THE MOUTH
Chewing (mastication)
reduces the particle size of
food and increases its
exposure to saliva.
This process lubricates food
for swallowing and also aids
in carbohydrate digestion by
the enzyme salivary amylase.
The distribution of foodstuffs
around the mouth during
chewing stimulates the taste
receptors.
Although chewing is a voluntary act,
it is largely coordinated by the reflex centers in the brainstem.
Saliva secreted from each of several salivary glands is mixed together in the mouth
to produce a composite juice that is mildly alkaline. Eating decreases pH of
saliva.The volume of saliva produced is approximately 1.5 L per day.
The three major functions of saliva are lubrication, protection, and digestion:
1. Lubrication
includes moistening the mouth as well as lubricating
the food to aid swallowing. Saliva facilitates movements of the mouth
and tongue for speech and helps to dissolve chemicals within food for
its presentation to the taste receptors.
2. Protection
relates to reducing the adverse effects of oral bacteria
(e.g., dental caries). The alkalinity of fresh saliva neutralizes acid
produced by oral bacteria; the flow of saliva across the teeth also
helps to wash away bacteria. Saliva contains additional substances
that reduce bacterial growth.
- Lysozyme attacks bacterial cell walls.
- Lactoferrin chelates iron, which is needed by many bacteria for replication.
- Immunoglobin A (IgA)-binding protein is required for the immunologic
activity of IgA.
3. The digestive function of saliva is to begin the breakdown of
carbohydrates and fats via the enzymes α-аmylase and Lingual lipase.
Stimuli caused salivation are
integrated by the salivary nuclei
in the pons, and salivation is
determined by the resulting
parasympathetic tone.
Acinar secretion is stimulated by
the release of acetylcholine,
which acts via the muscarinic
receptors.
The factors changed the saliva :
The green colored factors stimulate salivation, the red colored factors inhibit it.
The green colored factors stimulate salivation, the red colored factors inhibit it.
