During the Middle Ages, there was an interesting way to find out whether a person is guilty or not. He was offered to try dry rice. If a person could not swallow it, then he was found guilty. Now it's hard to believe, but this method is based on the function of the salivary glands. Our article will be devoted to this topic.
Features of the structure of the human digestive system
The human digestive system is represented by two parts. This is a through "tube", which is called the digestive tract, and glands. The latter secrete special substances - enzymes. They speed up chemical reactions, which contributes to the breakdown of food in the tract. There are three types of these glands in the human body. The first are salivary. They are located in the mouth.
What are the functions of the salivary glands? They provide primary food processing. Although the enzymes that saliva contains can only break down complex carbohydrates into simpler ones.
Digestion in the mouth
The function of the salivary glands begins to be carried out onlyafter the food is analyzed in the oral cavity for taste and temperature. This happens with the help of sensitive formations located in the mucous membrane - receptors.
Once in the mouth, food is wetted and mechanically processed by the teeth. In humans, they are differentiated. Depending on the structure, shape and function, incisors, canines, small and large molars are distinguished. The chemical processing of food with saliva also takes place here.
Structure and functions of the salivary glands
Man has three pairs of major salivary glands: parotid, submandibular and sublingual. The first are located in the region of chewing muscles. In their thickness pass the facial nerve, carotid artery and veins. In the sublingual region, the ducts of the submandibular glands open. They are supplied by branches of the facial artery. The hyoids are the smallest in size among those listed. They are located in the region of the fold of the same name. Minor salivary glands include the palatine, lingual, labial, molar, and buccal glands. The place of their localization is the mucous membrane of the oral cavity.
The functions of the salivary glands in digestion are determined primarily by the structure of the tissue they are formed from, namely, the glandular epithelium. This tissue is made up of small, tightly packed cells. Thanks to this structure, a natural barrier is created between the body and the environment.
Composition of saliva
Because the salivary glands function as a moisturizing and primarydigestion of food, their secretion includes water and various enzymes. According to its physical properties, saliva is a mucous-adhesive liquid. It is water that forms its basis, occupying more than 98% of the total composition. Enzymes, which include amylase, m altase and lysozyme, break down carbohydrates. The mucous consistency of saliva is given by a special substance - mucin. The hormone parotin has a unique property. It is also found in saliva and can strengthen tooth enamel.
Mineral and organic substances are constantly released into the oral cavity. The first group includes sodium, potassium, calcium, silicon, magnesium, copper ions, as well as their chlorides, carbonates and phosphates. The organic constituents of saliva are proteins, enzymes, hormones and vitamins.
But the percentage of these elements is not constant. The composition of saliva elements can vary depending on the age, state of he alth, food composition, and the presence of bad habits in a person. For example, smokers have a much higher level of thiocyanate, since this substance neutralizes the toxins of tobacco smoke. As a person ages, the content of magnesium and calcium in saliva increases.
Lysozyme
The second name of this substance is muramidase. It belongs to the group of hydrolysis enzymes. In addition to saliva, lysozyme is found in the lacrimal fluid, the lining of the gastrointestinal tract, nasopharyngeal mucus, blood, liver, and cartilage tissue. A lot of it is in breast milk. An interesting fact is that in the human this substance is much more than in the cow. Andover time, the amount of lysozyme in milk only increases.
Muramidase is able to break down the cell walls of bacteria. This explains its disinfecting properties. Egg white is also rich in lysozyme. Among plant organisms, horseradish, turnip, cabbage and radish contain this substance.
Amylase and m altase
The function of the enzymes of the salivary glands is, first of all, the release of secrets for the breakdown of polysaccharides. There are about fifty of them in total. The leading ones are amylase and m altase.
Complex carbohydrates are also called sugars. But this does not mean that they are sweet in taste. So, all foods of plant origin are rich in polysaccharides. But when they are split, a sweet taste is felt. This phenomenon is due to the fact that monosaccharides, or simple sugars, are formed during this process. They have sweetness.
Why are plant foods digested so quickly? The fact is that saliva enzymes begin to break down carbohydrates already in the oral cavity. But proteins and carbohydrates break down into monomers only in the stomach. Carbohydrates get there already split and ready for absorption. Therefore, plant foods greatly facilitate the work of the digestive system.
The properties of saliva enzymes are now widely used in industry. For example, amylase, which yeast contains, is added to bakery products to improve their quality. And their presence in washing powders determines the ability to quickly break down starch.
Mucine
The function of the salivary glands is also to moisten the mouth and food particles. It is performed by mucin. This substance is also called mucus. But in fact, it is a complex protein, which, in addition to amino acids, includes carbohydrates. Mucin makes saliva viscous because it has the ability to retain water. It envelops the chewed lumps of food, making them capable of further passage through the digestive tract. In addition, mucus also has disinfecting properties. It prevents bacteria from attaching to the mucous membrane of the mouth, as well as their accumulation in its cavity.
How salivation occurs
The process of salivation occurs reflexively. While eating, food irritates the receptors of the tongue and oral cavity. In this case, nerve impulses are formed, which, through sensitive fibers, enter the medulla oblongata. There is a center of salivation. From it, the impulses return to the glands. As a result, saliva is released. For a day, a person produces up to 1.5 liters of it. Salivation for food that directly enters the oral cavity is called unconditioned reflex.
But it can happen without the availability of food. For example, saliva can be released from a person when they see the food itself or its image, smell it, or even think about it. Just remember what a sour lemon looks like. This will immediately cause saliva to flow. But it will already be conditioned reflex.
It is worth saying that during sleep, saliva is practically not released. Decreases hernumber and during severe stressful situations, the effects of anesthesia, dehydration, nervous disorders, menopause, kidney failure and diabetes.
There is also a chronic disease in which the amount of saliva is not enough. It's called xerostomia. Signs of this disease are dry mouth, excessive viscosity of saliva, insensitivity to the taste of food, pain during swallowing and talking.
Swallowing food
The function of the salivary glands, which is carried out in the oral cavity, makes it possible to further move food. By the time the food is swallowed, it is already mechanically crushed, moistened and partially split. Next, the tongue pushes the food bolus to the throat. How does it get into the esophagus? This happens due to contractions of the muscles of the tongue and pharynx. At this time, the entrance to the respiratory tract is closed by the epiglottic cartilage. At the same time, the walls of the esophagus also contract and the lump moves towards the most expanded part of this organ system - the stomach.
So, the functions of the human salivary glands are as follows:
- enzymatic - splitting complex carbohydrates into simple ones;
- protective - neutralization of microorganisms, healing of the oral mucosa, creation of a film on tooth enamel, preventing exposure to organic acids;
- digestive - wetting and softening food;
- hormonal - ensuring the mineralization of hard dental tissues;
- cleansing - washing out and removing from the oral cavityforeign particles, food debris, microorganisms and toxins.
