Jaw: Anatomy of the upper and lower jaw apparatus

Understanding the structure of the human body is very important in the treatment of various diseases. In particular, the anatomy of the jaw apparatus directly affects the actions of the dentist.

The structure of the skull is very complex. Each part has its own meaning and distinctive characteristics.

Due to the individual shape, the external appearance of a person changes, the jaws serve as the basis for the formation of the sense organs, thanks to them we have the opportunity to eat and talk.

General information

The jaw is one of the most complex bone and joint structures in the body. Due to their structure, they can perform certain functions in the process of human life, they are able to withstand heavy loads.

The upper is the fixed part of the skull, which serves as the basis for the creation of the nasal cavity. The lower one has the ability to move, and is attached to the skull using the temporomandibular joint. It is interesting that until the child reaches the age of one year, it consists of two separate halves and grows together in the process of growing up.

The jaw apparatus has a number of important functions. Its lower part is under heavy stress, therefore it is subject to great damage. At the same time, oral hygiene is carried out better on it than on the upper one. This is due to the poor visibility of the second.

Each person has their own unique differences in the structure of the jaw apparatus, which affect the appearance of the individual. With age, its structure changes, resulting in changes in appearance.

Functions

The complex structure of this part of the body affects not only the appearance, but also allows it to perform a number of functions, without which human existence would be difficult.

Main functions:

1. Biting, chewing food: thanks to the teeth attached to the jaw, we can eat food, grind it into small pieces for further digestion. The jaw apparatus can withstand a lot of stress, which allows you to chew hard and tough food.
2. Swallowing: helps to move food in the mouth, swallow it.
3. Conversational speech: the movable jaw part of the skull allows you to make sounds, communicate with people around you. Diction becomes difficult if damaged or improperly structured.
4. Breathing: they are not directly involved in the breathing process, but with injuries it is much more difficult to inhale or exhale.
5. Fixation of teeth.
6. Formation of cavities for the senses.

All functions play an important role in normal life. When certain violations occur in their structure, a person experiences difficulties and needs help.

The structure of the upper jaw

It has two paired bones and represents the largest part of the skull. Its structure is very different from the lower one. All bones on the front of the skull are connected to this part of the jaw apparatus.

It forms the main features of the face and cavities for the sensory organs:

• the walls of the eye sockets;
• oral cavity, nose;
• temporal fossa;
• pterygoid fossa of the sky.

The upper part is comparatively large in size, but at the same time has a low weight. This is due to the presence of cavities in it. The body and processes are distinguished in the structure.

The blood supply is due to the maxillary artery and its branches. It diverges into the vessels supplying the teeth and alveolar processes, palate and cheeks. Innervation is provided by the trigeminal nerve, namely, its maxillary branch.

The structure of the skull. Video:

The main element of the jaws is the body. It contains the airway sinus, called the maxillary sinus. It is covered with a mucous membrane and is the largest sinus around the nose, in the shape of a pyramid.

Five walls are distinguished on the sinus - upper, medial, anterolateral, posterolateral, and lower. Several pockets form in it, in which pus can accumulate. From here the sinusitis disease takes its name.

Four bony processes extend from the body.

All of them are directed in a certain direction and carry a certain meaning:

1. Alveolar rushes down. It has two walls and consists of a spongy substance. One wall is located outside and is called buccal, the second (called lingual) is placed inside. Alveoli are located in the spongy substance, intended for the base and fastening of the teeth. The process resembles a bone ridge, which bends in an arc with an external bulge.
2. The palatine forms the bony palate, directed medially. It looks like a thin bone plate with a horizontal direction. The lower surface contains grooves and small depressions where the salivary glands pass. The upper part flows into the nasal cavity. Its plane is very smooth. This process separates the cavity of the nose and mouth.
   

   1 - dental alveoli; 2 - palatine process; 3 - zygomatic; 4 - the median palatine suture; 5 - interalveolar septa

3. The zygomatic is directed laterally. Its main task is to redistribute the load when chewing food and redirect it to the zygomatic bone. This is due to the zygomatic alveolar ridge. It is located in the middle of the bottom edge and the alveolus of the first molar.
   

   1 - frontal, processus frontalis; 2 - front surface, facies anterior

4. The forehead is directed upwards. From below, it flows into the body, the anterior edge converges with the nasal bone, and the posterior edge with the lacrimal bone. From above it grows together with the frontal bone.

In the structure of the body, the following surfaces are delimited:

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

They all have a characteristic shape and perform certain functions.

The front has a concave shape. In its lower part, the alveolar process originates. Above, an infraorbital margin is formed with an opening, where the facial nerve endings and blood vessels fit. It is here that anesthesia is performed for complex dental operations.

Just below the opening under the eye socket is the canine or canine fossa, where the muscle responsible for lifting the corners of the mouth begins. The anterior and orbital surfaces are separated by the infraorbital region. The nasal notch serves as a septum and contributes to the formation of the nasal cavity.

The orbital surface is very smooth and has the shape of a triangle. With its help, the lower wall of the orbit is formed. Forms the infraorbital margin in front. From the outside, it flows into the zygomatic process, and in the middle into the lacrimal crest. The posterior edge provides the basis for the infraorbital sulcus, which then flows into the corresponding canal and the opening in the canine fossa. Participates in the formation of the gap of the eye sockets.

The infratemporal forms elevations, which are also called tubercles. Holes are located on the tubercles, where canals run with branches of nerves and blood vessels to the large molars. It is in this place that anesthesia is placed when removing molars.

In the medial direction from the foramen is the pterygo-palatine groove, which forms the anterior wall of the canal of the same name. The infratemporal and anterior surfaces are separated using the zygomatic ridge.

The nasal surface participates in the formation of the lateral wall of the nasal cavity. Above, in the posterior corner, there is a hole in the maxillary sinus and a lacrimal groove. The concha ridge is located on the bottom of the front side, where the inferior concha of the nose is fixed.

The bottom of the plane flows smoothly into the process of the nose, which connects the lower passage of the nose and the orbit. Behind the maxillary sinus is the palatine groove, which forms the large palatine canal. It is here that pus accumulates and the inflammatory process begins with sinusitis.

Teeth

Each jaw has 14 to 16 teeth. They all have their own characteristic structure and perform certain functions:

1. Central incisors have a slightly flattened and elongated crown. On the side of the incisal edge, there are three tubercles. The incisors are held by one long root. The main function is to bite off food.
2. The lateral incisors have a similar structure to the central ones, but smaller. They also participate in the biting process.
3. Canines have a convex, tapered crown. The incisal edge is pointed and has one tubercle. The function is nibbling.
4. Premolars includes two teeth on the left and right sides between the canines and the first molars. The first pair has a similar structure with canines, the second pair with molars. They can have from one to three roots. Functions include nibbling and grinding food.
5. The first molars have a rectangular crown with a wide chewing surface. Attached with three roots - two buccal, one palatine. The main function is to grind food.
6. Second molars have a similar structure to the first, but smaller. The differences also lie in the location of the fissures.
7. Still others are called wisdom teeth. In some cases, they may not cut through at all. They can have twisted roots of different numbers.

Age features of development

The buds are laid at the stage of embryo development. In the process of its intrauterine growth and development, bones gradually grow together and teeth emerge.

In newborn babies, the upper jaw is still poorly developed. It consists mainly of a scion. Further development is uneven. The main formation takes place during teething and ends at about 16 years old, when the main bite is formed.

Bones increase in size with age. Both halves are fused together with a strong seam, the planes acquire the basic shape. The hard sky becomes domed.

With the onset of aging, changes occur in the jaw apparatus. With the loss of teeth, the processes atrophy and descend, the hard palate becomes flat.

Lower anatomy

The structure of the lower part of the skull is significantly different from the upper one. This part is one piece and has a horseshoe shape. Only she in the structure of the skull has the ability to move.

The structure of the skull. Video:

The structure of the body is subdivided into the base or lower part and the alveolar part, in which the teeth are located.

The body has a curved shape, outside it is convex, and the inside is concave. The connection of the right and left parts of the body occurs at an angle, which determines the distinctive features of a person. This connection is called the basal arch.

The body height is not the same over the entire plane. The highest place is in the region of the canines, the lowest is in the region of the third molars. The thickness is also not uniform. The thickest part is in the area of ​​the molars, and the least is near the premolars.

The number and location of dental roots determine the cross-sections. For the anterior teeth, the sections have a triangular shape with apex downwards, and for molars, on the contrary, with apex upwards.

The two branches (branches) are important parts. They diverge upward at an obtuse angle. There are two edges on each branch - in front and behind, as well as two surfaces - inner and outer.

The surfaces of each branch flow into two special processes - the coronal and condylar. The first is necessary to fix the temporal muscle, and the second serves as the base of the joint connecting the cheekbones.

The outer side of the branches is curved, in the middle it forms a buccal crest, where the muscles of the cheeks are attached. This surface also creates the jaw angle where the masseter muscle is attached. The inner surface flows smoothly into the body.

Inside the branches in the region of the jaw angle, the median pterygoid muscle is attached and there is an opening, which is covered by a bony protrusion called the uvula. A little above this hole, the jaw ligaments are attached.

The gaps between the branches are different for all people and determine the main features of the face.

In the structure of the body, the inner and outer surfaces are also distinguished. In the center of the outer is the chin protrusion. It serves as a hallmark of today's human image and serves as the basis for shaping the chin. The chin tubercles with holes are located on both sides of the protrusion. Nerve fibers and blood vessels run along them.

On the inner surface of the jaw body there is a bony spine called the chin spine. This is where the hypoglossal and lingual muscles come out. Below the thorn is the digastric fossa, where the muscle of the same name originates. On the back of the surface is the jaw-hyoid line, where the bases of the muscles and the grooves for the salivary glands are located.

Teeth position

A person's bottom has the same number of teeth as above. Their name and function are the same.

The central incisor is the smallest of all teeth. The lateral incisor and canines are slightly larger, but still smaller than the upper counterparts.

The lower molars and premolars differ from the upper ones by the presence of tubercles and roots.

The teeth are located in their individual alveoli, which provide reliable attachment and allow them to withstand heavy loads during the process of chewing food.

In children

The lower jaw in childhood is about the same as in adults, but differs in some features. In newborns, it consists of two halves, between which connective tissue is located. Complete bone fusion occurs only by 1-2 years.

In children, this part of the skull is represented mainly by a process, the jaw body occupies less than half of the total volume. Thanks to this, the body quickly adapts to teething.

The alveolar processes grow only until the age of 3 years. Further, only their lengthening occurs. With the growth of a person, the mandibular body can increase almost 4 times.

The branches are underdeveloped. With the growth of the child, they expand and change the angle of inclination. The floor of the oral cavity is shallow, with mild folds. The channel is almost straight and runs close to the edge.

The bite is formed in several stages:

1. Temporary or milk bite.
2. Changeable bite - widening the distance between teeth before changing them.
3. Permanent is formed after the change of teeth.

Other structural features

A large number of muscles join the jaw. Thanks to them, a person can bite and chew food, talk and breathe through the mouth.

The blood supply is carried out using the jaw artery and its branches. The blood outflow is carried out through the posterior-maxillary and facial veins. There are also lymph nodes - submandibular and submental. Many tumor processes can arise in them.

The trigeminal nerve is responsible for innervation, namely, its second and third branches.

Developmental pathologies

In the process of intrauterine development of the embryo, the foundations of the jaw apparatus are laid, with various violations, certain deviations from the norm may occur. But even during childbirth and later growing up, there is a risk of developing pathologies as a result of trauma, inflammatory processes and other external influences.

Each anomaly affects the person's appearance and the functional ability of the jaws.

Pathology:

1. Congenital jaw clefts occur due to failures of embryonic development. Most often, clefts of the palate, upper and lower lips are observed. Therapy consists of surgery and cleft suturing.
2. Microgenia - insufficient formation of the lower part. It can be symmetrical or asymmetrical. In this case, the lower part of the face is reduced and can be shifted in the direction of the lesion or back. Occurs after previous illnesses.
3. Macrogenyor progeny - excessive formation of the lower part. The lower part of the face is massive and protrudes significantly forward. It is mainly a hereditary predisposition.
4. Prognathia - strong development and protrusion of the anterior part of the upper jaw with the normal formation of the lower. The cause is heredity or malocclusion.
5. Micrognathia - insufficient formation of the upper part. The reason may be trauma, surgery to remove clefts.
6. Open bite - pathology, when only the molars are connected when the teeth are closed, there is a gap between the rest. The reason may be rickets, fracture of the skull bones, surgery.

Treatment of these pathologies is carried out by orthodontists, for example, with the help of braces. The therapy can be carried out after the completion of the formation of the facial skeleton, after about 17 years.

Treatment with plastic surgery is possible. Such operations are performed to correct the shape of the bones or soft tissues of the face. Implants can be used.

The jaw apparatus is an important and complex organ of the human body. Its anatomy affects not only health, but also the aesthetic appearance of the face. It performs important functions in the nutrition and communication of people.

With the growth of a person, the jaw undergoes certain changes. Often there are developmental pathologies that change the appearance of a person. Any disease requires the help of a doctor and certain treatment.