Respiratory organs of man. Human respiratory organs

Respiratory organs include: nasal cavity, pharynx. larynx, trachea, bronchi and lungs. The nasal cavity is divided by an osteochondral septum into two halves. Its inner surface is formed by three winding passages. Through them, air entering through the nostrils passes into the nasopharynx. Numerous glands located in the mucous membrane secrete mucus, which moisturizes the inhaled air. An extensive blood supply to the mucous membrane warms the air. On the moist surface of the mucous membrane, dust particles and microbes, which are neutralized by mucus and leukocytes, are retained in the inhaled air.

mucous membrane respiratory tract lined with ciliated epithelium, whose cells have on outside the surface of the thinnest outgrowths - cilia that can contract. The contraction of the cilia occurs rhythmically and is directed towards the exit from the nasal cavity. In this case, mucus and dust particles and microbes adhering to it are carried out of the nasal cavity. So the air passing through nasal cavity, warmed and cleaned of dust and some germs. This does not happen when air enters the body through oral cavity. That is why you should breathe through your nose and not through your mouth. Through the nasopharynx, air enters the larynx.

The larynx has the appearance of a funnel, the walls of which are formed by several cartilages. The entrance to the larynx during swallowing food is closed by the epiglottis, the thyroid cartilage, which can be easily felt from the outside. The larynx serves to conduct air from the pharynx to the trachea.

The trachea, or windpipe, is a tube about 10 cm long and 15–18 mm in diameter, the walls of which consist of cartilaginous half-rings interconnected by ligaments. The back wall is membranous, contains smooth muscle fibers, adjacent to the esophagus. The trachea divides into two main bronchi, which enter the right and left lungs and branch into them, forming the so-called bronchial tree.

On the terminal bronchial branches there are the smallest pulmonary vesicles - alveoli, 0.15–0.25 mm in diameter and 0.06–0.3 mm deep, filled with air. The walls of the alveoli are lined with a single-layer squamous epithelium, covered with a dense film of a substance that prevents them from falling off. The alveoli are permeated with a dense network blood vessels- capillaries. Gas exchange occurs through their walls.

The lungs are covered with a membrane - the pulmonary pleura, which passes into the parietal pleura, lining the inner wall chest cavity. The narrow space between the pulmonary and parietal pleura forms a pleural fissure filled with pleural fluid. Its role is to facilitate the sliding of the pleura during respiratory movements.

Respiration is the exchange of gases such as oxygen and carbon between internal environment person and the environment. Human breathing is a complexly regulated act of joint work of nerves and muscles. Their well-coordinated work ensures the implementation of inhalation - the supply of oxygen to the body, and exhalation - excretion carbon dioxide into the environment.

The respiratory apparatus has a complex structure and includes: organs of the human respiratory system, muscles responsible for the acts of inhalation and exhalation, nerves that regulate the entire process of air exchange, as well as blood vessels.

Vessels are of particular importance for the implementation of breathing. The blood enters through the veins lung tissue where gas exchange takes place: oxygen enters and carbon dioxide exits. The return of oxygenated blood is carried out through the arteries, which transport it to the organs. Without the process of tissue oxygenation, breathing would have no meaning.

Respiratory function is assessed by pulmonologists. Important indicators for this are:

1. Bronchial lumen width.
2. Breathing volume.
3. Inspiratory and expiratory reserve volumes.

A change in at least one of these indicators leads to a deterioration in well-being and is an important signal to additional diagnostics and treatment.

In addition, there are secondary functions that the breath performs. It:

1. Local regulation of the breathing process, due to which the vessels are adapted to ventilation.
2. Synthesis of various biologically active substances, carrying out the narrowing and expansion of blood vessels as needed.
3. Filtration, which is responsible for the resorption and decay of foreign particles, and even blood clots in small vessels.
4. Deposition of cells of the lymphatic and hematopoietic systems.

Stages of the breathing process

Thanks to nature, which invented such a unique structure and functions of the respiratory organs, it is possible to carry out such a process as air exchange. Physiologically, it has several stages, which, in turn, are regulated by the central nervous system, and only thanks to this they work like clockwork.

So, as a result of many years of research, scientists have identified the following stages, which collectively organize breathing. It:

1. External respiration - the delivery of air from the external environment to the alveoli. All organs of the human respiratory system take an active part in this.
2. Delivery of oxygen to organs and tissues by diffusion, as a result of this physical process tissue oxygenation occurs.
3. Respiration of cells and tissues. In other words, the oxidation of organic substances in cells with the release of energy and carbon dioxide. It is easy to understand that without oxygen, oxidation is impossible.

The value of breathing for a person

Knowing the structure and functions of the human respiratory system, it is difficult to overestimate the importance of such a process as breathing.

In addition, thanks to him, the exchange of gases between the internal and external environment human body. Respiratory system involved:

1. In thermoregulation, that is, it cools the body when elevated temperature air.
2. In the random selection function foreign substances such as dust, microorganisms and mineral salts, or ions.
3. In creating speech sounds, which is extremely important for social sphere person.
4. In the sense of smell.

Breathing is one of the most basic properties of any living organism. Its great importance is difficult to overestimate. About how important normal breathing is, a person thinks only when it suddenly becomes difficult, for example, when a cold has appeared. If without food and water a person is still able to live for some time, then without breathing - a matter of seconds. In one day, an adult makes more than 20,000 breaths and the same number of exhalations.

The structure of the human respiratory system - what it is, we will analyze in this article.

How does a person breathe?

This system is one of the most important human body. This is a whole set of processes that occur in a certain relationship and are aimed at ensuring that the body receives oxygen from environment and gave off carbon dioxide. What is respiration and how are the respiratory organs arranged?

The human respiratory organs are conditionally divided into airways and lungs.

The main role of the former is the unhindered delivery of air to the lungs. The respiratory tract of a person begins with the nose, but the process itself can also occur through the mouth if the nose is blocked. However nasal breathing preferable, because, passing through the nasal cavity, the air is purified, but if it enters through the mouth, it is not.

There are three main processes in respiration:

• external respiration;
• transport of gases with the bloodstream;
• internal (cellular) respiration;

When inhaling through the nose or mouth, the air first enters the throat. Together with the larynx and paranasal sinuses, these anatomical cavities belong to the upper respiratory tract.

The lower respiratory tract is the trachea, the bronchi connected to it, and the lungs.

Together they form a single functional system.

It is easier to visualize its structure using a diagram or a table.

During respiration, sugar molecules are broken down and carbon dioxide is released.

The process of respiration in the body

Gas exchange occurs due to their different concentrations in the alveoli and capillaries. This process is called diffusion. In the lungs, oxygen enters from the alveoli into the vessels, and carbon dioxide returns back. Both alveoli and capillaries consist of a single layer of epithelium, which allows gases to easily penetrate into them.

The transport of gas to the organs occurs as follows: first, oxygen enters the lungs through the airways. When air enters the blood vessels, it forms unstable compounds with hemoglobin in red blood cells, and with it moves to various bodies. Oxygen is easily detached and then enters the cells. In the same way, carbon dioxide combines with hemoglobin and is transported in the opposite direction.

When oxygen reaches the cells, it first penetrates into the intercellular space, and then directly into the cell.

The main purpose of respiration is the generation of energy in the cells.

The parietal pleura, pericardium and peritoneum are attached to the tendons of the diaphragm, which means that during breathing there is a temporary displacement of the organs of the chest and abdominal cavity.

When you inhale, the volume of the lungs increases when you exhale, respectively, decreases. At rest, a person uses only 5 percent of the total volume of the lungs.

Functions of the respiratory system

Its main purpose is to supply the body with oxygen and remove decay products. But the functions of the respiratory system may be different.

In the process of respiration, oxygen is constantly absorbed by the cells and at the same time they give off carbon dioxide. However, it should be noted that the organs of the respiratory system are also participants in other important functions organism, in particular, are directly involved in the formation of speech sounds, as well as smell. In addition, the respiratory organs are actively involved in the process of thermoregulation. The temperature of the air that a person inhales directly affects the temperature of his body. Exhaled gases lower body temperature.

Excretory processes also partially involve the organs of the respiratory system. Some water vapor is also released.

The structure of the respiratory organs, the respiratory organs also provide the body's defenses, because when air passes through the upper respiratory tract, it is partially cleansed.

On average, a person consumes about 300 ml of oxygen in one minute and releases 200 g of carbon dioxide. However, if it increases exercise stress, then oxygen consumption increases significantly. In one hour, a person is able to release from 5 to 8 liters of carbon dioxide into the external environment. Also, in the process of breathing, dust, ammonia and urea are removed from the body.

The respiratory organs are directly involved in the formation of human speech sounds.

Respiratory organs: description

All respiratory organs are interconnected.

Nose

This organ is not only an active participant in the breathing process. It is also the organ of smell. This is where the breathing process begins.

The nasal cavity is divided into sections. Their classification is as follows:

• lower section;
• average;
• upper;
• general.

The nose is divided into bone and cartilage sections. Nasal septum separates the right and left halves.

From the inside, the cavity is covered with ciliated epithelium. Its main purpose is to clean and warm the incoming air. The viscous slime which is here possesses bactericidal properties. Its quantity increases sharply with the appearance of various pathologies.

The nasal cavity contains a large number of small veins. When they are damaged, nosebleeds occur.

Larynx

The larynx is an extremely important component of the respiratory system, located between the pharynx and trachea. It is a cartilaginous formation. The cartilages of the larynx are:

1. Paired (arytenoid, corniculate, wedge-shaped, grain-shaped).
2. Unpaired (thyroid, cricoid and epiglottis).

In men, the junction of the plates of the thyroid cartilage strongly protrudes. They form the so-called "Adam's apple".

The joints of the body provide its mobility. The larynx has many various bundles. There is also a whole group of muscles that strain vocal cords. In the larynx are the vocal cords themselves, which are most directly involved in the formation of speech sounds.

The larynx is formed in such a way that the process of swallowing does not interfere with breathing. It is located at the level from the fourth to the seventh cervical vertebrae.

Trachea

The actual continuation of the larynx is the trachea. According to the location, respectively, the organs in the trachea are divided into the cervical and thoracic parts. The esophagus is adjacent to the trachea. Very close to it passes the neurovascular bundle. It includes carotid artery, nervus vagus and jugular vein.

The trachea branches into two sides. This point of separation is called a bifurcation. The posterior wall of the trachea is flattened. Here is located muscle. Its special location allows the trachea to be mobile when coughing. The trachea, like other respiratory organs, is covered with a special mucous membrane - ciliated epithelium.

Bronchi

The branching of the trachea leads to the next paired organ - the bronchi. The main bronchi in the region of the gate are divided into lobar. The right main bronchus is wider and shorter than the left.

At the end of the bronchioles are the alveoli. These are small passages, at the end of which there are special bags. They exchange oxygen and carbon dioxide with small blood vessels. The alveoli are lined from the inside with a special substance. They maintain their surface tension, preventing the alveoli from sticking together. Total alveoli in the lungs - approximately 700 million.

Lungs

Of course, all organs of the respiratory system are important, but it is the lungs that are considered the most significant. They directly exchange oxygen and carbon dioxide.

Organs are located in the chest cavity. Their surface is lined with a special membrane called the pleura.

The right lung is a couple of centimeters shorter than the left. The lungs themselves do not contain muscles.

The lungs are divided into two sections:

1. Top.
2. Base.

As well as three surfaces: diaphragmatic, costal and mediastinal. They are turned respectively to the diaphragm, ribs, mediastinum. The surfaces of the lung are separated by edges. The costal and mediastinal regions are separated by the anterior margin. The lower edge separates from the diaphragm area. Each lung is divided into lobes.

The right lung has three of them:

Upper;

Medium;

The left has only two: top and bottom. Between the lobes are interlobar surfaces. Both lungs have an oblique fissure. She shares shares in the body. The right lung additionally has a horizontal fissure separating the upper and middle lobes.

The base of the lung is expanded, and top part is narrowed. On the inner surface each part has small recesses called gates. Formations pass through them, creating the root of the lung. Here are the lymphatic and blood vessels, bronchi. In the right lung it is a bronchus, pulmonary vein, two pulmonary arteries. In the left - bronchus, pulmonary artery, two pulmonary veins.

In front of the left lung there is a small depression - the cardiac notch. From below, it is limited by a part called the tongue.

Protects lungs from external damage rib cage. The chest cavity is sealed, it is separated from the abdominal cavity.

Diseases associated with the lungs greatly affect general state human body.

Pleura

The lungs are covered with a special film - the pleura. It consists of two parts: outer and inner petal.

The pleural cavity always contains a small amount serous fluid providing wetting of the pleura petals.

The human respiratory system is designed in such a way that directly in pleural cavity there is negative air pressure. It is due to this fact, as well as the surface tension of the serous fluid, that the lungs are constantly in a straightened state, and they also accept respiratory movements. chest.

respiratory muscles

Respiratory muscles are divided into inspiratory (inhale) and expiratory (work during exhalation).

The main inspiratory muscles are:

1. Diaphragm.
2. External intercostal.
3. Intercartilaginous internal muscles.

There are also inspiratory accessory muscles (scalene, trapezius, pectoralis major and minor, etc.)

Intercostal, rectus, hypochondrium, transverse, external and internal oblique muscles of the abdomen are expiratory muscles.

Diaphragm

The diaphragm also plays an important role in the breathing process. This is a unique plate that separates two cavities: chest and abdomen. It belongs to the respiratory muscles. In the diaphragm itself, a tendon center and three more muscle areas are distinguished.

When contraction occurs, the diaphragm moves away from the chest wall. At this time, the volume of the chest cavity increases. Simultaneous contraction of this muscle and muscles abdominals causes the pressure inside the chest cavity to be less than the outside atmospheric pressure. At this point, air enters the lungs. Then, as a result of muscle relaxation, exhalation is carried out

The mucous membrane of the respiratory system

The respiratory organs are covered with a protective mucous membrane - ciliated epithelium. On the surface of the ciliated epithelium is great amount cilia constantly carrying out the same movement. Special cells located between them, together with the mucous glands, produce mucus that wets the cilia. Like duct tape, tiny particles of dust and dirt that have been inhaled by inhalation stick to it. They are transported to the pharynx and removed. In the same way, eliminate malicious viruses and bacteria.

It's natural and pretty effective mechanism self-purification. This structure of the shell and the ability to cleanse extends to all respiratory organs.

Factors affecting the state of the respiratory system

AT normal conditions the respiratory system works clearly and smoothly. Unfortunately, it can be easily damaged. Many factors can affect her condition:

1. Cold.
2. Excessively dry air generated in the room as a result of the operation of heating devices.
3. Allergy.
4. Smoking.

All this is extremely Negative influence on the state of the respiratory system. In this case, the movement of the cilia of the epithelium can significantly slow down, or even stop altogether.

Harmful microorganisms and dust are no longer removed, resulting in a risk of infection.

At first, this manifests itself in the form of a cold, and here the upper respiratory tract is primarily affected. There is a violation of ventilation in the nasal cavity, there is a feeling of nasal congestion, a general uncomfortable condition.

In the absence of correct and timely treatment in inflammatory process paranasal sinuses will be involved. In this case, sinusitis occurs. Then other signs of respiratory diseases appear.

Cough occurs due to excessive irritation of cough receptors in the nasopharynx. The infection is easily transferred from upper paths on the lower ones and the bronchi and lungs are already suffering. Doctors say in this case that the infection has "descended" below. This is fraught serious illnesses such as pneumonia, bronchitis, pleurisy. AT medical institutions strictly monitor the condition of equipment intended for anesthesia and respiratory procedures. This is done to avoid infection of patients. There are SanPiN (SanPiN 2.1.3.2630-10) that must be observed in hospitals.

As with any other system of the body, the respiratory system should be taken care of: treated in time if a problem occurs, and also avoided. negative influence environment and bad habits.

Human respiratory organs: a brief description

How good it is that you and I do not need to think in order to breathe or separately supply oxygen to each organ. Everything has long been calculated and developed, it happens by itself. And a person simply quite unconsciously inhales and then exhales about once every four seconds. At first glance, everything is elementary. However, the respiratory organs in the body constitute a complex system, where each element performs extremely important functions.

And, perhaps, it can be called the most important for a person. The elements of this system are the upper (oral and nasal cavities, as well as the pharynx) and lower (larynx, trachea, and bronchi) respiratory tract and, of course, the lungs. This also includes blood vessels and some muscles. It is customary to refer to the respiratory system also a set of nerve endings that promote gas exchange.

Lungs

Considering all the human respiratory organs, this one can rightfully be called the main one. The lungs are located in the chest on either side of the heart. In them, the very process of gas exchange between a person and the environment takes place directly. Thanks to a large number alveoli - small balls at the ends of the branches of the bronchi - oxygen is supplied to the entire body. Life-giving gas from here is delivered by blood to all tissues and organs. It is because of the great importance of the lungs that their diseases are extremely dangerous.

Let's start with the breath itself. Most often, we take air from the environment through the nose. However, this can also be done with the help of the mouth. Air enters the nasal (oral) cavity. In the first case - much better. This is due to the fact that in the nasal cavity the air is cleared of dust particles and various microbes. This is due to the presence of special mucus and small villi - cilia. In addition, the air is warm here. After the nose (mouth), it falls into the pharynx, which connects just these cavities. From there - into the larynx. This is where the human voice box is located. Air moves from the larynx into the trachea. It is a flexible tube up to fifteen centimeters long. The trachea connects the human larynx and the bronchi. From this flexible tube, air enters just into them. The bronchi are the so-called bifurcation of the trachea and further branching. And this “tree” ends with the alveoli, which have already been mentioned.

They are so small that there are up to seven hundred million of them in both lungs. Each alveolus is covered with a dense network of tiny capillaries, which provide the process of gas exchange.

Animal respiratory organs: features

In other representatives of the fauna, the gas exchange system may (more or less strongly) differ. So, in fish, the main respiratory organs are gills. In worms and amphibians, this is often the entire surface of the body. The main respiratory organs of insects are the tracheae; in reptiles, the lung sacs. The gas exchange system becomes more complex depending on the size of the animal. To a lesser extent, depending on the habitat and "life style". But one thing is constant: not a single representative of the animal world on our planet can live without oxygen.

Breath - a set of physiological processes constantly occurring in a living organism, as a result of which it absorbs oxygen from the environment and releases carbon dioxide and water. Respiration provides gas exchange in the body, which is a necessary link in the metabolism. Respiration is based on oxidation processes. organic matter- carbohydrates, fats and proteins, as a result of which energy is released, which ensures the vital activity of the body.

Inhaled air through airways (nasal cavity, larynx, trachea, bronchi) reaches the pulmonary vesicles (alveoli), through the walls of which, richly braided with blood capillaries, gas exchange occurs between air and blood.

In humans (and vertebrates), the breathing process consists of three interrelated stages:

• external respiration,
• transport of gases by the blood and
• tissue respiration.

Essence external respiration consists in the exchange of gases between the external environment and blood, occurring in special respiratory organs- in the lungs. Oxygen enters the blood from the external environment, and carbon dioxide is released from the blood (only 1-2% of the total gas exchange is provided by the surface of the body, that is, through the skin).
The change of air in the lungs is achieved by rhythmic respiratory movements of the chest, carried out by special muscles, due to which an alternate increase and decrease in the volume of the chest cavity is obtained. In humans, the chest cavity during inhalation increases in three directions: anterior-posterior and lateral - due to the raising and rotation of the ribs, and vertically - due to the lowering of the chest-abdominal barrier (diaphragms).

Depending on the direction in which the chest volume mainly increases, there are:

• chest,
• abdominal and
• mixed types breathing.

When breathing, the lungs passively follow the chest walls, expanding when inhaling and contracting when exhaling.
The total surface area of ​​the lung alveoli in humans is on average 90 m 2 . A person (adult) at rest does. 16-18 respiratory cycles (i.e., inhalations and exhalations) in 1 min.
With each breath, about 500 ml of air enters the lungs, which is called respiratory. With a maximum breath, a person can inhale about 1500 more ml of the so-called. additional air . If, after a calm exhalation, an additional intensified exhalation is made, then another 1500 ml of the so-called. reserve air .
Breathing, supplementary and reserve air add up lung capacity.
However, even after the most intense exhalation, 1000-1500 ml of residual air still remains in the lungs.

Minute breathing volume or ventilation of the lungs, varies depending on the body's need for oxygen and in an adult at rest is 5-9 liters of air per 1 minute.
During physical work When the body's need for oxygen sharply increases, ventilation of the lungs increases to 60-80 liters per minute, and in trained athletes even up to 120 liters per minute. With aging, the body's metabolism decreases, and size also decreases; lung ventilation. With an increase in body temperature, the respiratory rate increases slightly and in some diseases reaches 30-40 per 1 minute; while the depth of breathing decreases.

Respiration is controlled by the respiratory center medulla oblongata central nervous system. In humans, in addition, the cerebral cortex plays an important role in the regulation of breathing.

Gasooben occurs in the alveoli of the lungs. To get into the alveoli of the lungs, the air during breathing passes through the so-called respiratory tract: it first penetrates into nasal cavity, further into throat, which is a common path for air and for food entering it from the oral cavity: then the air moves through the purely respiratory system - larynx, respiratory throat, bronchi. Bronchi, gradually branching, reaches microscopic bronchioles, from which air enters pulmonary alveoli.

tissue respiration - a complex physiological process, manifested in the consumption of oxygen by cells and tissues of the body and in the formation of carbon dioxide by them. Tissue respiration is based on redox processes accompanied by the release of energy. Due to this energy, all vital processes are carried out - continuous renewal, growth and development of tissues, secretion of glands, muscle contraction, etc.

NOSE AND NOSE CAVITY - the initial part of the respiratory tract and the organ of smell.
Nose built from paired nasal bones and nasal cartilages, giving it an external shape.
nasal cavity It is located in the center of the facial skeleton and represents a bone canal lined with mucous membrane, which runs from the holes (nostrils) to the choanae, connecting it with the nasopharynx.
The nasal septum divides the nasal cavity into right and left halves.
Characteristic of the nasal cavity are adnexal sinuses - cavities in adjacent bones (maxillary, frontal, ethmoid), which communicate with the nasal cavity through holes and channels.

The mucous membrane lining the nasal canal consists of ciliated epithelium; its hairs have constant oscillatory movements in the direction of the entrance to the nose, which blocks access to the respiratory tract for small coal, dust, and other particles inhaled with air. The air entering the nasal cavity is warmed in it due to the abundance of blood vessels in the mucous membrane of the nasal cavity and warmed air paranasal sinuses. This protects the respiratory tract from direct exposure to low external temperatures. Forced breathing through the mouth (eg, deviated septum, nasal polyps) raises the possibility of respiratory infections.

PHARYNX - part of the digestive breathing tube located between the nasal and oral cavities at the top and the larynx and esophagus at the bottom.
The pharynx is a tube, the basis of which is muscle layer. The pharynx is lined with a mucous membrane, and on the outside it is covered with a connective tissue layer. Throat lies in front cervical spine down from the skull to the 6th cervical vertebra.
Most upper section pharynx - nasopharynx - lies behind the nasal cavity, which opens into it with choanae; this is the way for air inhaled through the nose to enter the pharynx.

During the act of swallowing, the airways are isolated: the soft palate (palatine curtain) rises and, pressing against the back wall of the pharynx, separates the nasopharynx from the middle part of the pharynx. Special muscles pull the pharynx up and forward; due to this, the larynx is also pulled up, and the root of the tongue presses down on the epiglottis, which thus closes the entrance to the larynx, preventing food from entering the respiratory tract.

LARYNX - Start windpipe (trachea), including a voice box. The larynx is located on the neck.
The structure of the larynx is similar to the device of the so-called reed wind instruments. musical instruments: there is a narrowed place in the larynx - the glottis, into which the air pushed out of the lungs vibrates the vocal cords, which play the same role as the tongue plays in the instrument.

The larynx is located at the level of the 3rd-6th cervical vertebrae, bordering behind the esophagus and communicating with the pharynx through an opening called the entrance to the larynx. Below the larynx passes into the windpipe.
The base of the larynx forms an annular-shaped cricoid cartilage, which connects below with trachea. On the cricoid cartilage, movably connecting with it by a joint, the largest cartilage of the larynx is located - the thyroid cartilage, consisting of two plates, which, connecting in front at an angle, form a protrusion on the neck that is clearly visible in men - Adam's apple.

On the cricoid cartilage, also connected to it by joints, there are symmetrically located 2 arytenoid cartilages, each bearing a small santorini cartilage at its apex. Between each of them and the inner corner of the thyroid cartilage are stretched 2 true vocal cords that limit the glottis.
The length of the vocal cords in men is 20-24mm, in women - 18-20mm. Short ligaments give a higher voice than long ligaments.
When breathing, the vocal cords diverge, and the glottis takes the form of a triangle with its apex forward.

RESPIRATORY THROAT (Trachea) - the airway following the larynx through which air passes to the lungs.
The windpipe begins at the level of the 6th cervical vertebra and is a tube consisting of 18-20 incomplete cartilaginous rings, closed behind by smooth muscle fibers, as a result of which back wall its soft and flattened. This allows the esophagus behind it to expand as it passes. food bolus when swallowing. Having passed into the chest cavity, the windpipe is divided at the level of the 4th thoracic vertebra into 2 bronchi going to the right and left lungs.

BRONCHI The branches of the windpipe (trachea) through which air enters and leaves the lungs during breathing.
The trachea in the chest cavity is divided into right and left primary bronchi, which enter the right and left lungs, respectively: successively dividing into smaller and smaller secondary bronchi. They form the bronchial tree, which forms the dense base of the lung. The diameter of the primary bronchi is 1.5-2 cm.
The smallest bronchi bronchioles, have microscopic dimensions and represent the final sections of the airways, at the ends of which the respiratory tissue lung, educated alveoli.

The walls of the bronchi are formed by cartilaginous rings and smooth muscles. Cartilaginous rings cause the obstinacy of the bronchi, their non-falling and unhindered movement of air during breathing. The inner surface of the bronchi (as well as other parts of the respiratory tract) is lined with a mucous membrane with ciliated epithelium: epithelial cells are provided with cilia.

LUNGS represent paired organ. They are enclosed in the chest and are located on the sides of the heart.
Each lung has the shape of a cone, the wide base of which is turned down to the thoracic obstruction. (aperture), the outer surface - to the ribs that form the outer wall of the chest, the inner surface covers the heart shirt with the heart enclosed in it. The apex of the lung protrudes above the clavicle. The average size of an adult lung: the height of the right lung is 17.5 cm, the left one is 20 cm, the width at the base of the right lung is 10 cm, the left one is 7 cm. The lungs have a fluffy texture, because they are filled with air. From the inner surface, the bronchus, vessels and nerves enter the gates of the lung.

The bronchus conducts air into the lungs through the nasal (oral) cavity, into the larynx and trachea. In the lungs, the bronchus gradually divides into smaller secondary, tertiary, etc. bronchi, making up, as it were, the cartilaginous skeleton of the lung; the final branching of the bronchi is the conducting bronchiole; she aims at the alveolar passages, the walls of which are dotted with pulmonary vesicles - alveoli.

The pulmonary arteries carry carbon dioxide from the heart to the lungs. venous blood. Pulmonary arteries divide parallel to the bronchi and eventually break up into capillaries, covering the alveoli with their network. Back from the alveoli, the capillaries gradually gather into veins that leave the lungs as pulmonary veins, which enter the left side of the heart and carry oxygenated arterial blood.

Gas exchange between the external environment and the body occurs in the alveoli.
Air containing oxygen enters the cavity of the alveoli, and blood flows to the walls of the alveoli. When air enters the alveoli, they expand and, conversely, collapse when air leaves the lung.
Thanks to thinnest wall the alveoli here easily undergoes gas exchange - the entry of oxygen into the blood from the inhaled air and the release of carbon dioxide from the blood into it; blood is purified, it becomes arterial and is carried further through the heart to the tissues and organs of the body, in which it gives off oxygen and takes in carbon dioxide.

Each lung is covered with a sheath - pleura, passing from the lungs to the chest wall; so lung way enclosed in a closed pleural sac formed by the parietal pleura. Between the pulmonary and parietal pleura there is a narrow gap containing a small amount of fluid. With respiratory movements of the chest, the pleural cavity (together with the chest) expands, and the descending diaphragm lengthens its upper-lower size. Due to the fact that the gap between the sheets of the pleura is airless, the expansion of the chest causes negative pressure in the pleural cavity, stretches the lung tissue, which is thus sucked in through the airways (mouth - trachea - bronchi) atmospheric air entering the alveoli.

Expansion of the chest during inhalation is active and is performed with the help of respiratory muscles (intercostal, scalariform, abdominal); its fall during exhalation occurs passively and with the assistance of the elastic forces of the tissue of the lung itself. The pleura provides sliding of the lung in the chest cavity during respiratory movements.