1. How Saliva Dissolves Sweetness So the Tongue Can Taste It
Taste is delivered in a "dissolved state." When you lick a candy, you immediately know it is sweet. According to an explanation by the Health and Longevity Net, the flavor components of food first dissolve into saliva. The dissolved substance then stimulates receptors in the taste buds on the tongue, sending signals to the brain so you can sense the taste [1].
The basic tastes that can be distinguished are saltiness, sourness, sweetness, bitterness, and umami [1]. Taste buds are not only on the tongue. A dictionary notes there are about 5,000 on the tongue and about 2,500 elsewhere, such as on the soft palate, pharynx, and larynx [2]. Because numbers vary by source, it is best to think of them as "several thousand."
It is estimated that the cells that sense taste are replaced with new cells about every 10 days [3]. The water that delivers taste is saliva. How much of this saliva is produced each day?
2. How Much Saliva Our Salivary Glands Make Each Day
Saliva comes mainly from three large salivary glands: the parotid, submandibular, and sublingual glands. The daily amount is about 1 to 1.5 liters, and the secretion volume changes with age [4].
There are two types of saliva. One is "resting saliva," which flows constantly without special stimulation. The other is "reflex saliva," which comes out due to stimuli like smell, taste, chewing, or temperature [4]. Chewing gum or chewing food well is said to stimulate the salivary glands.
The fact that saliva flows even when you are not eating connects to the later topics of teeth and pronunciation. First, let us look at what the act of chewing itself is useful for.
Safety Note: Read this amount as a guideline for adults; children’s amounts may not be the same.
3. The Three Jobs of Chewing Food
An encyclopedia lists three meanings for chewing (mastication) [5]. First, soluble components in food dissolve, stimulating taste and increasing appetite and digestive tract movement. Second, food is crushed finely, increasing the area where digestive juices work. Third, the food mass is wrapped in saliva’s mucus to make it easier to swallow.
Chewing is not just crushing; it includes mixing and forming food with saliva in the mouth. The taste story in section 1 and the reflex saliva in section 2 happen simultaneously within the chewing motion.
The food formed in the mouth is next sent to the throat. Here, a problem arises because food and air pass through the same entrance.
4. How the Throat Closes the Airway When We Swallow
Swallowing (deglutition) is divided into three stages. First is the oral phase, where you consciously send chewed food to the pharynx. Next is the pharyngeal phase, where the swallowing reflex, which you cannot stop yourself, sends food to the entrance of the esophagus. Finally, in the esophageal phase, peristalsis moves food to the stomach [6].
During the pharyngeal phase, the pharynx moves forward and upward. As part of this reflex, the epiglottis falls like a lid over the entrance of the larynx to close the airway, and the entrance to the esophagus opens. The center of this reflex is in the medulla oblongata [6].
The mouth also passes air. However, materials from the Japan Health Insurance Association state that nasal breathing is the most appropriate method for the body. Mouth breathing is explained as being prone to causing irregular tooth alignment, cavities, and periodontal disease [8]. It is also pointed out that if the mouth becomes dry from breathing through it, the amount of saliva may decrease.
Safety Note: Only the oral phase is a conscious movement; from there, it proceeds automatically. This is a feature of swallowing.
5. How Saliva Helps Repair Softened Tooth Surfaces After Eating
After eating, if the mouth becomes acidic, minerals dissolve from the tooth surface, and the enamel softens. At this time, saliva helps restore the hardness by replenishing minerals on the tooth surface over about an hour. This action is called remineralization [7].
Saliva has other protective jobs. A document from Katsushika Ward lists antibacterial action, self-cleaning to wash away food debris, buffering to return the acidic mouth to neutral, remineralization, digestion by enzymes, and protecting mucous membranes with mucin [4].
If the mouth becomes dry, the functions of saliva may weaken. Mucin in saliva is also said to cover mucous membranes, making pronunciation, vocalization, and chewing smooth. Let us move to the mouth’s other big job: speaking.
6. How Tiny Tongue-Tip Movements Make the Sounds "Hi," "Shi," and "Su"
An explanation page from the National Museum of Ethnology states that the differences between the sounds "Hi," "Shi," and "Su" are born from subtle differences in the movement of the tongue tip. It says that both consonants and vowels are expressed by slight differences in mouth shape and tongue position [9].
The functions of the mouth include eating, speaking, breathing, and making facial expressions [8]. Within the job of speaking, the function of producing correct sounds is generally said to be completed around age 5 to 6. If the muscle strength of the lips or tongue is insufficient, it can affect pronunciation. However, this is a guideline, and not everyone completes it at the same time.
Saliva, tongue, teeth, lips, and throat each have separate roles but work together connected within one mouth.
7. How to Feel Your Mouth and Throat Working When You Swallow
What you can do today: Gently touch your throat with your fingers and swallow. Since the pharynx is said to move forward and upward [6], you might feel the movement with your fingers. Do not use force; just touch it gently.
Another activity is to say "Hi," "Shi," and "Su" slowly in a small voice and feel how the tongue and mouth shape change each time. You can understand with your body that sounds are made by differences in tongue and mouth shape [9].
If you want to know more, the explanation on the National Museum of Ethnology’s website, Loquens, is written in Japanese and details how pronunciation is born. The Katsushika Ward document "The Power of Saliva" lists the functions of saliva [4]. Investigating why the number of taste buds differs by source is also a path to learning.