Jaw line. Anatomy: Lower jaw

The human body has a complex structure. One of the most interesting areas in terms of structure is the jaw. It performs many functions necessary for a normal life. For example, a toothless person will not be able to chew food, which will lead to indigestion. To prevent pathological changes, it is important to know the features of the upper and lower jaw: anatomy, disorders, treatment.

Functional and surgical anatomy of the human jaws

The maxillofacial system consists of a number of organs that take part in digestion, forced speech, and breathing. The location of these elements determines the shape and type of face.

The system is presented:

• skeleton, which consists of the zygomatic, nasal and jaw bones;
• organs involved in the formation of the food bolus and promoting it into the pharynx;
• facial, chewing muscles;
• , which produce a secretion for easy chewing of food and normal formation of a food bolus (soft and hard palate, cheeks, uvula and tongue);
• teeth designed for biting and chewing food;
• organs that capture food and close the mouth (facial muscles, lips);
• nerve receptors that allow you to sense taste.

The upper and lower jaws have different surgical and functional structures.

Anatomy of the upper jaw

The upper jaw occupies a central place among the bone tissue of the facial part of the skull. It performs the most important functions.

Among them:

• respiratory (forms the maxillary sinus, in which the air is heated and humidified);
• formative (creates the eye and nasal cavities, a partition between the nose and mouth);
• aesthetic (determines the setting of the cheekbones, the oval of the face, the attractiveness of a person);
• swallowing (ligaments and muscles of the jaw are involved in the process of swallowing food);
• chewing (teeth ensure chewing of food for normal digestion);
• sound-producing (together with the air sinuses and lower jaw, it forms different sounds).

Osteomyelitis of the jaw is a purulent-inflammatory lesion of the maxillofacial area due to infection. In this case, bone destruction is observed. Depending on the location, osteomyelitis of the jaw accounts for more than 30% of all cases. More often the disease affects the lower jaw bone.

Anatomical structure of the teeth of the upper and lower jaw

From the crown, neck, root. The crown is covered with enamel and protrudes above the edge of the gum. The neck is located between the root and the crown. The root is embedded in the alveolus of the jaw bone and consists of dentin. Depending on functionality, the number of roots can vary from 1 to 3 pieces. Inside, the dental unit is represented by a cavity, the shape of which follows the crown.

Anatomical root canals and apical foramina coincide with the number of roots. The wall of the cavity adjacent to the closing surface is called the vault. Anatomically, the cavity consists of loose connective tissue - pulp.

Human teeth

There are three functionally oriented groups of teeth:

1. anterior frontal;
2. biting;
3. lateral.

The shape of the tooth depends on the function performed. Biting elements are also represented by incisors. The former have a pointed conical shape, the latter have a cutting edge. There are 12 biting teeth in total. The chewing group is characterized by molars and. They have a multitubercular surface. The line that connects the most convex parts of the tooth is called the equator. It divides the chewing element into gingival and occlusal zones. Each tooth has its own dimensions (thickness, height and width).

Thus, the jaw has a complex structure. It performs a number of important functions and ensures normal life activities. There are a number of pathologies of the jaw bones. Each disease requires the development of a specific treatment regimen.

Healthy and beautiful teeth are a decoration for any person. Pink gums, an even bite and a snow-white smile indicate that a person has excellent health and, in general, is considered a sign of success. Why is so much attention paid to teeth and why did this happen?

General concepts about teeth and their classification

Teeth are special bone formations that carry out the primary mechanical processing of food. People have long been accustomed to eating rather tough foods - meat, grains, plant fruits. This food requires considerable effort to process, and therefore healthy teeth have always been considered an indicator that a person eats a varied and good diet.

To begin with, what you need to know about teeth is the only organs in the human body that cannot be restored. Both their apparent reliability and fundamental nature are quickly violated by bad habits and poor care.

And if milk, primary teeth are fragile precisely because of their temporary purpose, then the molars are given to a person for the rest of his life. In general, the entire dentition in a person is divided into the following types:

• fangs;
• incisors (lateral and central, also called lateral and medial);
• molars or large molars (this also includes the upper and lower wisdom teeth that grow in a person in adulthood or young age);
• premolars or small molars.

As a rule, the location of the dentition on the upper and lower jaw is recorded using the so-called dental formula. For molars and milk teeth, this formula differs only in that the molars are most often designated using Arabic numerals, and the milk teeth - with Latin numerals.

For an average adult, the dental formula looks something like this: 87654321|12345678. The numbers indicate teeth - any healthy person must have one canine, 2 incisors, 3 molars on each side, 2 premolars on the upper and lower jaw. As a result the total quantity is 32 pieces.

For babies who have not yet had their primary teeth replaced, this formula looks different, since there can be as many teeth as approximately 20 pieces. As a rule, temporary teeth erupt by 2–3 years of age, and by 9–12 years they are completely replaced by permanent teeth. However, not all people can boast of having all 32 sprouted teeth.

Since wisdom teeth or third molars can appear in adulthood, or they can remain completely in their infancy all their lives, and in this case in a person’s oral cavity there will be 28 teeth. Moreover, the structure of the lower and upper jaws has certain differences.

Anatomical structure

The anatomy of a human tooth suggests that it is conventionally divided into 3 parts: root, neck and crown. The crown is the part that rises above the gum; it is covered with enamel - the strongest tissue that protects the tooth bone from the negative effects of acids and bacteria. There are several types of crown surfaces:

The neck is the part that is between root and crown, connecting them, covered with cement and closed by the edges of the gums. The root is the part with which the tooth is attached to its socket. Taking into account the classification type, the root can have one or more processes.

Histology

The histological structure of all teeth is exactly the same, but all of them have a different shape, taking into account the specific function they perform.

Enamel. This durable fabric, which consists of 95% of various salts such as zinc, magnesium, copper, strontium, fluorine and iron. And 5% consists of substances such as carbohydrates, lipids, proteins. In addition, the enamel contains a liquid that participates in physiological processes.

At the same time, enamel also has outer shell, which is called the cuticle, it covers the chewing surface, but over time the cuticle tends to wear off and become thinner.

The basis of the bone tissue of the tooth is dentin is a collection of minerals surrounding the root canal and the entire dental cavity. Dentin tissue contains a large number of tiny channels through which metabolic processes take place and nerve impulses are also transmitted through the channels.

Root structure: pulp and periodontium

The cavity inside the tooth is formed by the pulp - this is a loose and soft tissue, penetrated through and through by nerve endings, as well as lymphatic and blood vessels.

The structure of the roots looks like this. The root is in a special hole - the alveolus, in the bone tissue of the jaw. The root, like the crown, consists of mineral tissue - dentin, covered on the outside with cement.

Root ends with apex, through its opening pass blood vessels that feed the dental bone. The number of roots can vary depending on the functional purpose of the teeth, from 1 root in the incisors to 5 in the chewing teeth.

Periodontium is connective tissue, which fills the gap between the jaw socket and the tooth root. The fibers of the tissue, on the one hand, are woven into the cement of the root, and on the other, into the tissue of the jaw bone, due to this the tooth is firmly attached. In addition, through the periodontal tissue, the feeding elements of the blood vessels can enter the dental tissue.

Description of the dentition

Incisor teeth. The human jaw is symmetrical and contains the same number of teeth of each type. But there are certain anatomical features of the upper and lower jaw. Let's look at them in more detail.

Incisors are the front teeth. A person has eight of them - 4 at the bottom and 4 at the top. Incisors are needed to bite food and separate it into parts. The peculiarity of the structure of the incisors is that they have a flat, chisel-shaped crown with rather sharp edges.

On anatomical sections there are three tubercles, which are erased throughout life. On the jaw from above two central incisors– in its group the largest of all incisors. The lateral incisors are similar in shape to the central ones, but smaller in size.

What is noteworthy is that the immediate cutting edge of the lateral incisor also has three tubercles, and often takes on a convex shape as a result of the development of the central tubercle. The root of the incisor takes the shape of a cone, and is flat and single. A distinctive feature of the incisor is that on the side of the tooth cavity there are three pulp tips, corresponding to the tubercles of the cutting edge.

The anatomy of the upper teeth is slightly different from the structure of the lower dentition, so in the lower jaw everything is exactly the opposite. Middle incisors are smaller unlike the lateral ones, they have a shorter and thinner root than the incisors on the sides. The outer surface of the cutter is slightly convex, while the inner surface is concave.

Incisor crown, side view curved towards the lips and very narrow. The cutting edge has 2 angles - in the center, more acute, and inside - more obtuse. The roots have longitudinal grooves.

Chewing teeth and fangs

Fangs are used to break down food into smaller pieces. The anatomy of the fangs is such that there is a groove on the inside of the crown; it disproportionately divides the crown into 2 parts. The cutting edge of the fangs has one pronounced and developed tubercle, this makes the cone-shaped crown often similar to the fangs of a predator.

The canine on the lower jaw is narrower in shape, the ends of the crown are concentrated in the medial tubercle. The canine root is flat, inclined inward and the longest, unlike the roots of other teeth. In humans 2 fangs on both jaws. The lateral incisors with the canines form an arch, where the transition from the incisors to the chewing teeth begins in the corner.

Let us consider the structure of the small chewing tooth first, and then the large chewing tooth. Their main task is careful processing of food. This function is performed by molars and premolars.

Premolars

The first premolar (No. 4 in the dental formula) differs from the incisors and canines in its prismatic shape, and there are convex surfaces on the crown. The surface has 2 tubercles - lingual and buccal, with grooves between them.

The buccal tubercle is much larger in size than the lingual one. The root of the first premolar has flat shape, but with a slight bifurcation into the lingual and buccal parts.

The second premolar is similar in structure to the first, but its buccal surface is much larger, and the root has a compressed anteroposterior direction and cone-shaped. In the first lower premolar, the chewing surface is inclined towards the tongue.

The second premolar is larger than the first due to the fact that both tubercles are symmetrical and equally developed, and the depressions in the enamel between them have the shape of a horseshoe. The root is the same as that of the first premolar. In a person's dentition there are 8 premolars, four on each side (on the lower and upper jaws).

Molars

In the upper jaw, the first molar is the largest. Its crown is similar to a rectangle, and the chewing surface is diamond-shaped with 4 tubercles. This molar has three roots: one straight - the most powerful, and two buccal - flat, deflected in the posterior direction.

When the jaws close, the first molars rest against each other and form a kind of “limiter”“, because of this, they undergo significant stress throughout a person’s life.

Second molar has smaller dimensions. The roots are the same as those of the first molar. The structure completely coincides with the location of the premolars described above.

On the lower jaw, the first molar for chewing food has five cusps. This molar two roots– front with two channels, rear – with one. In this case, the anterior root is larger than the posterior one. In the lower jaw, the second molar is similar in structure to the first. The number of molars in humans is the same as the number of premolars.

The third molar is called " wisdom tooth“, and in total a person has four of them in the dentition, two on each jaw. On the jaw below, the third molar has many variations in cusp development. As a rule, there are five of them. And, in general, in a person the structure of a “wisdom tooth” is the same as the structure of a second molar, but the root usually resembles a very powerful and short trunk.

Baby teeth

The histological and anatomical structure of a baby tooth is similar to the structure of a molar tooth, however, there are certain differences:

In the end, I would like to note that, naturally, the arrangement of teeth in the jaw, their structure, closure have an individual character for each specific person. But the dental apparatus of each person performs vital functions throughout life, therefore, over time, the dental structure changes.

We must not forget that in dentistry, many pathological processes appear in childhood, so you need to monitor the condition of your teeth from childhood. This will help avoid problems in the future.

Despite their apparent simplicity, teeth are quite fragile and complex system, with a multilayer structure, where each layer and element has its own specific purpose, as well as certain properties. And the fact that teeth change only once during a lifetime makes the structure of the human jaw different from the anatomy of the jaw of other representatives of the fauna.

In the center of the face is the upper jaw, which is a paired bone. This element connects to all the bones of the face, including the ethmoid bone.

Bone helps form the walls of the mouth, nose, and orbit.

Due to the fact that the bone contains a large cavity inside itself, which is covered with a mucous membrane, it is considered air-bearing. Anatomy of the upper jaw – 4 processes and body.

The nasal and anterior surfaces are components of the body. Also components are the infratemporal and orbital surfaces.

The orbital has a smooth texture and a shape with three corners. The lateral side of the jaw element is connected to the lacrimal bone. The posterior side, located from the lacrimal bone, connects to the plate of the orbit, after which it rests on the palatal-maxillary suture.

The infratemporal surface is convex and has many irregularities. A noticeable tubercle on the upper jaw is formed from the infratemporal surface. The element is directed to the infratemporal region. There may be up to three alveolar openings in the surface. The holes lead into channels with the same name. They are designed for the nerves to pass through and connect to the back teeth of the jaw.

The anterior surface abuts the buccal part of the process, but it is not possible to observe a noticeable boundary between them. On the alveolar process of that area there are several areas of bone with elevation. Toward the nasal region, the surface becomes a nasal notch with a sharp edge. These notches are the limiters for the pyriform aperture, which leads into the nasal cavity.

The anatomy of the nasal surface is complex: at the top of the posterior part of the surface there is a cleft that leads into the maxillary sinus. On the posterior side, the surface is connected by a suture to the palatine bone. One of the walls of the palatine canal, the palatine sulcus, runs along the nasal area. In the anterior part of the cleft there is a lacrimal groove, limited by the frontal process.

Processes of the paired bone

There are 4 known branches:

• alveolar;
• zygomatic;
• palatine;
• frontal.

These names were derived from their location on the jaw.

The alveolar process is located on the lower part of the upper jaw. It has eight cells for teeth, which are separated by partitions.

The zygomatic process is attached to the zygomatic bone. Its task is to evenly distribute the pressure generated as a result of the chewing process throughout the thick support.

Part of the hard part of the palate is the palatine process. This element is connected to the opposite side through a median seam. The nasal ridge, which connects to the vomer, is located along the seam, on the inside, which is on the inside part located towards the nose. Close to the front portion of the element there is a hole that leads into the cutter channel.

The lower part of the canal has an uneven surface with noticeable roughness, and has longitudinal grooves for nerves and blood vessels to pass through. There are no rough spots on the top. The incisive suture can be seen mainly in front of the section, but there are exceptions due to the individual structure of the human jaw. The suture itself is necessary to separate the incisive bone from the upper jaw.

The frontal process of the maxilla is raised to the upper part and has connections with the frontal bone. There is a ridge on the side of the process. Part of the frontal process joins the middle turbinate.

The structure of the human upper jaw and all its processes is a complex system. Each section of the upper jaw has a separate function, and all of them are designed for a specific job.

Jaw function

Thanks to the work of the upper jaw, the chewing process necessary for the primary processing of food occurs.

The jaw is responsible for the following processes:

• distribution of the load on the teeth while chewing food;
• is part of the mouth, nose and partitions between them;
• helps determine the correct position of the processes.

At first glance, it seems that there are not many functions performed by the upper jaw, but all of them are vital for the full existence of a person. Therefore, when problems arise with the elements, one or more functions are disrupted, which significantly affects the state of human health.

Peculiarities

There are several interesting topographical anatomical features that relate to the teeth in the maxilla. Basically, the upper jaw has the same number of teeth as the lower jaw, but there are differences in the structure and number of roots.

It has been proven that in most cases, a person’s wisdom tooth erupts on the upper jaw on the right side. There is no exact definition why this happens.

Since the lower jaw has thicker bone, problems with tooth extraction do not arise, unlike the upper jaw. Due to thinner bone, more care and handling of the tooth being removed is required. For this, specialized bayonet tweezers are used. In addition, more research is needed for reinsurance. If the root is removed incorrectly, there is a risk of a serious fracture. Any surgical procedure should be performed only in a hospital setting with the help of a specialist. Pulling teeth yourself is dangerous because you can damage the entire jaw or introduce an infection into the blood.

Possible diseases

Due to the fact that the elements of the upper jaw collectively have a smaller volume, it is injured several times more often than the lower jaw. The skull is tightly fused to the upper jaw, which makes it immobile, unlike the lower jaw.

Illnesses can be congenital, hereditary or resulting from injury. Sometimes edentia occurs (anomaly of one or more teeth).

Most often the jaws suffer from fractures. A fracture can occur due to impact with a hard surface, such as a fall. In addition, dislocation can become a pathology. Dislocations sometimes occur even at home without external influence. This happens when the jaws are positioned incorrectly while chewing food. A sudden careless movement causes the element to “go behind” the other jaw, and due to pinching, it is not possible to return it to its original position on its own.

Fractures of the lower section take much longer and are more difficult to heal. This is due to the fact that the lower jaw is mobile, and for a full recovery it is necessary to remain motionless for a long period of time. The upper section does not have this problem due to its complete attachment to the skull.

In some cases, a person develops a cyst on the upper jaw, which can only be removed through surgery. The process is voluminous and hazardous to health.

In addition to such diseases, the occurrence of sinusitis is known. This process mainly occurs as a result of improper dental treatment. This happens because the maxillary sinus becomes inflamed and blocks the sinuses.

Sometimes an inflammatory process of the trigeminal or facial nerve occurs. With such inflammation it is difficult to make a correct diagnosis. In some cases, a person has a completely healthy tooth removed.

Also, do not forget about a more serious disease that can affect not only the upper, but also the lower jaw. Cancer is the most dangerous disease, and some forms of this disease are treated surgically. In more rare cases, other methods of therapy are prescribed, however, the disease itself may not manifest itself for a long time.

This is not a complete list of diseases that may be associated with the upper jaw. Some pathologies are rare and are detected only after a comprehensive diagnosis.

Symptoms of pathologies

Each jaw pathology has symptoms that will differ from others.

• For example, with a fracture, the patient experiences severe pain and the inability to move the jaw. Severe swelling and bruising often occurs;
• Symptoms of a bruise are: pain, bruising, difficulty in chewing. With a bruise, the function is not completely absent, but the person is not able to fully chew food;

• With sinusitis, pain occurs that radiates to the lower jaw, eyes or nose. A person cannot breathe fully. A severe headache appears, and pus or mucus comes out of the nose. In some cases, the temperature rises, nausea, dizziness, and vomiting appear;
• The tumor may not have any symptoms at first, but after some time pain will appear not only in the jaw, but also in the joint. In some cases, there is a change in facial symmetry. The functioning of the joint is disrupted, so it is impossible to fully open or close the mouth. This pathology can affect not only the upper element;
• If the ailment is a problem with the teeth, then most often the causes are holes in the tooth, bleeding gums. The tooth may become loose or break off in pieces. In this case, the disease is accompanied by acute periodic pain, which will only intensify over time.

Most diseases are characterized by pain. It is important to make a correct diagnosis, and only then begin treatment.

Diagnostics

Pathologies of the upper jaw can be diagnosed at an appointment with a dentist or therapist. The doctor learns about the symptoms that bother the patient, then examines the oral cavity. To confirm a possible diagnosis, the use of hardware research methods will be required.

To get a complete picture of the condition of the jaw, it is necessary to take an x-ray. The image will immediately show the fracture or bruise, as well as its degree. X-rays allow you to determine the presence of pathologies associated with teeth. In addition, in some cases, it is recommended to turn to computed tomography or magnetic resonance imaging procedures to obtain a more accurate result. Such studies are necessary if it was not possible to make a final accurate diagnosis after receiving x-rays.

Certain types of pathological processes require laboratory tests, such as blood and urine.

You should not delay contacting a specialist, as some ailments develop rapidly and carry with them many unpleasant and dangerous consequences.

Therapeutic measures

Treatment depends on the diagnosis. In case of a bruise, you need to apply a cold compress and reduce the load on the jaw as much as possible. It is advisable to give up solid food for a while.

A fracture involves the complete exclusion of solid food for a long period of time, while the jaws are sometimes fixed in such a way that it is not possible to make any movements with them.

The cyst and any other growths are removed during surgery. If the neoplasm is oncological in nature, radiation or chemotherapy may be used. Their necessity is determined during repeated diagnostics.

If the ailment is related to the teeth, they are sometimes replaced using the clasp prosthetics procedure. During the procedure, removable dentures are installed. The clasp arch of the upper jaw allows you to create the appearance of the integrity of the teeth. With their help, a person can chew food. Such prosthetics are selected individually, based on the condition of the teeth.

Typically, the teeth in the upper jaw are partially replaced, and complete installation of dentures will require another procedure, where the dentures will no longer be removable. In the case of fixed dentures, there is a high risk of their rejection by the body, and a removable arch is suitable for everyone who has at least a few intact teeth. A partial removable denture for the upper jaw is expensive, but it is durable, and if quality materials are selected and used correctly, it can be worn for a very long time.

Braces help straighten teeth. Their task is to move all the teeth along the desired arch. This process takes several years. It also uses an arch frame to which the teeth are attached.

Some pathological conditions, such as congenital abnormalities or the consequences of serious injury, are corrected with rhinoplasty. The scar is not visible, which is an advantage for many people. The rhinoplasty procedure is expensive, but for people with congenital anomalies of the upper jaw, it is a way out.

When is surgery necessary?

It is extremely rare that a maxillectomy procedure is required.

A maxillectomy is an operation to remove the upper jaw. Indications for such a procedure may be oncological tumors that affect the processes or body of the element. Also, an indication for jaw removal is a benign neoplasm if it progresses and the process cannot be stopped with the help of drugs.

The procedure has contraindications:

• states of general malaise;
• pathologies of an infectious nature;
• specific diseases that are in an acute stage.

Also, the procedure is not performed if the disease has reached a stage at which removing part of the jaw will not help or there is a risk of worsening the condition.

Before any operation related to the jaw, a thorough examination of all affected organs and those closest to this area is required. It is important to remember that there is always a risk of complications, but if the percentage is low and no contraindications are identified, then the operation is performed to improve the patient’s condition.

Possible complications

Despite the fact that most pathological processes associated with the elements of the upper jaw proceed safely, there is a risk of some complications, for example, a fracture may occur during the procedure, and if the incision was made incorrectly, one of the nerves may be hit, which can lead to facial paralysis.

But even if the operation was performed correctly, there is a risk of blood poisoning if the instruments were not sufficiently disinfected. The period of rehabilitation and compliance with the recommendations of the attending physician are important, since if they are not followed, treatment can be considered meaningless, and this applies to any disease.

Complications arise if you do not see a doctor on time. Even a small and harmless neoplasm, in the absence of proper treatment, develops into dangerous pathologies, for example, into a cancerous tumor, which is difficult to get rid of.

Dental diseases need to be treated in a timely manner, without waiting for acute pain. The disease can spread from the teeth to the bone tissue of the jaw, and then the disease will progress throughout the body in the form of infection.

Preventive actions

To avoid serious problems with the jaw, you need to take care of its condition from a young age. If the first signs of improperly growing teeth appear in a child or obvious deviations from the norm in the structure of the jaw are visible, it is better to consult a doctor.

It is better to correct any congenital anomalies while the child is small, until the bone is fully formed and there is an opportunity to help it correct itself without resorting to more serious surgical interventions.

Prevention of dental disease is timely visits to the dentist, proper nutrition, and daily brushing of teeth. To reduce the risk of developing dangerous pathological processes, you need to visit a doctor at least once a year.

It will not be superfluous to undergo an annual comprehensive examination of the whole body. In addition, you need to be careful and avoid injuries, since any injury causes serious harm to the entire body.

Do not forget about the state of a person’s psycho-emotional background, since in the presence of visible defects, most people feel insecure. You should not delay the correction of serious visible deformations, since the formed bone tissue is more difficult to rebuild, and the risk of complications is much higher.

The key to a healthy body is eating proper, healthy food, mandatory consumption of solid varieties of food, and careful hygiene procedures. By following simple rules, it is possible to avoid the development of many pathological processes, which subsequently bring not only an unsightly appearance to the face, but also noticeable discomfort.

If you suddenly become bothered by painful sensations that do not go away or appear more than once, you should immediately seek help from a specialist, since pain is one of the first signs of the development of dangerous diseases. Compliance with preventive measures cannot always prevent the development of the disease, but it significantly reduces the risk of its occurrence.

You should not ignore even mildly noticeable discomfort if it appears regularly, since the most dangerous ailments often do not have pronounced symptoms, but the consequences of untimely treatment can be irreparable. Also, you should not self-medicate, even if you know the exact diagnosis.

Not all therapeutic measures using traditional recipes will be effective; some of them cause significant harm. Neglecting the doctor’s advice during treatment or during the rehabilitation period will lead to a worsening of the condition and aggravation of the course of the disease.

The only movable part of the skull is the lower jaw, which is horseshoe-shaped. It plays a very important role in the process of digestion, on which human life depends. Her injuries are the cause of many diseases associated with poor nutrition. The jaw moves due to the chewing muscles, which are constantly in action.

The lower jaw is an active part of the facial skeleton, consisting of a pair of similar bones that finally fuse by two years. Each of them has the same structure - body and branch. At the site of their fusion, a slight line is formed, which in old age forms into a pronounced bony protrusion. It has seven paired muscles that ensure its movement, which are considered one of the most developed muscles of the human body. The jaw itself, given its shape, can be classified as flat bones. The anatomy of the lower jaw has a symmetrical structure.

Body

The body of the lower jaw has a curved, C-shape, divided into two horizontal halves - the alveolar, where the teeth are located, and the base. The outer side of the base has a convex shape, while the inner side is the opposite of the concave shape. The alveolar part is represented by a number of dental alveoli (root cavities). Both parts of the body connect at different angles, creating a basal arch, which determines the shape or size of the body, measured by a special value.

The highest point of the body is concentrated in the middle, in the area of ​​the incisors, and the lowest height is observed in the area of ​​the premolars (a pair of molars located behind the incisors). When a cross section of the body is made, its shape changes depending on the number and location of dental roots. The area where the anterior alveoli are located looks like a triangle with the base pointing downwards. And in the area of ​​the premolars, the shape resembles a triangle, the base of which is directed upward.

In the center of the outer side of the body there is a chin protuberance. It is he who indicates that the human jaw is formed from two symmetrical bones. The chin is located at an angle of 46-85° relative to the imaginary horizontal line. On both sides of it are the mental tubercles, located near the base. Above the chin there is a small opening of the root tract, through which blood and nerve branches are discharged.

Usually its location does not have a clear location, and may vary depending on several factors. As a rule, it is located on the line of the fifth alveolus, but can be shifted towards the fourth, being at the junction of the 5th and 6th teeth. The passage has a rounded shape, can sometimes be divided, and is located at a distance of 10-19 mm from the base of the body. With an unhealthy alveolar part, its location changes, being localized somewhat higher.

The lateral sides of the body have a curved line called an oblique ridge, one end of which is at the level of the 5-6th tooth, the other smoothly flows into the anterior section of the branch.

In the inner part of the body, closer to the center, there is a bone spike, which can sometimes have a forked shape. It is called the mental spine. This is where the tongue muscles originate. If you go lower, a little to the side, you can see the digastric cavity. The digastric muscle is attached to it. Above this fossa there is a small depression called the sublingual fossa, where the salivary gland is located.

A little further, closer to the back of the body, is the mylohyoid line, from which the mylohyoid, as well as the superior constrictor muscle of the pharynx, rushes. This line runs in the middle of the digastric and hyoid fossa, at the level of 5-6 teeth, and its end is located in the inner part of the branch. And below it, opposite 5-7 teeth, there is a depression for the salivary gland.

The alveolar half of the body consists of 8 alveoli on both sides. The dental cavities are separated by interalveolar walls. The partitions that cover the tooth from the side of the cheeks are called vestibular, and those that look towards the pharynx are called lingual. In the upper plane of the body, the dental canals coincide with the alveolar eminence, which are very clearly visible in the area of ​​the canine or first molar tooth. The anatomical shapes and sizes of the alveoli are different, and their indicators depend on the purpose. Between the front teeth and the protrusion of the chin there is a subincisal cavity.

The dental recesses of the first incisors are compressed on both sides, and the root extends slightly towards the vestibular plate, as a result of which the width of the inner wall is thicker than the outer one. The fossae of the canines and premolars are round in shape, which ensures strength and uniform pressure. Moreover, they have the deepest alveoli, and the thickness of the septa significantly exceeds the incisal thickness. The alveoli of molars have root walls, since their roots are bifurcated.

The first two molar teeth have only one pier, and the recess of the third molar can have a different shape, which can change over time. This is explained by the variability of the root part of the molar. Most often, the alveolus of this tooth has the shape of a cone, without a single septum, but there are nests that have one or even two septa. Their walls thicken due to the hyoid line. This localization promotes reliable fastening of the teeth, protecting them from loosening.

The part of the body located behind the molar teeth has a triangular shape. It is called the retromolar fossa, and on the side of the outer plate of the alveolar region there is a mandibular recess, which is localized from the 2nd or 3rd molar to the coronoid.

The structure of the alveolar region of both parts is similar. Its walls are presented in the form of a two-layer plate: internal and external, and the lower third of the alveolar region under the internal plate is filled with the cavernous body, in which the mandibular canal is located. Capillaries, arteries, and nerve branches pass through it. The hole located in the inner part of the branch is its beginning, and it ends on the outer part of the chin. The outlet has a bent shape with a protrusion directed to the lower anterior part at the bottom of the 2nd and 3rd dental sockets, located between the molar septa.

From this canal there are branches along which nerves and capillaries approach the dental roots and open at the very bottom of the molar recesses. Further, the channel narrows, rushing towards the center line. From here it supplies branches that feed the front teeth.

Branch

The branch is also divided into two planes: internal and external. But besides this, it has front and back sides, which pass into synovial processes - coronoid and condylar, which are separated from each other by a deep notch. One is intended to attach the temporalis muscle, and the other is for the base of the joint that connects both cheekbones. The shape of the branch does not have a specific appearance.

The condylar process of the mandible appears in the form of a neck and head, which is united with the mandibular notch of the temporal region through the articular part. On one side of the surface of the neck there is a wing-shaped depression, which is intended for attachment of the external pterygoid muscle.

The articular process of the lower jaw has a flattened shape. It is localized in such a way that the axes, mentally drawn through the maximum size of both heads, have an intersection point at the large rear hole at an angle of 120 to 178 degrees. Its shape and condition have nothing in common and depend on the functioning of the temporomandibular joint. Movements that contribute to changes in the size and direction of the joint affect the condition of the articular heads.

The frontal edge of the branch on both sides of the outer plane of the body is formed into a curved line, and closer to the axis it reaches the outer molars, creating a retromolar notch. The middle part of the ridge, which arises at the point of contact of the frontal part and the walls of the dorsal molar recesses, is called the buccal ridge, where the buccal muscle takes its base.

The back of the branch smoothly connects to the base of the body at angles ranging from 110 to 145 degrees and can change over time (122-133 degrees). In newborns, this value approaches 150 degrees, and in adults, the angle decreases, taking into account the preservation of teeth and the full functioning of muscles. In people of retirement age, when tooth loss occurs, it increases again.

The outer side of the branch is presented in the form of a tuberous surface, which occupies its largest segment, including the angle of the jaw. The chewing muscle is attached to it. From the inside of the branch, in the area of ​​the angle of the cheekbone and adjacent sections, there is a pterygoid mound, on which the median muscle is fixed in the shape of a wing. Here, just in the center, there is a hole protected by a temporary bony protrusion called the tongue. Slightly above it is localized the mandibular ridge, which is the base point of the maxillary-pterygoid and maxillary-sphenoid ligament.

Most often, the branches of the lower jaw are directed outward so that the gap between the condylar apophyses of both branches is longer than the segment between the facial edges of the jaw angles. The difference in the deviation of the branches is largely determined by the shape of the upper part of the facial bone. If it is quite wide, then the branches are turned out to a minimum, and with a narrowed face shape, on the contrary, they are turned out to the maximum.

In the first case, the value can range from 23 to 40 mm. The width and depth of the cutout also have distinctive parameters: the width ranges from 26 to 43 mm, and the depth from 7 to 21 mm. In a person with a wider facial bone, these indicators are maximum.

Functions of the lower jaw

The muscles of the occipital sections of the branches are largely responsible for the force of compression of the teeth. The preservation of healthy bone in such conditions directly depends on age-related changes. The angle of the jaw must constantly change, from birth to old age. More suitable conditions for counteracting the resulting load are characterized by changing the jaw angle to 70 degrees. This value occurs when the position of the outer corner changes, between the surface of the base and the back of the branch.

The overall compressive strength reaches 400 kgf, which is 20% higher than the resistance of the upper jaw. This indicates that idle loads during tooth compression do not pose any danger to the chewing bones associated with the upper part of the skull. It turns out that the lower jaw is a kind of fuse, capable of destroying solid objects and being damaged without affecting the upper jaw.

This property must be taken into account by dentists when replacing teeth. The jawbone has a compact substance that gives it hardness. Its indicators are calculated using a certain formula or special meters and should be 250-356 NV. Individual areas of the teeth have their own significance, and in the area of ​​the 6th tooth it reaches its maximum. This proves its importance in the alveolar series.

From the information described above, some conclusions can be drawn regarding the structure and activity of the chewing bones. Its branches are not adjacent, since their upper surfaces are slightly wider than the lower ones. The coincidence is equal to 18 degrees. Moreover, the leading edges of the branches are one centimeter closer than the rear ones.

The triangular bone that connects its apexes and the junction of the jaw has almost equal sides. The right and left sides are similar, but asymmetrical. All indicators and functions of the lower jaw largely depend on the age category and change as the body ages.

Lower jaw injuries

Trauma to the maxillofacial region is one of the most unpleasant lesions of the human skeleton. Such injuries require long-term treatment and heal very slowly. And the most unpleasant thing is that eating food does not bring pleasure, but only painful sensations. As a result, stomach and digestive problems arise. The main cause of injury is physical impact from falls, blows and other accidents. The most common of them are bruises, dislocations and fractures.

In addition, any injury can cause all sorts of complications. This is usually due to lack of proper treatment and ignoring the problem. If a bruise, even a minor one, is not treated, post-traumatic periostitis may occur, often resulting in deformation of the bone, which will protrude over time.

Complications can be directed to pathological and physiological disorders of the alveolar region: tooth displacement, malocclusion, the occurrence of interdental spaces.

If the jaw is injured, it is unlikely that you will be able to avoid the feeling of discomfort and pain. All actions that she performs - talking, chewing, swallowing - will be accompanied by acute pain. However, some unpleasant moments can be avoided if you contact a traumatologist or surgeon in a timely manner and follow their instructions during the treatment process.

Bruised jaw

One of the simplest disorders of the masticatory apparatus is a bruise. This type of injury is characterized by the absence of external physical damage to the skin and bone. The most common cause of bruises is physical contact with a hard surface or a blow from a heavy object. The severity of the injury depends on several factors: material, force, mass, speed.

A bruise can be identified by the following signs:

• Sudden change in body temperature.
• Soreness.
• Redness of the skin.
• A specific sound when moving the cheekbones.
• Severe pain while eating.
• Your head may hurt.

A bruise can be easily identified by the presence of external signs, which are described above. The patient can provide first aid to himself. To do this, it is enough to apply a cooling compress to the affected part of the jaw, applying a bandage tightly for 10-15 minutes. It will relieve swelling and reduce pain. After this, you must visit your doctor's office to begin treatment.

In the absence of appropriate help, undesirable consequences may occur: tooth loss or deformation of certain areas.

Dislocation

The most common cause of dislocation is sudden up and down movements, as well as teeth breaking hard objects. These factors can provoke deformation or displacement of the articulating head, which subsequently leads to severe injury. This happens due to the ability of the jaw to actively move in different directions, which often leads to its deformation. But adjusting it - pushing it out or pushing it in - is not so easy and very painful.

The symptoms of a dislocation differ significantly from the symptoms of a bruise in their increased intensity. In addition, the following changes may be observed:

• constant pain;
• difficulty closing the jaws;
• copious amounts of saliva;
• the ability to visually observe the displacement of the jawbone.

Dislocation can have two degrees of complexity: unilateral dislocation, when deformation of one articular head occurs, and bilateral dislocation, when displacement of both joints is observed. You can determine the type of injury yourself. Deviation of the chin with the slightest movement to one side indicates a unilateral dislocation.

Fracture

The most dangerous injuries to the masticatory apparatus are those associated with bone fractures. As a rule, with this form of injury, various parts of the bone base can be affected. It can be caused by a fall, blow, accident or other circumstances.

It may have different localization depending on the area of ​​the lesion - complete or partial destruction of the bone structure. Another cause of a fracture may be a tumor disease, hypertrophy of the masticatory muscles, or brain dysfunction, when a person may lose consciousness, fall, or be injured.

The danger of fractures is that when the bone is destroyed, other internal organs of the head located in this area can be damaged. This may damage the airways, ligaments, tendons, tongue or circulatory system.

Fractures are accompanied by the following symptoms:

• unbearable pain;
• cyanosis;
• nausea;
• sudden confusion in the head;
• swelling;
• lethargy.

It is clear that the word diagnosis is inappropriate here, since signs of a fracture are visible to the naked eye. However, other diagnostic methods are needed in order to determine its extent, as well as the presence of possible complications. Sometimes, using fluoroscopy, you can detect a false joint of the lower jaw, which is formed when a layer of bone tissue is lost - pseudarthrosis.

If a person receives such an injury, the first thing you need to do is call an ambulance, and while it arrives, you need to take first aid measures: calm the victim, then try to fix the affected bone, and if there is bleeding, stop the bleeding. To do this, you can use clean tissues if it is not possible to obtain bandages or napkins. If the tongue is swallowed, measures must be taken to fix it, and then remove any remaining blood from the oral cavity if the injury is so serious. This is done so that the victim has the opportunity to breathe calmly and does not panic or lose consciousness.

The jaws are the basis of the facial skeleton. Not only the beauty of the profile, but also the functionality important for life depends on their anatomical structure. They enable chewing, swallowing, breathing, speech, formation of cavities for sensory organs and much more. According to human anatomy, the upper jaw is paired, and the lower jaw is unpaired.

Structure of the upper jaw

The structure of the human upper jaw suggests the presence of four processes:

• palatine;
• alveolar;
• zygomatic;
• frontal.

Human jaws.

There are four surfaces on the body of the upper jaw:

• front;
• infratemporal;
• nasal;
• orbital.

Unlike the lower jaw, in the anatomy of the upper jaw, the connections with the rest of the bones of the skull are fixed. The anterior surface is concave, and below it passes into the alveolar process. On the alveolar processes, the upper jaw has cells with partitions where the roots of the teeth are located. The most significant elevation is provided for the canine.

In the center of this part of the jaw there is the so-called “canine fossa” - a depression next to the infraorbital foramen through which the infraorbital nerve and artery pass. The anterior part smoothly transitions into the outer part; its medial border is the nasal notch.

The upper jaw has a tubercle, which is located on the infratemporal surface. It is separated from the anterior zygomatic process. This part is often convex. It contains small alveolar openings that lead into the alveolar canals.

In the body of the upper jaw there is an airway - the maxillary sinus, which opens into the nasal cavity. It is covered with a mucous membrane. Its bottom is located next to the apexes of the roots of the following teeth: the first and second molars, as well as the second premolar. On the nasal surface is the crest of the inferior turbinate.

Chewing muscles.

The frontal process connects to the frontal bone, and the attachment point of the turbinate is marked by a ridge on the medial surface. The palatine groove runs along the nasal surface, which is the wall of the palatine canal.

The nasal surface passes into the superior one with the right and left palatine processes. They, in turn, unite at the anterior part of the hard palate, forming the floor of the nasal cavity and the skeleton of the palate. The nasal surface also has an opening for communication between the nasal cavity and the maxillary sinus.

The zygomatic process connects to the zygomatic bone, forming with it a thick support, which bears the load during chewing.

The maxilla also includes the orbital, or upper, surface. It is the lower wall of the orbital orbit. From the outside, it smoothly passes into the zygomatic process. The infraorbital margin connects with the frontal process, along which the lacrimal crest runs.

Orbital orbit.

On the medial edge is the lacrimal notch. It includes the lacrimal ossicle. Near the posterior edge of the orbital surface of the upper jaw, the infraorbital groove originates. The posterior and inferior margins form the orbital fissure, which contains the infraorbital groove. In the forward direction, it gradually passes into the infraorbital canal. Describing an arc, it opens at the front.

The outer-lateral surface is turned towards the pterygopalatine and infratemporal fossa. In the posterior lower area there is a tubercle of the upper jaw. This part is dotted with small holes through which nerves and blood vessels pass to the teeth.

The upper jaw is formed from light thin plates that limit the airways. Inside the body there is the largest among the accessory parts - the air cavity. Along with this airiness, human anatomy is also designed for high loads. Therefore, buttresses are formed on thin plates - denser areas that provide bone strength.

Anatomy of the lower jaw

The structure of the lower jaw includes a body and two processes (branches). Unlike the upper one, the largest arch in it is basal, and the smallest is dental. The body consists of two halves: the base and the alveolar part. In the first year of life they unite into one bone. The height of each half is greater than the thickness.

The chewing muscles are attached to its surface, so there are many bumpy areas and roughness on it. This is the only part of the facial skull that has the ability to move.

On the outer surface of the lower jaw there is a chin protrusion. Outside of it protrudes the mental tubercle, on top and outside of which is the mental foramen. It corresponds to the placement of the roots of the second small teeth. From behind this hole, an oblique line is directed upward, which becomes the leading edge of the branch. It contains the alveolar elevations.

On the alveolar arch, the anatomy provides sixteen alveoli for teeth. They are separated from each other by interalveolar septa.

Alveoli for teeth.

On the inner surface of the body, the lower jaw has a mental spine. It can be either single or bifurcated. On the lower edge is the digastric fossa, where the digastric muscle is attached. In the lateral areas there are mylohyoid lines. The sublingual fossa is attached above it, and the submandibular fossa is attached a little lower.

The lower jaw is also “equipped” with a hole and a certain limitation - a tongue. Deep into the hole in the thickness of the spongy substance there is a canal with blood vessels and nerves. On the surface it exits through the mental foramen. The maxillary-hyoid groove runs from it, and a little higher - the mandibular ridge.

On the outer side there is a chewing tuberosity, which occupies a position in the corner. On the inner part of the masticatory tuberosity there is a pterygoid tuberosity. The medial pterygoid muscle is attached to it. The hyoid groove runs down and forward along the pterygoid tuberosity.

Sometimes it turns into a canal, covered with a bone plate. The mental protuberance is located on the external tuberosity in the symphysis area. This part fuses with the bones of the chin, which participate in the formation of this protrusion. On the side of it is the mental foramen, through which the mental nerves and vessels exit.

At the upper end of the branch there are two processes: coronoid and posterior. The temporalis muscle is attached to the coronoid, and the posterior one ends with a head, which has an articular surface in the form of an ellipse. It is involved in the formation of the temporomandibular joint.

The lower jaw consists of copacta bone. It belongs to the unpaired type and has the ability to move in both the vertical and horizontal planes due to the anatomy of this joint.

Structure of the temporomandibular joint

The lower jaw, with its head and articular tubercle, as well as the scaly part, forms the temporomandibular joint. The axes of the roller-shaped heads converge in front of the occipital foramen. The fossa consists of two parts: intracapsular and extracapsular. The first is located in front of the stony-squamous fissure, and the second is behind it.

The first, as its name suggests, is enclosed in a capsule. It extends to the tubercle of the joint and reaches its anterior edge. The surface of the temporal joint is covered with connective cartilage, and in its cavity there is an articular disc - a fibrous cartilage plate.

The anatomy of the temporomandibular joint has the following ligaments:

• lateral;
• medial.

The lateral ligament begins at the base of the zygomatic process. Next, it is directed to the posterior and outer surface of the neck of the lower jaw. Some of the bundles are located in the capsule of the temporomandibular joint. The medial ligament begins near the inner edge of the articular surface and runs along the ventral surface.

There are also ligaments that are not associated with the capsule, but belong to the temporomandibular joint: the styloid and sphenomandibular ligament.

The upper surface of the temporomandibular joint disc is adjacent to the articular tubercle, and the lower surface is adjacent to the head of the mandible. It divides the joint into two sections, each cavity of which is lined with an upper and lower synovial membrane. The tendon bundles of the lateral pterygoid muscle are attached to the inner edge of the disc.

The temporomandibular joint is a locking joint. Thanks to its movements, it is possible to raise and lower, extend and move the lower jaw of a person.