Prehension, Mastication�& �Rumination, Deglutition �

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Dr. Amar Chaudhary, ^{DVM, MS}

Assistant Professor

Department of Vet. Anatomy, Physiology and Biochemistry

Agriculture and Forestry University,

Rampur, Chitwan, Nepal

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Digestion

Digestion is the process of mechanically & enzymatically break down of complex food into simpler form by the activity of alimentary tract and glandular secretion for absorption of nutrients and elimination of the waste product.

Digestive process begins:

• With the prehension, or taking up of food
• Continues with its mastication (chewing)
• Insalivation (mixing with the salivary secretions)
• Deglutition (swallowing)
• Digestion & absorption
• Assimilation of those food elements that are of nutritive value
• Terminates with defecation
• Excretion of the remaining ingested matter

Factors of Digestion

Mechanical factors

• Prehension ( Taking of food)
• Mastication (Grinding the food)
• Deglutition (Swallowing)
• Regurgitation (Return of the cud from stomach to mouth)
• Rumination (Chewing of cud)
• Remastication (Regrinding)
• Redeglutition (Reswallowing)
• Intestinal motility
• Eructation (Elimination of gases)
• Defecation (Elimination of faecal matters)

Chemical factors

• Digestive enzymes and hormones
• Non-enzymatic chemicals: HCl, HCO₃

Microbiological factors

• Bacteria
• Protozoa
• Fungi

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Prehension, Mastication, Deglutition

• Prehension:

Process of feed & water intake by domestic animals are aided by muzzle, lips, cheek, tongue & teeth is called prehension

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• Mastication:

Feed intake is crushed & divided into small pieces for further smooth digestion & absorption by chewing

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• Deglutition:

Deglutition or swallowing is conveying of food from mouth through the pharynx & oesophagus to stomach. This is under control of a centre in the medulla oblongata and inferior pons

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Rumination, Defecation, Hunger contraction, Thirst and Vomition

• Rumination- In polygastric animals, food once swallowed is taken back to the oral cavity for re-mastication & re -insalivation

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• Defecation: Complex reflex act where the faces are excrete or expelled through the anus

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• Hunger contraction: These are peristaltic waves travelling from cardia to pylorus. They appear before the stomach has completely or partially emptied.

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• Thirst : a sensation referred to the mucous membrane of mouth & pharynx

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• Vomition : spasmodic ejection of the content of stomach through oesophagus and mouth

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Prehension

Process of feed and water intake by domestic animals are aided by muzzle, lip, teeth is called prehensile.

Prehensile organ of Domestic animal

• In Primate, the hands are the prehensile organ
• In Dog and Cats hold their pray with forelimb which is passed into mouth by the head and jaw movement
• In Horse, upper lip, tongue and the incisor teeth are main prehensile organ
• Clefted upper lip in Sheep favors close grazing on contrast the unclefted upper lip in Goat
• In cattle, large strong, rough protrudeable tongue and incisor teeth of lower jaw are the main prehensible organ
• Pointed lower lip function as prehensible organ in swine

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Clefted upper lip in Sheep

pointed lower lip in swine

Prehension (Contd.)

In the Horse:

• prehension is performed by the strong and flexible upper lip and incisor teeth
• When grazing, lips and incisor teeth, cutting or tearing the vegetation seized by jerking movements of the head or neck.

In the Ox:

• not such mobile lips or with upper incisor teeth, Instead it uses its long, muscular tongue to pull the grass or hay into its mouth, cutting it off between the lower incisors and the upper gum by an upward movement of the head and neck.

In the Sheep:

• seizes its food in much the same manner, but it makes use of its mobile lips rather than its tongue in gathering food into the mouth.

Native habit of the pig:

• Burrowing or rooting to find its food has survived the domestication of this species.
• Prehension, however, is accomplished by the movements of the pointed lower lip and is assisted by the teeth and tongue

In the dog and the cat:

• Food is seized by the incisor and canine teeth and brought into the mouth by jerking movements of the head and jaws

Prehension organ in fowls:

is the beak picks up its food in its toothless beak and passes it to the base of the tongue preparatory to swallowing

Prehension (Contd.)

• Drinking is accomplished by the horse, ox, sheep, and pig by sucking the fluid into the mouth by the aid of the tongue and pharynx.
• The lips form a small opening which is dipped beneath the surface of the water, and the tongue moving back and forth like a piston in a cylinder creates a negative pressure in the mouth which causes water to pass into the mouth with the backward thrust of the tongue and to be swallowed with the forward thrust.
• The pharynx serves as a valve in this pumping process.
• The dog and the cat take up liquids by lapping with the tongue.

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Prehension (Contd.)

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• Fowl:
• Drinking consists merely of scooping up the fluid into the lower beak and then elevating the head to permit it to flow by gravitation into the crop or stomach.

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• Pigeon’s :
• Method of drinking, however, more nearly resembles that of the horse or ox than that of other birds.
• This bird thrusts its beak deep into the water and by a very rapid movement of the tongue sucks in the liquid.

Mastication

• Mastication, or chewing, of food by means of grinding teeth so situated in the upper and lower jaws that crush and divide the food substance preparatory to swallowing.
• Mechanism of mastication involves the use of the two jaws, the tongue, and the cheeks.
• The upper jaw is a rigid portion of the head, while the lower jaw is hinged to the skull so that it can be moved in a vertical and to some extent in a lateral against the upper jaw.
• These movements are brought about by the muscles of the jaws.
• There is a pronounced sidewise or lateral movement of the lower jaw in the ruminants (ox and sheep), slightly less in the horse, and still less in the omnivorous pig.
• In the carnivores (dog and cat), there is very little lateral movement

Mastication (contd.)

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• Mastication in the horse, pig, dog, and cat is a single process preparatory to swallowing.
• The dog and cat chew very little, usually bolting their food in relatively large pieces
• In the ruminants, represented by the ox and sheep, this process is divided into two phases:
• Incomplete mastication when the food is first taken, and
• complete mastication, which is postponed for more leisurely performance.
• The food material, which is usually of a coarse nature, after being partly chewed enters the paunch or rumen, from which it is later regurgitated or returned to the mouth and rechewed in individual boluses during repose.
• This process of rechewing is known as rumination.

� � Function of Mastication��

• Physical breakdown increases the surface area of food, which improves the microbial digestion

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• Assist in appreciating the flavour of the food

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• Improves salivary and gastric activities

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• Initial digestion of carbohydrates is facilitated

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• Contributes to dilution and buffering of ruminoreticular fluid.

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Mechanism of mastication

• Reflex activity under the control of CNS. Mastication reflex or chewing reflex is the rhythmic movements of mandible.

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• Stimuli for masticatory reflex is the presence of food in the oral cavity. Receptors in tongue and oral mucosa which initiates mastication by the sense of food.

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• Sensory impulses are carried via trigeminal, facial, and glossopharyngeal nerves to brain stem.
• Efferent via trigeminal supplied to mastigatory muscles.In turn causes rhythmic movement of the mandible in relation to the maxilla. As results in shearing and crushing of food.

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• Main mastigatory muscles include temporalis with the assistance from masseter muscle for shearing and masseter with the assistance from pterygoid muscles for grinding.  

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• Mobile tongue of the ox has a groove across the upper surface a few inches back of its tip.

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• This groove is frequently the seat of injury caused by sharp spines, awns, etc., in forage eaten by cattle.

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• Injury is not a simple wound, and in most cases it results in the formation of a chronic ulcer with slight tendency to heal.

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• Although many types of the common wound-infection micro-organisms are found in the lesion, actinobacilli and actinomyces fungi are most often encountered and certainly cause the most damage.

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• Latter organisms are responsible for the so-called wooden tongue'' of cattle.

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• Because of this peculiar anatomy of the cow's tongue with its susceptibility to injury, care should be exercised to exclude from the feed as much as possible all sharp, spiny substances.

Rumination�Process of bringing back the cud from the rumen and reticulum to the mouth for further chewing�

Regurgitation

• The regurgitated cud consists of small particulate matter highly mixed with liquid and in advanced stage of fermentation.
• An antiperistalsis wave of oesophagus carries the cud to mouth.

Re- Mastication

• In the mouth, the liquid portion of the cud is squeezed and swallowed.
• The remaining solid mass is chewed with slow, regular chewing movements for about 40-seconds

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Rumination

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Re-insalivation

• During the process  of re -mastication saliva is added from parotid gland followed by re-swallowing

Re-deglutition

• It is the act of re-swallowing of the cud

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Note

• Time spent in rumination varies in different animals and with different rations.
• Average daily duration for rumination in cattle is 10 hours on hay diet.
• With low roughage diets or  finely ground roughage, total rumination time may be reduced to 3 hours/ day.
• Peak rumination occurs during afternoon and in the middle of the night.

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�Nervous control of Rumination�

• Rumination is a reflex act, but it can also be influenced by voluntary control.
• The receptors for rumination are in the reticular wall, cranial pillars of rumen and rumino-reticular fold.
• Vagus provides afferent nerve fibre to the rumination centre in the medulla.
• The efferent nerves are the motor nerves controlling muscles of larynx, oesophagus, and reticulum

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Deglutition (Swallowing)

• Deglutition is the act of passage of food from the mouth to the stomach through pharynx and oesophagus.
• Deglutition centre is situated in the medulla oblongata and inferior pons
• It is the motor activity involving the integrated movement of muscles of tongue, pharynx and oesophagus. (including the peristaltic movement)
• It is under direct neural control of brain.

Act of swallowing :

• takes place in three phases
• From mouth to pharynx (voluntary act)
• From pharynx into the oesophagus (reflex mechanism)
• From the oesophagus into the stomach (reflex mechanism)

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Swallowing (contd.)

• The quantity of food material that can be swallowed at one time is comparatively small in the horse while much larger bolus can be swallowed by the ox, whose deglutitive organs are of more ample proportions.
• Nevertheless, ruminants frequently choke on apples, beets, turnips, and other pieces of food that have not been chopped fine enough for ready swallowing with little chewing.
• There is no special or unusual factor involved in the swallowing process on the part of the pig, dog, cat, or fowl.

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