure gradient.

Function and mechanism of mastication

Functions of mastication

1. Physical breakdown increases the surface area of food, which improves the microbial digestion.
2. Assist in appreciating the flavor of the food.
3. Improves salivary and gastric activities.
4. Initial digestion of carbohydrates is facilitated.
5. Contributes to dilution and buffering of ruminoreticular fluid.

Mechanism of mastication

1. Reflex activity under the control of CNS.
2. Mastication is basically a voluntary act but usually takes place involuntarily.
3. Mastication reflex or chewing reflex is the rhythmic movements of mandible.
4. Lowering pf mandible due to extension of tongue( mainly in bovine) is known as LINGUO MANDIBULAR REFLEX.
5. Stimuli for masticatory reflex is the presence of food in the oral cavity.
6. These are receptors in tongue and oral mucosa which initiates mastication by the sense of food.
7. Sensory impulses are carried via trigeminal, facial, and glossopharyngeal nerves to brain stem.
8. Efferent via trigeminal supplied to mastigatory muscles.
9. This in turn causes rhythmic movement of the mandible in relation to the maxilla.
10. This results in shearing and crushing of food.
11. The main mastigatory muscles include temporalis with the assistance from massetor muscle for shearing and massetor with the assistance from pterygoid muscles for grinding.