Saliva is a watery secretion in the mouth (buccal cavity).
When there is a sigh of food, our mouth begins to water. This is because saliva is secreted at the sight of food.
Saliva has interesting functions in the mouth and digestive system.
Saliva in mouth
In the mouth, it has basic functions like
- Keeping the mouth moist
- Assisting in Digestion.
Saliva secretion: Saliva is secreted by salivary glands in the 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 the 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 cheekbone, and sublingual 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 and other pathogens
- Immunoglobulin A (IgA), an antibody that inhibits bacterial growth; and
- Electrolytes, including sodium, potassium, chloride,phosphate, and bicarbonate ions.
It has water as a major component. This helps keep our mouth moist all 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 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. We feel the food to be sweet as starch breaks down to glucose.
Hence, it is advised to chew the food well before swallowing it.
3. It moistens the food and makes a bolus by mucous.
This helps in the 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 dehydrated; it is 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 are open to air during speaking and eating.
Hence there are many microbes in the buccal environment. Saliva helps to kill them.
5. It keeps the mouth clean by evacuating any remained food debris from the mouth.
Hence we keep swallowing in normal hours, and any remains in the mouth get into the gut.
6. Saliva has immunoglobins IgA, a sort of antibody. 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 the 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.