What are barrier functions. An organ that performs a barrier function in the human body

Man has been studying his physical body throughout his history. And although science has made many amazing discoveries, and the functions of each organ have long been known, the human body never ceases to amaze us with extraordinary endurance and miracles of adaptability. Often a person does not suspect what possibilities are contained in his own body, and only emergencies and the threat of death can mobilize powerful forces hidden for a time.

The next book in the series tells about the most amazing mysteries of the human body. The book is published in the author's edition.

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When talking about the unique ability of the human body to resist numerous pathogenic bacteria and viruses, it is sometimes compared to an impregnable fortress with several defensive lines.

The skin and mucous membranes are the first to meet uninvited guests. This is a rather serious obstacle for many microorganisms. For example, the skin has a special system, thanks to which it is freed from bacteria and microbes that have fallen on its surface. The sebaceous and sweat glands are engaged in this work. They secrete lactic and fatty acids, which lower the pH (pH) to 5.5. As a result, the surface of the skin becomes acidic, and such an environment for the life of most microbes is absolutely unsuitable.

Protect our body from disease-causing agents and epithelial cells that line the gastrointestinal tract, respiratory tract, channels of the excretory system. For example, in the mucous membrane of the gastrointestinal tract there are substances that kill harmful microbial flora. In the stomach, dangerous "aliens" are affected by gastric juice containing hydrochloric acid.

In addition, various microorganisms are constantly present outside and inside our body, collectively called microflora. So, in the intestine there is a huge amount of bacteria that, constantly living there, not only do not harm our body, but, on the contrary, most often help it to function normally, killing hostile microscopic aliens.

The skin also has its "permanent inhabitants" engaged in the defense of our body. For example, they quite successfully resist such a dangerous adversary as the causative agent of anthrax. And the pneumococci that live in the upper respiratory tract effectively fight influenza viruses. In women, the normal microflora of the vagina is represented by six types of bacteria that form an environment in which other microorganisms cannot live.

The central organ of the immune system is the thymus, or spectacle gland

And saliva and tears contain special protein substances, which are also deadly for many microbes.

But often microbes and viruses still break through the outer protective barriers. And then the body's immune system takes over. Its main task is to recognize and remove all foreign biological objects from the body: microbes, viruses, fungi, and even your own cells and tissues if they change and become dangerous.

The immune system includes organs, tissues and cells of various structures and functions. But, despite this, all its components are a single whole, and the main defenders have a common pedigree.

The roots of the immune system are in an unusual place: inside the bones. Yes, yes, it is from here that it originates, developing from the bone marrow.

It is laid in the embryo at the end of the second month of development, and by the time the child is born, it fills all the cavities of the bones. And the numerous blood vessels penetrating it give the bone marrow a red color. The bone marrow performs a very important and responsible function in the body - it produces cellular elements of the blood: erythrocytes, leukocytes, platelets.

But the bone marrow does not retain its blood-red color for long. Almost immediately after birth (in the first 6 months), the first fat cells begin to appear in the bone marrow. And already by the age of 20-25, all the bone marrow cavities of the diaphyses of long tubular bones are actually completely filled with yellow bone marrow.

The red bone marrow is, in fact, the central organ of the human immune system. In adults, it is concentrated in the cellular structures of the scapula, pelvic bones and other flat bones. In addition, it is located inside the spongy bones - the sternum, vertebrae, etc., as well as in the end sections of the tubular bones. The total weight of the bone marrow reaches 1.5 kilograms.

The red brain appears from myeloid tissue, which contains small, 8–10 micron in diameter, hematopoietic stem cells, which, in fact, are the progenitors of all blood cells. Then these elements are delivered by the blood stream to the organs of the immune system, in which they further specialize.

Having arrived at the place, the stem cell continues its development, which can go in one of two directions.

The first of these is the transformation into B-lymphocytes. This name is associated with a special organ in birds in which these cells reach a state of maturity. It is called the bag of Fabricius and consists of a section of lymphatic tissue in the wall of the cloaca. A bag in Latin "bursa". According to the first letter of this word, lymphocytes got their name.

Anatomists and physiologists tried to find a similar organ in humans. But they never found it. For this reason, it has been suggested that the analogue of the "bursa" is located in the bone marrow. Or perhaps it is represented by lymph nodes located in the ileum or in the vermiform appendix - the appendix.

As for the structure and role of B-lymphocytes in the body, these are small cells with a diameter of 8.5 microns, with a nucleus located inside. They are the main participants in the immunological reactions of a special, so-called humoral type, the main duty of which is the timely and effective protection of the body from various microorganisms.

Stem cells, once in the organs of the immune system, can also differentiate into another type of defender cells - T-lymphocytes. But in order to turn into a T-lymphocyte, the stem cell needs to get into another central organ of the immune system - the thymus, which is often called the thymus gland. This is a soft formation of light yellow color, which is located in the chest cavity, behind the upper part of the sternum. The thymus consists of two parts, different in shape and size, tightly adjacent to one another.

In the human body, it appears in the first month of development of the human embryo. In a newborn baby, the weight of the thymus reaches 12 grams. Every year, its mass gradually increases, and in a mature person, the thymus weighs approximately 35-40 grams.

And suddenly, at the peak of development, strange metamorphoses begin to occur in the thymus: it begins to lose weight, and its tissue is filled with fat cells. Moreover, these processes occur quite quickly, and by the age of 25, the thymus already weighs about 25 grams. In old age, its weight is even less - about 15 grams. And in the elderly, it generally turns into a dwarf weighing about 6 grams, that is, two times lighter than that of a baby.

The thymus consists of the following structural elements. Outside, it is covered with a connective tissue capsule. The strands extending deep from it - septa - divide the pitchfork of the spectacle gland into small lobules. Under the capsule is the outer cortical layer with a huge number of dividing lymphocytes. Two more layers are located deeper: the cortical substance of the thymus proper and the medulla.

As small lymphocytes reach maturity, they move from the cortex to the medulla. Some of the lymphocytes in this area of ​​the thymus die. At the same time, others continue their development and at various stages, up to fully mature T-cells, leave the thymus into the circulatory and lymphatic systems, through which they circulate throughout the body.

In addition to lymphocytes, other cellular elements of the immune system are also present in the fork of the spectacle gland in small quantities: cells that eat foreign elements - macrophages and neutrophils, involved in the body's allergic reactions - eosinophils, and highly specialized immune cells called mast, which are involved in adaptive immunity.

So, the thymus is the central structure of the immune system, engaged in the production of T-lymphocytes, the name of which, as you might guess, comes from the first letter of the word "thymus". The main function of T-lymphocytes is to "fight" with foreign elements and control the production of antibodies against pathogens.

It should be borne in mind that the number of lymphocytes in the fork of the spectacle gland directly depends on the time of day. Indeed, there are more of them in the thymus during the day and at night, and less in the evening and in the morning. This is due to the fact that in the morning and evening they move into the bloodstream.

Curious is the fact that the cells of the thymus are completely renewed within only 4-6 days.

barrier function

the ability of the human and animal organism through special physiological mechanisms, the so-called. barriers, protect its internal environment (blood, lymph, tissue fluid) from external influences and maintain the relative constancy of its composition, chemical, physical and biological properties (see Homeostasis). Conditionally distinguish between external barriers (skin, mucous membranes, respiratory, excretory and digestive apparatus) and internal - Histo-hematic barriers , located between the blood and tissue (extracellular) fluid of organs and tissues. Among the external barriers, the liver barrier is especially important, neutralizing toxic compounds formed in the intestines and entering the blood from it. B. f. determines to a large extent the vital activity of organs and tissues, their sensitivity to bacteria, poisons, toxins, metabolic products, foreign substances, drugs. The plasticity of external and internal barriers, their adaptability to changing environmental conditions are important for the normal existence of the organism, protecting it from diseases, intoxications, etc. The following have been studied in the most detail: the blood-brain barrier (between the blood and the brain), the hemato-ophthalmic barrier (between the blood and tissues of the eye), the placental barrier (between the mother's body and the fetus), etc. A large role in the development of the theory of B. f. the works of Soviet scientists (L. S. Stern, A. A. Bogomolets, B. N. Mogilnitsky, A. I. Smirnova-Zamkova, and others) played a role.

Lit.: Stern L. S., Direct nutrient medium of organs and tissues, M., 1960; Development and regulation of histohematic barriers. Sat., ed. L. S. Stern. Moscow, 1967.

G. N. Kassil.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what the "Barrier function" is in other dictionaries:

BARRIER FUNCTION- BARRIER FUNCTION. Barriers are adaptations that protect the organism or its individual organs from the environment and thus make it, to a certain extent, independent of the changes taking place in it. There are two kinds... ... Big Medical Encyclopedia

barrier function- an auxiliary function used in solving some problems of mathematical programming. It tends to minus infinity (∞) when approaching the boundary of the range of permissible values ​​from the inside. When moving from a task ... ... Economic and Mathematical Dictionary

barrier function- An auxiliary function used in solving some problems of mathematical programming. It tends to minus infinity (??) when approaching the border of the range of permissible values ​​from the inside. In the transition from the maximization problem to the problem ... ... Technical Translator's Handbook

F. tissues and organs, which consists in protecting the body or its individual parts from the effects of environmental changes and in maintaining the relative constancy of the composition, physicochemical and biological properties of the internal environment of the body ... Big Medical Dictionary

I Infant A child under the age of one year. Allocate the neonatal period, lasting 4 weeks. after birth (see Newborn (Newborn)) and infancy (from 4 weeks to 1 year). In infancy, the child grows and ... ... Medical Encyclopedia

I The liver (hepar) is an unpaired organ of the abdominal cavity, the largest gland in the human body, which performs a variety of functions. In the liver there is a neutralization of toxic substances entering it with blood from the gastrointestinal tract; in her... Medical Encyclopedia

This article is about the organ of the human reproductive system. For other uses of the term vagina, see Vagina (disambiguation). "Vagina" redirects here; see also other meanings. Vagina ... Wikipedia

1-1 is slowly injected into the cavity of the ventricle of the heart.5 ml suspension of vaseline oil in saline. The suspension, before drawing into the syringe, is thoroughly shaken to an emulsion state.

Under a microscope, the appearance and movement of fat emboli through the vessels of the mesentery are observed, which in some places completely clog the vessels (Fig. S). Draw a picture of the embolism of the vessels of the mesentery.

Then, slowly injected into the cavity of the ventricle of the heart 0,2- 0,3 ml of ethanol solution. AT flow For 20-30 minutes, the gradual formation in the vessels of a large number of small aggregates similar to granules (granular blood flow), characteristic of the amorphous type of sludge, is observed. The blood flow gradually slows down, a pendulum movement of blood develops, stasis.

Draw a picture of sludge in the vessels of the mesentery. The development of sludge can also be observed on a preparation of the tongue of a frog.

The frog immobilized by destruction of the spinal cord is fixed on the dissecting

plank on the back, open the chest and abdominal cavity and prepare the preparation of the mesentery.

Under a microscope (small magnification), blood circulation in the vessels of the mesentery of the frog is observed. Then, 0.5-1 ml 10% high molecular weight dextran solution. During 30 minutes are observed for changes in blood circulation in the microvessels of the mesentery, narrowing of axial blood flow, the appearance of rather large aggregates first in venular vessels, then in arterioles, slowing of blood flow, pendulum-like movement of blood with aggregates suspended in it, development of sludge.

Draw a picture of dextran sludge in the vessels of the mesentery.

Topic 3. Barrier functions of the body and their violations