Saliva is a watery secretion of buccal cavity (mouth).
It seems like something which waters when there is sight of food. But it has many interesting functions in mouth.
It is a has some important components besides water.
It is the one which keeps our mouth moist all the day and helps in lubrication to speak and spell easily.
Saliva helps in proper chewing of the food and making a bolus.
This is done by articulating the food gulp in between the teeth and tongue.
It also helps in partial digestion of food, swallowing and also keeping the mouth clean.
Saliva secretion: Saliva is secreted by salivary glands in mouth.
These glands are located in various regions in and around the buccal cavity. The intrinsic glands are small and numerous in number dispersed in numerous spots in mouth. The extrinsic glands are bigger and in pairs. Their secretion is higher than the intrinsic glands.
They are parotid glands situated juts near the ear and empty secretion in mouth. The sub-mandibular gland is near the cheek bone and sub-lingual glands are below the tongue.
The secretion happens as signal from the brain when there is sight or scent of food.
Saliva is watery secretion with a stable pH of around 7. It also has important constituents like
- Salivary amylase, an enzyme that begins starch digestion in the mouth.
- Lingual lipase, an enzyme that is activated by stomach acid and digests fat after the food is swallowed
- Mucus, which binds and lubricates the food mass and aids in swallowing.
- Lysozyme, an enzyme that kills bacteria
- Immunoglobulin A (IgA), an antibody that inhibits bacterial growth; and
- Electrolytes, including sodium, potassium, chloride,phosphate, and bicarbonate ions.
Saliva has many functions though it seems to be a simple secretion. These include
1. Saliva helps in recognition of taste. On a dry tongue taste recognition is difficult to recognize the taste. With salivary moisture, the taste buds can sense the taste from the dissolved substance.
2. Saliva partially digests carbohydrates due to salivary amylase enzyme. Hence we feel the food to be sweet as starch breaks down to glucose.
3. It moistens the food and makes a bolus by mucous. This helps in easy swallowing of the chewed food. Or else it can be painful to swallow dry. You might have felt such instances in daily life when food was very dry, it very difficult to swallow.
4. It kills bacteria due to an enzyme lysozyme present in it. There are food particles in the mouth and also is open to air during speaking and eating. Hence there are many microbes in the buccal environment. Saliva helps to kill them.
5. It keep the mouth clean by evacuating any remained food debris from mouth. Hence we keep swallowing in normal hours and any remains in mouth get into gut.
6. Saliva has immunoglobins IgA a sort of antibodies. These bind to microbes and prevent the pathogens from entering into deeper tissues and destroys them.
7. It helps in creating a sense of thirst when body is deprived of water. When body water levels are low, the saliva secretion stops making one feel mouth dry and desire to drink water.