Are there any animals whose teeth can regenerate?

Let's talk about how animals' teeth regenerate. First, there is ectodermal mesenchymal tissue in the primitive notch of early embryos to induce epithelial proliferation and form primary epithelial cords. Reptiles, mammals, some amphibians and some fish appear at specific points in the maxillary and mandibular arches. Some fish and amphibians may appear in the lower jaw.

Primary epithelial cord can be divided into vestibular plate, vestibular plate and dental plate.

. The vestibular plate develops into vestibular sulcus, and then the tooth plate will form tooth germ. The position of the dental plate determines the position of the teeth in the future. The dental plate is guided by the local mesenchymal tissue to develop into teeth with different shapes (only mammals and reptiles have tooth differentiation).

When the first batch of teeth erupt, the dental plate will proliferate to the lingual side and root of the inherited teeth.

Continuous thin layer

In the future, new teeth can be formed to replace old teeth (only once in mammals). But the two sides near the distal end (the jaw arch where the free end has no teeth) proliferate and form.

Hyperplastic dental plate attachment plate

Forming new teeth, such as permanent molars (permanent cracked teeth) in mammals.

(hereditary teeth and hereditary teeth)

The classification of teeth can be divided into:

① End tooth: the tooth is located at the upper end of the jaw, which is not closely connected with the jaw and has no obvious root. (such as fish and amphibians)

② Lateral teeth: located on the lingual or palatal side of the jaw, partially connected with the jaw, with incomplete root evolution. (Like most reptiles)

③ Alveolar teeth: located in the jaw, and the root is closely connected with the jaw through periodontal ligament. (such as dinosaurs, crocodiles, mammals)

Classification of tooth morphology

Homomorphic teeth: teeth are basically the same shape, such as single vertebral teeth of living reptiles and dinosaurs.

Tooth abnormality: Tooth shape varies with position and function, such as mammals and mammal-like reptiles. There are several special cases of irregular teeth:

① High crown teeth: common in ruminants and herbivores. Used for repeated grinding.

② Tooth fracture: specialization of the last maxillary premolar and the first mandibular molar of carnivores. Used to tear food.

The change of teeth gives birth to all kinds of animals, as long as they have real teeth. Tooth: specialized hard tissue owned by most vertebrates for chewing or tearing food) has the ability of replacement. The number of replacements is determined by the number of developable dental plates:

Most mammals have two sets of teeth: permanent dentition and deciduous dentition, which is mainly due to the growth and development of jaws.

However, the existing dentition of reptiles, fish and amphibians are mostly multi-dentition that can be replaced for life.

(For example, the shark's teeth grow in the middle, and the new teeth move forward to replace the old teeth that have fallen off)

Therefore, bidentate dentition is unique to mammals, while polydentate dentition is very common. Dinosaurs, crocodiles and sharks are particularly famous for their inexhaustible teeth for two reasons:

Because of its huge size, it is convenient for human observation.

② Because they not only have many dentition, but also frequently change from old to new.

Advantages and disadvantages of multi-teeth Many people envy sharks or crocodiles for having teeth that can never be replaced. Knock out the decayed tooth ~ Is your tooth broken? Knock it out ~ Are your teeth loose? Knock it out ~ you can't run out of new teeth anyway. Is that really the case? Let's analyze:

(From top to bottom, sharks, crocodiles, dinosaur teeth)

① Morphology and function of multi-dentition teeth:

The teeth of polydentate animals are isomorphic, so the teeth are basically the same in shape and have similar functions. For example, the teeth of sharks, crocodiles and dinosaurs have only the function of tearing and fixing, and almost no chewing function.

② Root system of multi-fractured teeth:

The teeth of multi-dentition are mostly terminal teeth (sharks) and lateral teeth (most living reptiles), and rarely slotted (dinosaurs, crocodiles). So the roots are underdeveloped. Even crocodiles and dinosaurs with fluted teeth have only one, so the teeth with multiple teeth are not strong.

Therefore, to sum up, the disadvantages of multi-dentition are instability, easy damage and less function. Advantages can be constantly replaced.

Characteristics and advantages of mammals with irregular teeth and double dentition: taking humans as an example. A person has 28-32 permanent teeth and 20 deciduous teeth in his life. Five deciduous teeth with unilateral half jaw in deciduous dentition, namely: I middle deciduous incisor, II side deciduous incisor, III deciduous canine tooth, IV first deciduous molar and V second deciduous molar.

Generally, there are 8 teeth in the unilateral half jaw of permanent dentition, namely: 1 central incisor, 2 lateral incisors, 3 canine teeth (tiger teeth and canine teeth), 4 first premolars, 5 second premolars, 6 first molars (six-year-old teeth), 7 second molars and 8 third molars (wisdom teeth and vertical teeth).

The teeth of human deciduous dentition or permanent dentition are irregular teeth. Front teeth can cut food to help pronunciation, and tusks support squab. Premolars and molars can help canines tear food, and molars chew food. Moreover, the roots of bicuspid teeth are more developed (some teeth are multiple) and stronger. The dental pulp of bicuspid dentition has a powerful restorative function, which can form restorative dentin and resist disease damage even if teeth are worn or decayed.

Conclusion For mammals, bidentate dentition is durable, firm, functional and resource-saving. Compared with the multi-dentition that can only be torn and replaced, winning is not only better. So don't envy many dentition. It is better to use it frequently. Is using a hundred battery cars the same as owning an Audi? !