Do all fish have teeth? Evolution of the dentition and oral glands of vertebrates

A tooth is an organ oral cavity, consisting of elements such as crown, neck and root. Several dental cavities have their own unique biochemical composition, shape, and differ between a child and an adult. Each element of the dentition is responsible for proper chewing, diction, and facial shape. Most of the tooth is occupied by dentin, covered with enamel and cement; the organ has its own nervous apparatus, lymphatic and blood vessels. An adult normally has from 28 to 32 teeth, while a child has 20 teeth in a primary dentition. Each person's teeth are different, their shape is different, they have a unique slope, but the pattern of eruption never changes.

Previously, the tooth structure of a child and an adult was very different. Modern dentistry will never see conical incisors in a healthy person. Over time, the pattern of the dentition, chewing coefficients and many other characteristics have changed, which is associated with changes in nutrition.

What is a tooth?

An ideal dentition with straight teeth on the bottom and upper jaw does not exist, the shape of the incisors and canines is different, which gives the uniqueness of the dentition of each adult and child. The roots of each organ are also different; chewers may have three or four, while the third molar on the upper and lower jaws may have up to five. The absence of this crown, that is, a wisdom tooth, is normal; it can erupt up to 40 years. Inside the cavities, each organ of the dentition has connective tissue, which is permeated blood vessels and nerves, which is defined as the pulp.

First, a person’s primary or temporary bite erupts, which has 8 molars, 8 incisors and 4 canines, there are 20 in total. The permanent bite in an adult consists of 8 premolars, 8 incisors, 4 canines and 12 molars

The milk bite begins to erupt as early as six months; at three years the last ones are already present. temporary crowns, and from 5 to 13 years the temporary bite changes to permanent. During the period of change of bite, one can observe such an anomaly as supernumerary teeth when there is primary and permanent dentition. In dentistry, this is most often observed in the incisor area.

The organ on the upper and lower jaw has three main elements:

the root is not visible part tooth, is located in the recess of the jaw and performs the function of holding the tooth in the bone;
the neck is the intermediate part between the crown and the root of the tooth, normally it is located in the marginal region of the gums, where the enamel ends, the appearance carious cavities and other pathologies can lead to its exposure;
the crown is the already visible part, which is most often susceptible to the formation of carious cavities and other pathologies;
The ligamentous apparatus of the tooth on the upper and lower jaw consists of connective fibers that support the root and neck of the tooth; the jaw in the neck area has a horizontal direction and forms a circular ligament of the organ with the gum.

Composition of tooth cavities

The organ has three main types of tissue: cementum, dentin and enamel.

Dentin is collagen impregnated with mineral salts, which gives it strength. The tissue is penetrated by thin tubules in which odontoblasts are located, ensuring the growth and development of the tooth. This is a living tissue in which constant metabolic processes.

The composition of enamel is inorganic substances; its strength is close to diamond. Also, its composition is represented by enamel prisms, which are responsible for strength, and it is covered with enamel skin.

The pulp or, as it is also called, the nerve has next lineup at the incisors, chewing teeth and fangs:

Odontoblasts are present on the surface of dental cavities and penetrate into the dentin tubules, which allows metabolic processes to occur in such a strong organ;
Blood vessels and lymphatic vessels, which provide nutrition and protection to the tooth;
Nerve processes that are responsible for the sensitivity of all organ cavities.

This is the most sensitive part and has many functions including protection and repair. Cluster large quantities nerve endings and blood vessels leads to strong pain syndrome in case of an inflammatory process.

Cement covers the root of the tooth, like enamel covers a crown, and its main function is to hold ligamentous apparatus. Its composition is close to bone tissue person.

Biochemical composition

In a child and an adult, each organ of the dentition on the upper and lower jaw consists of calcified tissue, and the main one is dentin, covered with enamel. Each part of the tooth is different in composition; they have a unique functional purpose and biochemical composition. The main components include minerals, inorganic compounds, organic compounds and water.

Wet mass percentage:

enamel consists of 2.3% water, dentin 13.2%, pulp 30%, cement 36%;
1.7% enamel consists of organic compounds, 18.5% dentin, 39% pulp, 21% cement;
enamel consists of 96% inorganic compounds, dentin 69%, pulp 25%, cement 42%.

The basis of the dry mass is calcium; the tissue also contains magnesium, phosphorus, potassium, sodium and other trace elements. Organic compound teeth are organic acids, proteins, hormones, lipids, enzymes, vitamins, nucleic acids.

The main part is soluble and insoluble proteins. Soluble ones perform mainly protective, thermal, transport and other functions. Largest quantity globulin and albumin are concentrated in the pulp, and it also contains glycolytic enzymes and tricarboxylic acids. The main soluble enzymes in pulp are acidic and alkaline phosphatase, they are the ones who take part in the direct mineral metabolism of organ tissues.

Shape of crowns in children and adults

Forms masticatory organs, canines, and incisors are different because they perform different functions. In fish, for example, they are conical in shape, which allows them to hunt, but in humans everything is arranged differently.

The anterior group of teeth are chisel-shaped incisors; they are necessary for cutting and grasping food. Behind the incisors there are cone-shaped canines; they, like the incisors, are single-rooted. In this area, the structure of the tooth most often changes and anomalies appear in the form of conical crowns. The fangs are wedge-shaped, have a convex front surface, they have a tubercle on the cutting part, which gives the organ a specific shape.

The next organ on the upper and lower jaw will be the first molar, which is prismatic in shape with a convex lingual and buccal surface. The roots of the first molars are bifurcated and located on the buccal and lingual sides.

The second premolar on the upper and lower jaws has a similar shape, but its buccal surface is larger. The roots of the second premolars are cone-shaped. Then comes the largest tooth in the jaw - the first molar, the molar. The shape of its crown is rectangular, the chewing surface is diamond-shaped, and has four tubercles that are responsible for chewing. It has three roots, they are straight, divided into two buccal and one palatal.

Features of the dentition in humans and animals

The structure of a tooth of the simplest conical shape modern dentistry will never see again. The standard structure of the dentition in a child and an adult on the upper and lower jaw differs significantly from the cavities of some animals. Almost all types of animals need protection and attack, which is why they have conical crowns, the absence of incisors characteristic of humans, and tusks to this day. In fish, in addition to conical teeth, the dentition is also present in the pharynx.

Predators have conical crowns and the presence of sharp incisors on the upper and lower jaws, as well as the special composition of the cavities, which ensures good tearing of food, especially raw meat.

In humans, the roots of the dentition are weaker, anatomical structure teeth are adapted to survive predominantly soft food. Straight roots on the lower and upper jaw, the presence sensitive cavities, the absence of conical organs no longer makes it possible to tear food apart. Anomalies of form are not excluded today, and abnormal organs conical shapes can become a problem for humans.

Dental treatment – modern dentistry

Dentistry is divided into several areas, each section deals with individual dental problems in adults and children.

Description of areas in dentistry:

pediatric dentistry – studies the structure of the child’s primary occlusion tooth;
therapeutic dentistry – deals with the treatment of hard dental tissues;
surgical dentistry - studies the structure of the tooth and its root part, removes crowns and roots, treats stones in salivary glands, maxillofacial plastic surgery;
orthopedic dentistry – deals with the correction of the shape and position of the dentition in children and adults;
aesthetic dentistry – makes the smile attractive, corrects complex defects (extraordinary conical crowns, abrasion of enamel, discoloration of the dentition);
orthodontic dentistry – deals with the correction of dental malocclusion and eliminates aesthetic problems.

Dentistry pursues three main goals - maintaining the integrity of the jaw row, improving aesthetics and restoring chewing function.

The process of digestion is carried out by the digestive organs. The digestive tract begins with the oral opening and ends with the anal opening. In lampreys and hagfishes it is represented by a tube of more or less the same diameter, but in real fish it is usually differentiated into sections: oral cavity, pharynx, esophagus, stomach, intestines (Fig. 12).

Fish have an upper, lower and terminal mouth. The position of the mouth depends on the methods of obtaining food. In some cases, this general dependence is violated due to the predominant development of other groups of adaptations.

Teeth in the oral cavity can be of various shapes - pointed, fang-shaped, awl-shaped, flattened in the form of plates. It is characteristic that they can be located on various bones of the oral cavity: jaws, vomer, palatine bones, etc. Some peaceful fish may have no teeth. Carp fish (bream, roach, carp, etc.) do not have teeth in the oral cavity, but have so-called pharyngeal teeth, which are placed on modified fifth gill arches. The purpose of teeth is to hold trapped food or crush it. In cyclostomes (lamreys, hagfishes), the teeth are represented by keratinized epithelium, very hard, easily cutting through the walls of the fish’s body. In real fish, the structure of teeth is more complex. They resemble the teeth of mammals. The tooth has an outer enamel layer, under it a layer of dentin and inside a connective tissue papilla with nerves and blood vessels that supply the tooth. Fish teeth usually do not have roots. Fish teeth are replaced throughout life.

Throat - area digestive tract between the oral cavity and the esophagus. The pharynx has gill slits connecting the gill cavity to the pharynx. The partitions of the slits are formed by gill arches bearing gill rakers and petals. Gill filaments are a respiratory organ. Gill rakers serve as filters. The number, character and height of the stamens correspond to the feeding method of the fish. In predatory fish, gill rakers are usually sparse and short. They protect the petals from damage by large food. In fish that feed on plankton (small organisms suspended in the water column), the stamens are thick and long; they are a filtering apparatus that filters out plankton. The pharynx passes into the esophagus.

The esophagus is a tube whose walls are formed smooth muscles. Its purpose is to carry food into the stomach. The esophagus does not have digestive glands. In predatory fish, the stomach usually has the shape of a siphon (peaceful fish that feed on plants or small animals may not have a stomach). The walls of the stomach secrete pepsin and hydrochloric acid. Digestion begins in the stomach. Pepsin in the presence of hydrochloric acid decomposes food proteins into peptones. Fats and carbohydrates do not decompose in the stomach. The intestine is divided into three parts: the foregut, midgut and hindgut. Surface inner wall folded intestines. The folds increase the surface of the intestines and thereby contribute to a better effect of digestive juices on food. The ducts of the pancreas and liver flow into the foregut. In some fish, for example, herring, salmon, mackerel, the foregut has special blind appendages called pyloric. They are needed to increase the absorption surface of the intestine. The pyogenic appendages contain enzymes that break down protein, carbohydrates, and fats. Sharks, rays, sturgeons, and lungfish have a spiral valve (a spirally arranged fold) in the middle part of the intestine, which also increases the absorption surface of the intestine. The hindgut opens either with a separate opening called the anus, or with a special extension - the cloaca (in cartilaginous and lungfishes). The length of the digestive tract depends on the feeding habits of the fish. Predatory fish have a short digestive tract, peaceful fish have a longer one (Fig. 13).

Pancreas. Histological studies It was found that the pancreas in fish is fused with the liver. Macroscopically it is indistinguishable. The pancreas secretes enzymes that break down protein, carbohydrates and fats.

Liver. The liver, as a gland, performs several functions. In some fish (for example, cod), fat reserves are deposited in the liver, and carbohydrate reserves in the form of glycogen are deposited in the liver of all fish. Moreover, the blood digestive organs First of all, it passes through the liver, where foreign proteins are neutralized. Among the substances coming from the digestive tract into the blood, there are often toxic substances- indole, skatole, etc. In the liver they combine with other substances, such as acids, and become harmless to the body ( barrier function liver). The liver produces bile, which is collected in gallbladder, and then flows through the bile duct into the digestive tract. Bile emulsifies fats and activates intestinal enzymes.

The presence of teeth, according to biologists involved in evolutionary problems, is one of the main reasons for the successful development of all vertebrates. Thanks to jaws studded with teeth, living creatures conquered the ancient seas and eventually moved to land. Fish, like the first animals in general, did not develop teeth right away.

Along the edges jaw bones Sharp, hard cones began to grow, which made it possible to better hold prey. This advantage soon became decisive for survival, and gradually the oral instrument became larger and stronger. Over time, tools emerged to chop, crush, or even grind food.

Modern fish have wide range functions made possible by teeth.

Sharp grips

In many predatory fish, even after hundreds of millions of years, the original function of the teeth can still be observed. For example, the jaw of a pike is studded with hundreds of needle-sharp cones. With them, she firmly holds the prey until it is swallowed.

Fish with such teeth can, however, only eat food that passes uncrushed through their pharynx.

Sharp teeth, which make it possible to divide prey into “portions,” are not found in the fish of our reservoirs. Maybe fortunately. But sharp cutting teeth are still created by nature. They are found, for example, in many sharks, blue fish and piranha. Some sharks are capable of tearing small pieces of meat from the bodies of large marine mammals such as seals and whales.

Brush and pharyngeal teeth

A widespread type of teeth are the so-called “brush” teeth, which are found in perch, burbot and catfish. These are areas with small and even tiny hook-shaped needles that form a rough surface with which it is possible to firmly hold prey.

Fish with this type of teeth have adapted to hunt by sucking in water and food through their wide-open mouth. Large long teeth they would only get in the way when sucking in prey.

The pharyngeal teeth of carp fish have an unusual shape. It is characteristic of each species and allows one to clearly identify closely related fish. These teeth are used to crush plants and crush hard-shelled prey such as clams and crayfish.

In many predatory fish, not only the jaws, but the entire oral cavity are equipped with teeth. There are teeth on the plates of the palate, on the gill arches and on the tongue.

In salmonids, the toothed palate, especially the so-called false bone, is a reliable method of identifying the species.

What makes fish teeth hard?

The fish tooth is made from the bone-like material dentin and has the shape of a cone, which is covered with an unusually tough layer - tooth enamel.

Tooth enamel consists of wear-resistant calcium phosphate (apatite). It has been preserved for millions of years rocks, therefore, the teeth of long-extinct ancient fish remain well preserved.

Changing teeth

In fish, in contrast to humans, there is permanent shift teeth.

Worn teeth fall out and are replaced with new ones. This replacement occurs until the end of the fish’s life.
The jaws are strewn with teeth of various ages and precisely the type that always provides the function of biting. A predatory fish without teeth would have difficulty holding onto prey and would not be able to continue its race, as it would die of starvation.

Thus, the evolution of any fish favors its teeth changing. The common belief that pike renew their teeth in the summer and therefore do not eat anything is a fairy tale.

Daniel Luther (Fish with us 8/2011)

They may be associated not only with a deviation in their position, but also with their irregular shape. One of the pathologies of the shape of teeth is their narrowing: conical and awl-shaped (in the form of a screwdriver). Teeth like this acute form are extremely rare - one case per thousand people.

Contrary to the erroneous opinion of some Patients, this is not only an aesthetic problem, but also a serious pathology that can seriously damage soft fabrics oral cavity. In addition, this form of teeth can lead to disruption of chewing function, as well as cause increased abrasion of the enamel and sensitivity of the teeth.

This anomaly is characterized by several signs:

sharpening of the teeth to the cutting part, their conical or barrel-shaped shape;
the presence of the same slope on all sides;
smaller size compared to other teeth;
Predominant location on the upper jaw.

Causes of conical and awl-shaped teeth

The formation of conical and awl-shaped teeth may be due to for the following reasons:

genetic changes that lead not only to a change in shape, but also to over-equipment of teeth;
incorrect formation of the primordium plate, leading to its splitting;
infectious and inflammatory diseases, causing disruption metabolism in the human body;
vitamin D deficiency, which has significant influence per condition skeletal system person;
prematurity of the child or his dystrophy;
maternal illnesses suffered during pregnancy.

Types of conical teeth

There are the following types of conical teeth, differing from each other in clinical signs:

spine-shaped: the crown part of such teeth is characterized by a narrowed shape resembling a spike. As a rule, they are formed as rudiments of the upper lateral incisors. The main reason the spiky shape of the teeth is due to ectodermal dysplasia or the presence of a cleft of the upper palate;
Hutchinson's teeth: have a barrel shape. They are characterized by the presence of a small notch on the cutting part in the form of a semicircle. It usually occurs due to a disease suffered by the child’s mother during pregnancy: most often, rubella or syphilis;
Pflueger teeth: have the shape of an unopened bud, often covered with microdefects in the form of dots, pits and horizontal grooves. Usually these are premolars.

Treatment methods

Fortunately, modern orthodontics allows not only to identify the presence of pathology on early stage, but also completely correct the shape of the teeth.

Treatment methods for narrowed teeth include:

prosthetics using metal-ceramic crowns. This material allows you to fully convey the color and structure of tooth enamel, which is why it is very popular. However, its use requires significant preliminary preparation of dental tissue;
The application of veneers is a construction of thin ceramic plates that are fixed on the outer surface of the teeth. The main advantage of this method is minimal preparation of dental tissues;
composite restoration. This method is much more affordable in cost than veneers and consists of layer-by-layer application of a light-curing composite;
removal of teeth followed by prosthetics. Most radical method. Used when teeth are abnormal in size.

In general, cone-shaped teeth respond well to treatment, regardless of their size or type.