The upper respiratory tract is a link in a multicomponent respiratory system that absorbs oxygen from the environment, transfers it to tissues, oxidizes reactions in tissues, transfers carbon dioxide to the lungs and removes it to the external environment.
Upper Respiratory Functions
Anatomically, the respiratory apparatus consists of the airways (respiratory) tract and the respiratory section of the lungs. The respiratory tract performs mainly an air-conducting function, gas exchange occurs in the respiratory section of the lungs - venous blood is enriched with oxygen, and excess carbon dioxide is released into the alveolar air.
The respiratory tract is divided into upper and lower sections. The upper respiratory tract is the nasal cavity, nasopharynx, oropharynx. The lower respiratory tract is the larynx, trachea, extra- and intrapulmonary bronchi.
The mucous membrane of the respiratory tract performs a barrier and protective function, just like all the integumentary epithelium of organs in contact with the external environment. The upper respiratory tract is a kind of calorific-cleansing communication. Here the inhaled air is heated, purified - toxic substances and foreign particles are removed from it, and humidified. The inhaled air is effectively cleansed due to the fact that the respiratory tract is lined with ciliated epithelium, and glands located in the walls secrete mucus.
So, the airways perform the following functions:
- delivery of air to the respiratory section of the lungs;
- cleaning, warming, humidifying the air;
- barrier-protective;
- secretory - secretion of mucus.
Physiology of the respiratory system (as a science) studies the transport of respiratory gases under different conditions and the nervous mechanisms of breathing regulation.
The structure of the mucous membrane and the role of mucus in the respiratory tract
The mucous membrane of the upper respiratory tract has a multi-row ciliated epithelium, which contains cells that differ in function and form:
- ciliated - have shimmery cilia;
- goblet (secretory) - secrete mucus;
- microvillous (in the nasal passages) - chemoreceptor (provide the sense of smell);
Basal cells are cambial cells that divide and become goblet or ciliated.
Mucus is produced in secretory cells called goblet cells. Cells accumulate mucinogen - a substance that actively adsorbs water. Due to the accumulation of water, the cells swell, the mucinogen turnsmucin is the main component of mucus. The swollen cells look like a glass - the nucleus remains in the narrow part, the formed mucus remains in the expanded part. When too much mucus accumulates, the cell walls collapse, the mucus escapes into the lumen of the external nose and pharynx, manifesting itself as mucous secretions from the nose. Mucus is also secreted in the lower parts of the respiratory system, which is manifested by a productive - wet cough.
Mucus covers the epithelium of the respiratory tract with a layer up to 7 microns. During the day, a he althy person secretes up to 0.75 ml of this secret per 1 kg of weight, that is, if a person weighs about 60 kg, the volume of nasal secretion will be approximately 45 ml. During inflammation of the nasal mucosa, the volume can increase to one or two liters.
Mucus contains non-specific and specific defense factors, due to which it has antiviral and antibacterial effects. In addition, the layer of mucus protects the lining of the respiratory tract from various damages: thermal, mechanical, due to changes in the chemical composition of the air or its humidity.
Air purification mechanism
The upper respiratory tract is a system that effectively purifies the inhaled air. Air purification is especially effective when breathing through the nose. During the passage of air through the rather narrow nasal passages, vortex movements occur. Large particles of air dust hit the walls of the nasal passages, as well as the nasopharynx and larynx, at which time they stick to the mucus that covers the paths of the respiratory organs. The described mechanism for purifying atmospheric air is so effective thatparticles no more than 4-6 microns.
In the lower sections - the bronchi and trachea, the activity of the ciliated epithelium contributes to the purification of air from large dust particles.
Congenital reflexes - coughing and sneezing - also contribute to air purification. Sneezing occurs when large dust particles enter the nose, coughing occurs in the trachea and bronchi. These reflexes clear the airways of irritating agents and stop them from entering the lungs, therefore they are considered protective. When reflex sneezing, air is forcefully ejected through the nose, as a result, the nasal passages are cleared.
The role of the cilia in the airway mucosa
Any ciliated cell has up to 200 cilia on its surface. They are cylindrical in shape and contain special structures that provide contraction and relaxation. As a result, the cilia make oscillatory unidirectional movements - up to 250 per minute. The movement of all cilia is coordinated: their oscillation pushes mucus along with foreign bodies from the external nose towards the nasopharynx. The mucus is then swallowed and enters the stomach. The cilia of the nasal mucosa work best at a pH of 5.5-6.5 and a temperature of 18-37°C. With a decrease in air humidity, a decrease in temperature below 10 ° C, a change in acidity, the fluctuation of cilia stops.
Mouth breathing
When breathing through the mouth, the air bypasses the respiratory tract - it is not warmed, cleaned or moistened. Therefore, if the patient asks the question of how to breathe correctly - through the nose or mouth, then the answer is unequivocal. permanentbreathing through the mouth leads to various pathologies, primarily to an increase in colds. Breathing through the mouth is especially dangerous in children. Due to the constantly open mouth, the tongue does not rest against the arch of the palate and this leads to a variety of disorders - improper formation of teeth, bite, problems with pronunciation. Mouth breathing is not enough for full oxygenation of tissues, mainly the brain. As a result, the child becomes irritable, inattentive.
Functions of the nose
All inhaled and exhaled air passes through the nasal cavity. Here the air is warmed, cleaned and humidified. Allocate the main and secondary functions of the nose. The main ones include:
- respiratory;
- protective;
- olfactory.
Minor functions include:
- mimic;
- speech, or resonator - due to the cavity and paranasal sinuses, nasal sounds are created;
- reflex;
- tear duct (lacrimal canal opens into the lower nasal passage);
- excretory - excretion of toxins along with mucus;
- barofunction - used by divers and the military.
Anatomy of the nose
The anatomy of the nose and paranasal sinuses is quite complex. The structure of the nose and its sinuses is of great clinical importance, since they are located very close to the brain, as well as to many great vessels, which can quickly spread pathogenic agents throughout the body.
Nose anatomically includes:
- outer nose;
- nasal cavity;
- paranasal sinuses.
The structure of the outer part of the nose
The outer part of the nose is formed by a triangular bone-cartilaginous frame covered with skin. Oval holes - each nostril opens into a wedge-shaped nasal cavity, these cavities are separated by a septum.
The external nose (as an anatomical formation) consists of three parts:
- Bone skeleton.
- Cartilaginous part.
- Soft fabrics.
The bony skeleton of the external nose is formed by small nasal bones and frontal processes of the upper jaw.
The middle part and the lower two-thirds of the nose are made up of cartilage. The cartilaginous part consists of:
- lateral cartilage (superolateral);
- large alar cartilages located in the caudal part of the nose;
- additional cartilages located behind the large pterygoids;
- unpaired cartilage of the septum.
The configuration of the part of the external nose, located below the tip, depends on the shape, size, location of the medial and middle legs of the alar cartilages. Changes in the shape of the cartilage are very noticeable here, so this area is often treated by plastic surgeons.
The shape of the nose depends on the structure and relative position of the bone and cartilage components, as well as on the amount of subcutaneous fat, skin and the condition of some muscles of the nose. Exercising certain muscles can change the shape of the nose.
The soft tissues of the outer noserepresented by muscle, fat and skin.
The nasal septum is formed by bone, cartilage and a membranous portion. The following bones are involved in the formation of the septum: the perpendicular plate of the ethmoid bone, the vomer, the nasal bone, the nasal crest of the upper jaw.
Most people have a slightly deviated septum, but the nose looks symmetrical. However, often a deviated septum leads to impaired nasal breathing. In this case, the patient should contact the surgeon.
The structure of the nasal cavity
Three spongy whorls protruding from the side walls of the nostrils - the shells partially divide the nasal cavities into four open passages - the nasal passages.
The nasal cavity is conditionally divided into the vestibule and the respiratory part. The mucous membrane of the vestibule of the nose includes a stratified squamous non-keratinized epithelium and the lamina proper. In the respiratory part, the mucosa contains a single-layer multi-row ciliated epithelium.
The mucous membrane of the respiratory part of the nose is represented by two areas:
1. The mucous membrane of the upper nasal passages and the upper third of the nasal septum. This is the olfactory area.
2. The mucous membrane of the middle and lower nasal passages. Veins pass through it, resembling lacunae of the cavernous body of the penis. This cavernous part of the submucosal tissue is underdeveloped in children; it is fully formed only by the age of 8-9 years. Normally, the blood content here is small, since the veins are narrowed. With swelling of the nasal mucosa (rhinitis), the veins fill with blood. This leads to narrowing of the nasal passages, breathingdifficult through the nose.
Structure of the olfactory organ
The olfactory organ is the peripheral part of the olfactory analyzer, located in the olfactory region of the mucous membrane of the nasal cavity. Olfactory cells, or olfactory receptors, are bipolar neurons located around supporting cylindrical cells. The peripheral end of each neuron has a large number of thin outgrowths, which significantly increases the surface area of the neuron and increases the likelihood of odorous contact with the olfactory analyzer.
Supporting cells perform a supporting function and are involved in the metabolism of receptor cells. Basal cells, lying deep in the epithelium, are a cellular reserve from which both receptor and supporting cells are formed.
The surface of the epithelium of the olfactory part is covered with mucus, which performs special functions here:
- prevents the body from drying out;
- is a source of ions that are necessary for the transmission of nerve impulses;
- ensures the removal of the odorous substance after its analysis;
- is the environment in which the reaction of the interaction between the odorous substance and the olfactory cells takes place.
The other end of the cell, the neuron, combines with other neurons to form nerve threads. They pass through the holes of the ethmoid bone and go further into the olfactory bulb, located in the intracranial cavity under the frontal lobe and above the ethmoid plate of the ethmoid bone. The olfactory bulb functions as the olfactory center.
The structure of the paranasal sinuses
The anatomy of the human respiratory system is very interesting.
- The paranasal sinuses (sinuses) are located in the bones of the brain and facial skull and communicate with the nasal cavities. They are formed during the ingrowth of the mucous membrane of the middle nasal passage into the spongy bone tissue. There are several sinuses.
- The frontal sinus is a steam room located in the frontal bone. The frontal sinuses in different people can be developed to varying degrees, in some they are absent. The frontal sinus communicates with the nasal cavity through the frontonasal canal, which opens into the anterior semilunar fissure in the middle nasal passage.
- The maxillary sinus is located in the body of the upper jaw. This is the largest air cavity in the skull. In front of the medial wall of the sinus passes the nasolacrimal canal. The sinus outlet is located behind the nasolacrimal canal at the highest point of the sinus. There may be an additional hole behind and below this hole.
- The lattice labyrinth is a complex multi-chamber cavity.
- The sphenoid sinus is a steam cavity located in the body of the sphenoid bone. The floor of the sinus forms the vault of the nasopharynx. The hole is located in the anterior wall, connects the sinus with the upper nasal passage. The openings of the optic nerves are located in the upper lateral region.
