Structure and function of the salivary glands

During the Middle Ages, there was an interesting way to find out whether the person was guilty or not. He was offered to try dry rice. If a person could not swallow it, then he confessed guilty. Now it is difficult to believe, but at the heart of this method is the function of the salivary glands. This article will be devoted to our article.

Features of the structure of the human digestive system

The human digestive system is presented in two parts. This is a through "tube", which is called the digestive tract, and glands. The latter release special substances - enzymes. They accelerate chemical reactions, which contributes to the splitting of food in the tract. In the human body there are three types of such glands. The first include salivary. They are located in the oral cavity.

What are the functions of the salivary glands? They provide the primary processing of food. Although enzymes that contain saliva, can only break down complex carbohydrates into simpler ones.

Digestion in the oral cavity

The function of the salivary glands begins only after the mouth has analyzed the food for taste and temperature. This happens with the help of sensitive formations located in the mucosa, - the receptors.

Getting into the mouth, the food is wetted and machined with the help of teeth. In humans, they are differentiated. Depending on the structure, shape and functions distinguish incisors, canines, small and large molars. Here, too, is the chemical processing of food by saliva.

Structure and function of the salivary glands

There are three pairs of large salivary glands in the human: parotid, submandibular and sublingual. The first are located in the region of chewing muscles. In their thickness are the facial nerve, carotid artery and veins. In the sublingual region, the ducts of the submaxillary glands open. They are supplied with branches of the facial artery. Sublinguals are the smallest among the listed. They are in the area of ​​the eponymous fold. The small salivary glands include the palatine, lingual, labial, molar and buccal. The place of their localization is the mucous membrane of the oral cavity.

Functions of the salivary glands in digestion are determined primarily by the structure of the tissue to which they are formed, namely, the glandular epithelium. This tissue consists of small, tightly fitting cells. Thanks to this structure, a natural barrier is created between the body and the environment.

Saliva composition

Since the salivary glands perform the function of moisturizing and primary digestion of food, their secretion includes water and various enzymes. According to physical properties of saliva is a mucus-adhesive fluid. It is water that forms the basis, occupying more than 98% of the total composition. Enzymes, which include amylase, maltase and lysozyme, digest carbohydrates. A mucous consistency of saliva is given by a special substance - mucin. A unique property is the hormone parotin. It is also found in saliva and is able to strengthen tooth enamel.

Mineral and organic substances are constantly allocated to the oral cavity. The first group includes ions of sodium, potassium, calcium, silicon, magnesium, copper, as well as their chlorides, carbonates and phosphates. Organic components of saliva are proteins, enzymes, hormones and vitamins.

But the percentage of these elements is not constant. The composition of the elements of saliva can vary depending on the age, health, food composition, the presence of bad habits in humans. Thus, in smokers, the level of thiocyanate is much higher, since this substance neutralizes toxins of tobacco smoke. With age, the human body increases the content of magnesium and calcium in saliva.

Lysozyme

The second name of this substance is muramidase. It belongs to the group of hydrolytic enzymes. In addition to saliva, lysozyme is found in the lacrimal fluid, the gastrointestinal tract, the mucus of the nasopharynx, blood, liver, cartilaginous tissue. A lot of it in breast milk. Interesting is the fact that in human this substance is much more than in the cow. And over time, the amount of lysozyme in milk only increases.

Muramidase is capable of cleaving bacterial cell walls. This explains its disinfecting properties. The egg white also is rich in lysozyme. Among plant organisms this substance contains horseradish, turnip, cabbage and radish.

Amylase and maltase

The function of salivary gland enzymes is first of all secreting secrets for the cleavage of polysaccharides. In all there are about fifty. The leading ones are amylase and maltase.

Complex carbohydrates are also called sugars. But this does not mean that they are sweet to the taste. So, polysaccharides are rich in all food of plant origin. But with their splitting, there is a sweet taste. This phenomenon is due to the fact that monosaccharides, or simple sugars, are formed during this process. They also have sweetness.

Why does vegetable food digest so quickly? The fact is that the enzymes of saliva begin to break down the carbohydrates already in the oral cavity. But proteins and carbohydrates break down into monomers only in the stomach. Carbohydrates also get there already split and ready for absorption. Therefore, plant food significantly facilitates the work of the digestive system.

The properties of saliva enzymes are currently widely used in industry. For example, amylase, which contains yeast, is added to bakery products to improve their quality. And their presence in detergent powders determines the ability to rapidly break down starch.

Mucin

The function of the salivary glands is also in moistening the oral cavity and food particles. It is performed by mucin. This substance is also called slime. But in fact it is a complex protein, which includes, in addition to amino acids, carbohydrates. Mucin makes saliva viscous, because it has the ability to retain water. He covers the chewed chews of food, making them capable of further passage through the digestive tract. In addition, mucus also has disinfecting properties. It prevents the attachment of bacteria to the mucous membrane of the mouth, as well as their accumulation in its cavity.

How salivation is carried out

The saliva secretion process is reflexive. During food, food irritates the receptors of the tongue and mouth. In this case, nerve impulses are formed, which, through sensitive fibers, enter the medulla oblongata. There is a center of salivation. From it, impulses return to the glands. As a result, saliva is released. For a day a person produces it up to 1.5 liters. Salivation for food, which directly enters the oral cavity, is called unconditioned reflex.

But it can happen without food. For example, saliva can be released from a person at the sight of the food itself or its image, a sense of smell or even a thought about it. Just remember what the sour lemon looks like. This immediately causes a selection of saliva. But it will already be conditioned reflex.

It is worth saying that during sleep, saliva is practically not excreted. Its quantity decreases also during strong stressful situations, actions of anesthesia, at dehydration of an organism, nervous frustration, a climacterium, a renal failure and a diabetes.

There is also a chronic disease in which the amount of saliva is not enough. It is called xerostomia. Signs of this disease are dry mouth, excessive saliva viscosity, food taste insensitivity, painful sensations during swallowing and talking.

Swallowing food

The function of the salivary glands, which is carried out in the oral cavity, makes possible the further advancement of food. By the time when the food is swallowed, it is already mechanically crushed, moistened and partially split. Then the tongue pushes the food lump to the pharynx. How does he get into the esophagus? This is due to contractions of the muscles of the tongue and pharynx. At this time, the entrance to the respiratory tract is closed by the epiglottis cartilage. The walls of the esophagus are also contracted and the lump advances to the widest part of this system of organs - the stomach.

So, the functions of the human salivary glands are as follows:

- enzymatic - cleavage of complex carbohydrates into simple carbohydrates;

- protective - detoxification of microorganisms, healing of the oral mucosa, creation of a film on the enamel of the teeth, preventing the effect of organic acids on them;

- digestive - wetting and softening of food;

- hormonal - maintenance of mineralization of hard tissues of teeth;

- cleansing - washing out and removing from the oral cavity of foreign particles, food residues, microorganisms and toxins.