When breathing through the nose, air passes with greater resistance than when breathing through the mouth, therefore, when breathing through the nose, the work of the respiratory muscles increases and breathing becomes deeper. Atmospheric air, passing through the nose, is warmed, moistened, and purified. Warming occurs due to the heat given off by the blood flowing through a well-developed system of blood vessels in the nasal mucosa. The nasal passages have a complex tortuous structure, which increases the area of the mucous membrane with which atmospheric air comes into contact.
In the nose, the inhaled air is purified, and dust particles larger than 5-6 microns in diameter are captured in the nasal cavity, and smaller ones penetrate into the underlying sections. The nasal cavity secretes 0.5-1 liters of mucus per day, which moves in the posterior two-thirds of the nasal cavity at a speed of 8-10 mm/min, and in the anterior third - 1-2 mm/min. Every 10 minutes a new layer of mucus passes through, which contains bactericidal substances (lysozyme, secretory immunoglobulin A).
The oral cavity is of greatest importance for respiration in lower animals (amphibians, fish). In humans, breathing through the mouth occurs during intense conversation, fast walking, running, or other intense physical activity, when the need for air is great; for diseases of the nose and nasopharynx.
Breathing through the mouth in children in the first six months of life is almost impossible, since the large tongue pushes the epiglottis backward.
Gas exchange in the lungs.
The gas mixture in the alveoli involved in gas exchange is usually called alveolar air or alveolar gas mixture. The content of oxygen and carbon dioxide in the alveoli depends, first of all, on the level of alveolar ventilation and the intensity of gas exchange.
The remainder of the alveolar gas mixture consists of nitrogen and a very small amount of inert gases.
Atmospheric air contains:
20.9 rev. % oxygen,
0.03 rev. % carbon dioxide,
79.1 rev. % nitrogen.
Exhaled air contains:
16 rev. % oxygen,
4.5 rev. % carbon dioxide,
79.5 rev. % nitrogen.
The composition of alveolar air during normal breathing remains constant, since with each inhalation only 1/7 of the alveolar air is renewed. In addition, gas exchange in the lungs occurs continuously, during inhalation and exhalation, which helps to equalize the composition of the alveolar mixture.
The partial pressure of gases in the alveoli is: 100 mm Hg. for O 2 and 40 mm Hg. for CO 2. The partial pressures of oxygen and carbon dioxide in the alveoli depend on the ratio of alveolar ventilation to lung perfusion (capillary blood flow). In a healthy person at rest, this ratio is 0.9-1.0. Under pathological conditions, this balance can undergo significant shifts. As this ratio increases, the partial pressure of oxygen in the alveoli increases, and the partial pressure of carbon dioxide decreases, and vice versa.
Normal ventilation - the partial pressure of carbon dioxide in the alveoli is maintained within 40 mm Hg.
Hyperventilation is increased ventilation that exceeds the metabolic needs of the body. The partial pressure of carbon dioxide is less than 40 mm Hg.
Hypoventilation is reduced ventilation compared to the metabolic needs of the body. The partial pressure of CO 2 is more than 40 mm Hg.
Increased ventilation is any increase in alveolar ventilation compared to the resting level, regardless of the partial pressure of gases in the alveoli (for example: during muscular work).
Eipnea is normal ventilation at rest, accompanied by a subjective feeling of comfort.
Hyperpnea is an increase in the depth of breathing, regardless of whether the respiratory rate is increased or decreased.
Tachypnea is an increase in respiratory rate.
Bradypnea is a decrease in respiratory rate.
Apnea is a cessation of breathing caused by a lack of stimulation of the respiratory center (for example: with hypocapnia).
Dyspnea is an unpleasant subjective feeling of shortness of breath or difficulty breathing (shortness of breath).
Orthopnea is severe shortness of breath associated with stagnation of blood in the pulmonary capillaries as a result of heart failure. In a horizontal position, this condition is aggravated and therefore it is difficult for such patients to lie.
Asphyxia is cessation or depression of breathing, mainly associated with paralysis of the respiratory center. Gas exchange is sharply disrupted: hypoxia and hypercapnia are observed.
Diffusion of gases in the lungs.
The partial pressure of oxygen in the alveoli (100 mmHg) is significantly higher than the oxygen tension in the venous blood entering the capillaries of the lungs (40 mmHg). The partial pressure gradient of carbon dioxide is directed in the opposite direction (46 mm Hg at the beginning of the pulmonary capillaries and 40 mm Hg in the alveoli). These pressure gradients are the driving force for the diffusion of oxygen and carbon dioxide, i.e. gas exchange in the lungs.
According to Fick's law, diffuse flux is directly proportional to the concentration gradient. The diffusion coefficient for CO 2 is 20-25 times greater than for oxygen. All other things being equal, carbon dioxide diffuses through a certain layer of the medium 20-25 times faster than oxygen. That is why the exchange of CO 2 in the lungs occurs quite completely, despite the small gradient of the partial pressure of this gas.
As each red blood cell passes through the pulmonary capillaries, the time during which diffusion is possible (contact time) is relatively short (about 0.3 s). However, this time is quite enough for the tension of respiratory gases in the blood and their partial pressure in the alveoli to become almost equal.
The diffusion capacity of the lungs, like alveolar ventilation, should be considered in relation to the perfusion (blood supply) of the lungs.
In order to create a proper performance about otolaryngology, as one of the links in a multifaceted medical science, it is necessary first of all to get acquainted with some physiological and pathological data that determine the importance of the upper respiratory tract in the general economy of the body.
Nose and throat occupy in a person's life a special place and, as we will see, deservedly bear the name “guardian of health.”
Feeling sense of smell protects us from inhaling air containing any harmful impurities, and also, to a certain extent, warns us against eating poor quality food.
Along with this, the top Airways play an important role in the process of gas exchange. In a normal nose, the air needed for breathing undergoes a number of very significant changes. In contact with the richly vascularized nasal mucosa, cold atmospheric air is significantly warmed. In addition, passing through the winding nasal passages, it is freed from all impurities, be it particles of organic or inorganic dust, or various types of living microorganisms. This phenomenon is explained not only by the purely mechanical action of the moist nasal mucosa, but also by the undoubtedly proven bactericidal property of nasal mucus.
Finally, in the nasal cavity, dry atmospheric air is saturated with the necessary amount of moisture, the source of which is the secretion of the nasal mucosa and lacrimal glands.
Thus, we see that the nose is indeed a protective organ for the respiratory tract.
From here it is clear that all sorts of things a change in the normal patency of the nose, whether it be a narrowing of its lumen or, conversely, an excessive expansion of it, inevitably entails a disorder of the protective function, which is reflected in a number of shortcomings of a local and general nature.
However, this relatively The modest role of the protector of the respiratory tract does not exhaust the function of the nose as a guardian of health. In order to get a proper idea of its significance in the life of a healthy and sick organism, it is necessary to become familiar with some features of the physiology of respiration.
For proper implementation gas exchange First of all, it is necessary that the inhaled air, when entering the upper respiratory tract, encounter a certain resistance, because only under such conditions is sufficiently intense work of the respiratory muscles achieved. The act of inhalation is carried out mainly due to the contraction of the diaphragm and intercostal muscles, which, causing expansion of the chest, reduces the negative pressure present in it. The latter, in turn, is the driving force that causes passive expansion of the lung tissue.
Exhalation carried out under normal conditions due to the fact that, due to their inherent elasticity, they subside as soon as the pressure in the chest returns to its original position.
Necessary Remember that in the process of breathing, not all the air filling the lungs is renewed. A certain part of it, the so-called residual air, can under no circumstances be exhaled from the lungs. The removal of this part of the air is made possible only because at the moment of inhalation, negative pressure is created in the chest. At this time, the residual air spreads in both lungs before fresh atmospheric air has time to enter through the narrow lumen of the nose, with which it mixes.
At breathing through the mouth, this process is carried out to an insufficient extent due to the fact that the air when inhaled does not meet the necessary resistance (Verkhovsky).
The degree of resistance that various parts of the respiratory tract provide to the air stream is determined by the following digital data:
Resistance: respiratory tract as a whole - 100%, upper respiratory tract - 54%, nose - 47.3%, pharynx - 4.76%, glottis - 1.2%, trachea - 0.74%, broncho-lobular system - 46%.
Thus, the nasal cavity offers the greatest resistance to the air stream.
From here It's clear, how exceptionally important breathing through the nose is for the process of gas exchange, because due to the difficulty that the upper segment of the respiratory tract has in the entry of air into the lungs, especially favorable conditions are created for the formation of negative pressure in the chest. The importance of this factor is confirmed not only by numerous clinical observations, but also by corresponding experimental studies, which have established that turning off the nose from the act of breathing, i.e. breathing through the mouth, primarily leads to an increase in the amount of residual air.
Thus, we see that only breathing through the nose should be considered a normal physiological type of breathing.
So breathing through mouth, which replaces the nasal one in all cases of nasal obstruction, should be classified as pathology.
And indeed, mouth breathing causes a number of deviations from the norm, both local and general. In addition to the direct harm to the body already noted above from the loss of the protective function of the nose, various kinds of phenomena are observed here, caused by insufficient respiratory excursions of the lungs. First of all, as is known, breathing through the mouth has a harmful effect on the condition of the pulmonary apices, in which the phenomena of atelectasis are often observed.
Selective effect of insufficient breathing on a specific area lung(in this case, the apex) is explained by the fact that the upper part of the chest takes part in the respiratory act only during deep breathing. When breathing is at rest or weakened, only the lower part of the chest functions predominantly. The consequence of this is the collapse of the pulmonary apices, which, if this condition persists for a long time, leads to atelectasis. It is possible that chronic inflammation of the pulmonary parenchyma, which develops in mouth breathers due to the irritating effect of dust contained in the air, also plays a certain role in this process. There is no doubt that such changes in the pulmonary apices occur quite often in persons with poor nasal breathing and, perhaps, are interpreted as healed foci of tuberculosis origin.
In the process of evolution, nasal breathing arose and developed in humans. Why do you need to breathe through your nose?
Nasal breathing
Breathing through the nose has several benefits. These include the following:
- Warming the cold inhaled air. If you breathe through your mouth, the likelihood of catching a cold in the autumn-winter period increases.
- Disinfection with nasal mucus. The secretions contain antibodies and enzymes that successfully fight viruses.
- Additional immune protection. The pharyngeal tonsil is located in the nasopharynx, the lymphoid tissue of which acts as an immune barrier.
When a person breathes through the mouth, air immediately enters the throat. If it is cold, a reflex cough may develop, sometimes even laryngospasm. This is typical for young children and people with calcium metabolism disorders.
The first barrier that microorganisms encounter when breathing through the mouth is the tonsils. Saliva also has antimicrobial properties, but its capabilities are limited. When breathing through the nose, the degree of protection is more pronounced, and the likelihood of developing the disease when infected with viruses is lower.
In addition, during nasal breathing, the air is cleared of dust and other particles that settle on the villi and nasal walls. It is for these reasons that you need to breathe correctly, through your nose.
Pathology of nasal breathing
In some situations, nasal breathing is disrupted. This occurs in the following diseases:
- Deviation of the nasal septum.
- Adenoids of the second or third degree.
- Allergic rhinitis with severe swelling of the mucous membrane.
- Nasal polyps.
Nasal breathing may persist partially or disappear completely. The patient has to inhale air through his mouth. In this case, the following manifestations will be noted:
- Frequent pharyngitis and tonsillitis, otitis.
- Headache.
- Impaired sense of smell.
- Snore.
In children, breathing through the mouth with adenoids leads to the formation of a characteristic “adenoid” face. This feature also prevents them from developing normally and playing sports.
In adults, impaired nasal breathing leads to limited physical activity and health problems.
Answers to school textbooks
Pulmonary respiration ensures gas exchange between air and blood. Tissue respiration produces gas exchange between blood and tissue cells. There is cellular respiration, which ensures the use of oxygen by cells for the oxidation of organic substances, releasing energy used for their vital functions.
2. What are the advantages of nasal breathing over mouth breathing?
When breathing through the nose, the air passing through the nasal cavity warms up, is cleared of dust and is partially disinfected, which does not happen when breathing through the mouth.
3. How do protective barriers work to prevent infection from entering the lungs?
The path of air to the lungs begins from the nasal cavity. The ciliated epithelium, which lines the inner surface of the nasal cavity, secretes mucus, which moisturizes the incoming air and traps dust. Mucus contains substances that have a negative effect on microorganisms. On the upper wall of the nasal cavity there are many phagocytes and lymphocytes, as well as antibodies. The cilia of the ciliated epithelium expel mucus from the nasal cavity.
The tonsils, located at the entrance to the larynx, also contain a huge number of lymphocytes and phagocytes that destroy microorganisms.
4. Where are the receptors that perceive odors located?
The olfactory cells, which sense odors, are located at the top of the back of the nasal cavity.
5. What belongs to the upper and what to the lower respiratory tract of a person?
The upper respiratory tract includes the nasal and oral cavities, nasopharynx, and pharynx. To the lower respiratory tract - larynx, trachea, bronchi.
6. How do sinusitis and sinusitis manifest? What words do the names of these diseases come from?
The manifestations of these diseases are identical: nasal breathing is impaired, copious discharge of mucus (pus) from the nasal cavity occurs, the temperature may rise, and performance decreases. The name of the disease, sinusitis, comes from the Latin “sinus maxillary” (maxillary sinus), and frontitis comes from the Latin “sinus frontalis” (frontal sinus).
7. What signs suggest the growth of adenoids in a child?
In children, the bite and dentition are formed incorrectly, the lower jaw grows, protrudes forward, but acquires a “Gothic” shape. With all this, the nasal septum is deformed, as a result of which nasal breathing is difficult.
8. What are the symptoms of diphtheria? Why is it unsafe for the body?
The main symptoms of diphtheria include:
Gradual increase in temperature, lethargy, decreased appetite;
A grayish-white coating appears on the tonsils;
The neck swells due to inflammation of the lymph glands;
A wet cough at the beginning of the disease, gradually turning into a rough, barking cough, and then into a silent one;
Breathing is noisy, difficult to inhale;
Increasing respiratory failure, pale skin, cyanosis of the nasolabial triangle;
Sharp anxiety, cool sweat;
Loss of consciousness and severe pallor of the skin precede the fatal ending.
Diphtheria toxin, which is a waste product of the diphtheria bacillus, affects the conduction system of the heart and the heart muscle. With all this, a serious and dangerous heart disease appears - myocarditis.
9. What is introduced into the body during treatment with anti-diphtheria serum, and what is introduced during vaccination against this disease?
Anti-diphtheria serum contains specific antibodies obtained from horses. During vaccination, a small amount of antigen is injected.
Between the respiratory and circulatory systems?
4. What are the functions of the nasal cavity, larynx, trachea and main bronchi?
5. How does voice formation occur and speech sounds are formed?
6. What is sinusitis, frontal sinusitis, tonsillitis?
The meaning of breathing.
A person can do without food for several weeks, without water for several days, without air for only a few minutes. Nutrients are stored in the body, like water, but the supply of fresh air is limited by volume lungs. That is why its continuous updating is necessary. Thanks to the ventilation of the lungs, they maintain a more or less constant gas composition, which is necessary for the entry of oxygen into the blood and the removal of carbon dioxide, other gaseous decay products, and water vapor from the blood.
From previous chapters we know what happens to tissues when insufficient oxygen is supplied to them: tissue function is impaired because the breakdown and oxidation of organic substances stops, energy ceases to be released, and cells, deprived of energy supply, die.
Respiration is the exchange of gases between cells and the environment. In humans, gas exchange consists of four stages:
1) exchange of gases between the air and the lungs;
2) exchange of gases between the lungs and blood;
3) transportation of gases by blood;
4) gas exchange in tissues.
The respiratory system performs only the first part of gas exchange. The rest is done by the circulatory system. There is a deep relationship between the respiratory and circulatory systems. There are pulmonary respiration, which provides gas exchange between air and blood, and tissue respiration, which provides gas exchange between blood and tissue cells.
In addition to ensuring gas exchange, the respiratory organs perform two more important functions: functions: participate in thermoregulation and voice formation. When you breathe, water evaporates from the surface of the lungs, which cools the blood and the entire body. In addition, the lungs create air currents that vibrate the vocal cords of the larynx.
The structure and function of the respiratory organs in humans (Fig. 59). The organs that supply air to the alveoli of the lungs are called the respiratory tract. Upper respiratory tract: nasal and oral cavities, nasopharynx, pharynx. Lower respiratory tract: larynx, trachea, bronchi.
The bronchi branch repeatedly, forming the bronchial tree. Through them, air reaches the alveoli, where gas exchange occurs. Each of the lungs occupies a hermetically sealed part of the chest cavity. Between them is a heart. The lungs are covered by a membrane called the pulmonary pleura.
The nasal cavity consists of several winding passages, divided by a solid septum into left and right parts (Fig. 60). The inner surface of the nasal cavity is lined with ciliated epithelium. It secretes mucus, which moisturizes the incoming air and traps dust. Mucus contains substances that have a detrimental effect on microorganisms. The cilia of the ciliated epithelium expel mucus from the nasal cavity.
A dense network of blood vessels runs through the walls of the nasal cavity. Hot arterial blood moves in them towards the inhaled cold air and warms it.
On the upper wall of the nasal cavity there are many phagocytes and lymphocytes, as well as antibodies (see § 18).
At the back of the nasal cavity are olfactory cells that sense odors. The appearance of a pungent odor leads to a reflexive holding of breath.
Thus, the upper respiratory tract performs important functions: warming, humidifying and purifying the air, as well as protecting the body from harmful influences through the air.
From the nasal cavity, air enters the nasopharynx, and then into the pharynx, with which the oral cavity communicates.
Therefore, a person can breathe through both the nose and mouth. When breathing through the nose, the air in the nasal cavity warms up, is cleared of dust and is partially disinfected, which does not happen when breathing through the mouth. But it is easier to breathe through the mouth, and therefore tired people instinctively breathe through the mouth.
From the pharynx, air enters the larynx.
The entrance to the trachea begins through the larynx (Fig. 61). It is a wide tube, narrowed in the middle and reminiscent of an hourglass. The larynx consists of cartilage. It is covered in front and on the sides by the thyroid cartilage. In men, it protrudes slightly forward, forming the Adam's apple.
The narrow part of the larynx contains the vocal cords. There are two pairs of them, but only one, the lower pair, is involved in vocal production. Ligaments can come closer together and stretch, that is, change the shape of the gap that forms between them. When a person breathes calmly, the ligaments are separated. When breathing deeply, they move apart even further; when singing and speaking, they close, leaving only a narrow gap, the edges of which vibrate. They are the source of sound vibrations, on which the pitch of the voice depends. In men, the ligaments are longer and thicker, their sound vibrations are lower in frequency, and therefore the male voice is lower. Children and women have thinner and shorter ligaments, and therefore their voice is higher.
The sounds generated in the larynx are amplified by resonators - the paranasal sinuses - cavities located in the facial bones filled with air (Fig. 62). Under the influence of the air stream, the walls of these cavities vibrate slightly, as a result of which the sound intensifies and acquires additional shades. They determine the timbre of the voice.
Sounds made by the vocal cords are not speech. Articulate speech sounds are formed in the oral and nasal cavities depending on the position of the tongue, lips, jaws and the distribution of sound flows. The work of the listed organs when pronouncing articulate sounds is called articulation.
Correct articulation is formed especially easily between the ages of one and five years, when the child masters his native language. When communicating with young children, there is no need to lisp or copy their incorrect pronunciation, as this leads to the consolidation of mistakes and impaired speech development.
Trachea and main bronchi.
From the larynx, air enters the trachea. This is a fairly wide tube, which consists of cartilaginous half-rings with a soft side facing the esophagus, which is adjacent to the trachea at the back (see Fig. 59, A).
The inner wall of the trachea is covered with ciliated epithelium. The vibrations of its eyelashes remove dust particles from the lungs into the throat. This is called the process of self-cleaning of the lungs. Below, the trachea branches into two main bronchi - right and left. The bronchi have cartilaginous rings that protect them from collapse during inhalation. In small bronchi, small cartilaginous plates remain instead of rings, and in the smallest bronchi, bronchioles, they are absent.
Infectious and chronic diseases of the respiratory tract.
Paranasal sinuses. Some skull bones have air cavities - sinuses. In the frontal bone there is a frontal sinus, in the maxillary there is a maxillary sinus (Fig. 62).
Flu, sore throat, acute respiratory infection (acute respiratory disease) can cause inflammation of the mucous membrane of the paranasal sinuses. The maxillary sinuses are most often affected. Their inflammation is sinusitis. Often there is inflammation of the frontal sinus - frontal sinusitis. With sinusitis and frontal sinusitis, there is a violation of nasal breathing, the release of mucus from the nasal cavity, often purulent. Sometimes the temperature rises. A person's performance decreases. Treatment with an otolaryngologist, a specialist who treats people with diseases of the ear, nose and throat, is required.
Tonsils.
From the nasal cavity, air enters the nasopharynx, then the pharynx and larynx. The tonsils are located behind the soft palate and at the entrance to the esophagus and larynx. They are composed of lymphoid tissue similar to that found in lymph nodes. The tonsils contain many lymphocytes and phagocytes that trap and destroy microbes, but sometimes they themselves become inflamed, swollen and painful. A chronic disease occurs - tonsillitis.
Adenoids are tumor-like growths of lymphoid tissue at the exit from the nasal cavity into the nasopharynx. Sometimes (Fig. 63) enlarged adenoids block the passage of air and nasal breathing becomes difficult.
Tonsillitis and enlarged adenoids must be treated in a timely manner: surgically or conservatively (i.e., without surgery).
Diphtheria is an infectious disease spread by airborne droplets. Diphtheria most often affects children, but adults also suffer from it. It starts out like a regular sore throat. Body temperature rises, grayish-white plaques appear on the tonsils. The neck swells due to inflammation of the lymph glands (Fig. 64, B).
The causative agent of diphtheria is the diphtheria bacillus. The product of its vital activity is a toxic substance - diphtheria toxin, which affects the conduction system of the heart and the heart muscle. A serious and dangerous heart disease occurs - myocarditis.
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