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, he was found guilty. Now it’s hard to believe, but the salivary gland function is the basis of this method. This topic 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" called the digestive tract, and the gland. The latter secrete special substances - enzymes. They accelerate chemical reactions, which contributes to the breakdown 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 primary food processing. Although the enzymes that saliva contains are able to break down only complex carbohydrates into simpler ones.
Digestion in the oral cavity
The function of the salivary glands begins to be carried out only after the analysis of food for taste and temperature takes place in the oral cavity. This happens with the help of sensitive formations located in the mucous membrane - receptors.
Once in the oral cavity, the food is wetted and machined with the help of teeth. In humans, they are differentiated. Depending on the structure, shape and functions, there are incisors, fangs, small and large molars. Here, chemical processing of food by saliva occurs.
The structure and functions of the salivary glands
A person has three pairs of large salivary glands: parotid, submandibular and sublingual. The first are located in the area of the masticatory 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 with branches of the facial artery. Sublinguals are the smallest in size among those listed. They are located in the area of the same fold. Small salivary glands include the palatine, lingual, labial, molar, and buccal. 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 by which they are formed, namely, the glandular epithelium. This tissue consists of small, tight-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 breakdown of food, their secretion includes water and various enzymes. According to the 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, maltase and lysozyme, break down carbohydrates. Mucous consistency is given to saliva by a special substance - mucin. The hormone mumps has a unique property. It is also found in saliva and is able to strengthen tooth enamel.
Mineral and organic substances are constantly released into 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 may vary depending on age, state of health, food composition, the presence of bad habits in humans. So, in smokers, the level of rhodanide is much higher, since this substance neutralizes toxins of tobacco smoke. With age, a person 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 located in the lacrimal fluid, the membrane of the gastrointestinal tract, nasopharyngeal mucus, blood, liver, and cartilage. A lot of it is in breast milk. An interesting fact is that in human this substance is much more than in cow. Moreover, over 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, this substance contains horseradish, turnip, cabbage and radish.
Amylase and Maltase
The function of salivary gland enzymes is primarily the secretion of polysaccharides. In total there are about fifty. The leading ones are amylase and maltase.
Complex carbohydrates are also called sugars. But this does not mean that they taste sweet. So, polysaccharides are rich in all foods of plant origin. But when they are split, a sweet taste is felt. This phenomenon is due to the fact that during this process monosaccharides, or simple sugars, are formed. They have a sweetness.
Why is plant food 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, on the other hand, get there already split up and ready for absorption. Therefore, plant food greatly facilitates 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 washing powders determines the ability to quickly break down starch.
Mucin
The function of the salivary glands is also to moisten the oral cavity 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 chewed lumps 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 occurs
The process of salivation occurs reflexively. When 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 salivation center. From it, 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, which directly enters the oral cavity, is called unconditionally reflex.
But this can happen without food. For example, saliva can be released in a person at the sight of the food itself or its image, a sense of smell, or even thought about it. Just remember what sour lemon looks like. This will immediately cause salivation. But it will already be conditioned reflex.
It is worth saying that during sleep, saliva practically does not stand out. Its quantity also decreases during severe stressful situations, the effects of anesthesia, with dehydration, nervous disorders, menopause, renal failure and diabetes.
A chronic disease is also known 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 immunity, pain 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 the food is swallowed, it is already mechanically chopped, moistened and partially split. Next, the tongue pushes the food lump to the throat. How does he get into the esophagus? This is due to contractions in the muscles of the tongue and pharynx. At this time, the entrance to the airways is closed by the epiglottis cartilage. The walls of the esophagus also contract and the lump advances to 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 - the neutralization of microorganisms, the healing of the oral mucosa, the creation of a film on tooth enamel, which prevents exposure to organic acids on them;
- digestive - wetting and softening food;
- hormonal - providing mineralization of hard tissues of teeth;
- cleansing - washing and removing foreign particles, food debris, microorganisms and toxins from the oral cavity.