Hunger contractions, Thirst, and Vomition

a.      Prehension

The act of grasping food into mouth is called prehension.

• Different methods are applied by different species for prehension, e.g. Dog and Cat: use their tongue, Horse and Goats through lips.
• For drinking purpose also, different techniques are applied by animals. E.g. Cat, cannines lap the water with their tongue, some sucks and some lap.

b.     Mastication

• 1^st step of digestion
• Process of chewing ingested food and making it smaller when it mixed with saliva and making bolus ready to swallow
• Saliva play important role in mastication as it helps to soften the food and lubricate the food.
• Lower jaw movement with crushing part of teeth helps in chewing.
• Tongue and other Muscles like facial, elevator ,suprahyoidal helps in mastication
• Importance

1. helps to convert food particles into smaller particles
2. mixing of food
3. helps to increase surface area for digestion and enzymatic action
4. Help in forming bolus and make it easy for swallowing.

c. Deglutition

• The process of swallowing is called deglutition. It is a complex process

Stages:

I. Oral phase

• Tongue presses bolus into oropharynx
• Voluntary process
• Soft palate blocks entry to nasal cavity.

II. Pharyngeal phase

• When bolus reaches pharynx, several actions initiates.
• It involves movement of bolus from pharynx into esophagus.
• Vocal folds closed to prevent airway to lungs
• Larynx, pulled up with epiglottis to cover entry to trachea.
• Upper esophageal sphincter opens to allow passage to esophagus.

III. Esophageal phase

• Tongue presses backward and peristaltic contraction in pharynx occurs resulting in the movement of bolus into esophagus.

Note: When bolus is not delivered in ‘one pass’ secondary waves of peristalsis are initiated which will deliver bolus to stomach