The histology of the tongue suggests that it is a muscular organ in which the body, tip and root are secreted. The basis is the transverse muscle fibers, going in 3 directions - perpendicular to each other. They enable the language to be mobile in different directions. The muscles are divided into right and left halves by a symmetrically connective tissue septum. On the histology of the tongue, it is evident that muscle fibers alternate within themselves thin layers of fibrous loose connective tissue (PCT). In all this interweaving, blood and lymph vessels, fat cells pass, and ducts of the salivary glands open here. The entire surface of the tongue has a mucous membrane.
Histology of the tongue: the lower surface has an additional submucosal membrane, and the mucous membrane is mobile. The back of the tongue does not have it. And the mucous here is motionless, tightly fused with the muscles.
The histological preparation of the tongue shows that the mucous membrane below is considered to be lining, the dorsal mucosa is specialized. At the border between the muscle thickness and the mucosa itself, there is a network of weave of collagen and elastic fibers - a connective tissue plate. She is quite powerful. Its layer is called mesh. This is nothing but an aponeurosis of the tongue.
In the area of the grooved papillae, it is especially developed. To the edges of the tongue and at the end its thickness is reduced. Histology of the structure of the tongue: muscle fibers pass through the openings of this mesh and attach to small tendons. This makes the aponeurosis even more durable.
Papillae
On the back and side parts in the histology of the tongue, the mucosa forms special outgrowths - papillae. They are distinguished by their shape: filiform, mushroom-shaped, leaf-shaped (only in childhood) and grooved. They have a common structure - based on the outgrowth of the mucosa. Outside they are covered with stratified non-keratinizing squamous epithelium on the basement membrane.
Among the papillae, filiform predominate. They are the smallest, no more than 2.5 mm. According to the histology of the tongue, these papillae are pointed, and their ends are directed towards the pharynx.
The epithelium at their ends is layered, flat, keratinized. He takes part in the formation of plaque in the language. Filiform papillae roughen the tongue. Their purpose is to perform mechanical work, like scrapers. They help move the food lump to the throat. All other papillae are taste buds.
There are no papillae at the root of the tongue. The epithelium is uneven - with fossae and elevations. Elevations are accumulations in the mucosa of the lymph nodes up to 0.5 cm in diameter. Their combination is called lingual tonsil. Depressions, or crypts, are places where the salivary glands (mucous membranes) exit by the ducts.
The structure of the papilla
Any papilla is an outgrowth of the mucosa itself. Its shape is determined by the primary papilla, from which the secondary ones depart. Primary is covered with epithelium, like a crown.
The drug histology of the language:
- Secondary papillae extend from the top of the primary, usually there are 5-20 of them.
- They grow into the epithelium and do not determine the relief.
In the connective tissue of the papillae of the tongue there are many capillaries. They shine through the epithelium, giving the mucosa pink. The histology of the taste buds of the tongue shows that they are located in the thickness of the epithelium of the papillae. These taste buds, or kidneys (gemmaegustatoriae), are the terminal receptors of the taste organ.
They represent groups of spindle-shaped curved cells in an amount of 40-60, among which are receptor cells. They differ in the presence of microvilli at the apical end. The taste bulb is oval in shape. And its apical surfaces are formed in the form of dimples, where the taste pore is located.
Food particles with saliva get here, they are absorbed by a special electron-dense (structureless) substance. These proteins are built into the membrane of microvilli, they are able to change, interact ionic flows. The tip of the tongue responds to sweets, the side surfaces to salty and sour, the root to bitterness.
With this interaction, the potential of the cell membranes changes, and the signal is transmitted to the nerve endings.
Mushroom papillae
Mushroom papillae are few in number and are located on the dorsal surface of the tongue. Most of them are on the sides and at its tip. They are larger, 0.7-1.5 mm in length and about 1 mm in diameter. They got their name due to the fact that their bulk resembles a mushroom with a hat in shape. Each papilla has 3-4 taste buds.
Grooved papillae
Grooved, or grooved, papillae are surrounded by a roller (due to which the name). Localized between the body and the root of the tongue on its dorsal surface. There are from 6 to 12 pieces, stretching along the border line. Their length is 3-6 mm. Above the surface of the tongue rise clearly. In the PCT of the base of the papilla, there are the ends of the ducts of the salivary protein glands, they just open into this gutter. Their secret cleanses by washing the gutter papilla from the microbes that accumulate in it, food particles and desquamated epithelium.
Leaf papillae
Well developed only in children. They are located on the lateral lingual surfaces. Each group consists of 4-8 papillae, between which there are dividing narrow spaces. They are also washed with lingual salivary glands. The length of one papilla is about 2-5 mm.
Language development
The tongue, in fact, is an unpaired outgrowth of the bottom of the oral cavity. It begins at the 4th week of fetal life, when the mesenchyme at the bottom of the primary oral cavity begins to grow (proliferation). The ventral sections of the first three branchial arches participate in this.
The histology of the development of the language in more detail: in the area between the first and second branchial arches, an unpaired lingual tubercle is formed along the midline. From it, the triangular dorsal part of the tongue begins to form.
Two lateral tubercles appear laterally and anterior to this first lingual tubercle from the material of the first arc. They grow very quickly, drawing closer to each other, and soon merge.
In the middle of their confluence, a longitudinal groove remains. It is called the median groove of the tongue. Always visible when examining the oral cavity. In the body of the tongue, the groove continues with a connective tissue septum dividing the tongue into 2 halves. The tip of the tongue and its body originates from these lateral tubercles. They grow together with an unpaired tubercle, cover it. From the mesenchyme behind the blind hole, the root of the tongue is formed. This is the area where the connection of the second and third branchial arches occurs, the so-called bracket.
Upon completion of the development of the tongue, a border between the body and the root appears and there is a V-shaped line with a vertex directed dorsally along which grooved papillae are located. As it grows and develops, the tongue begins to separate from the bottom of the oral cavity, the deep grooves that form it help it in this. They deepen and penetrate under its perimeter. Gradually, mobility also arises in the formed body of the tongue.
The histology of the muscles of the tongue proves that they develop from the processes of the occipital myotomes. Their cells migrate anteriorly. Its complex origin is reflected in its innervation.
Innervation
There are a lot of nervous endings in the language. Due to which there is such an acute pain, if you accidentally bite it. The front of the tongue, 2/3, is innervated by the trigeminal nerve. The posterior third is glossopharyngeal.
The mucous membrane itself has its own nerve plexus, which has nerve fibers in the bulbs of the tongue, glands, epithelium and blood vessels. At birth, his tongue is short and wide, inactive.
Glands of the tongue
They are secretly divided into mucous, protein and mixed. At the root are mucous membranes, in the body are protein, and at the tip are mixed salivary glands.
The ends of their ducts are located between the layers of the PCT in the thickness of the tongue. Protein are next to the grooved and leaf-shaped papillae. The end departments in them are in the form of branched tubes.
Mucous glands are localized on the sides and in the root. Their ends produce mucus. Mixed glands are located in the thickness of the tongue in the anterior region. They have the most ducts.
Language Features:
- mechanical processing of food, mixing and its advancement towards the throat;
- takes part in the production of saliva;
- helps to swallow;
- participates in taste perception.
In a child, the role of the tongue is very important when sucking milk in the first year of life. Another important aspect - language is an organ of articulate speech.