The histology of the tongue suggests that it is a muscular organ in which the body, tip and root are isolated. The basis is transverse muscle fibers running in 3 mutual directions - perpendicular to each other. They allow the tongue to be mobile in different directions. The muscles are divided into right and left halves symmetrically by a connective tissue septum. On the histology of the tongue, it can be seen that the 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 the ducts of the salivary lingual glands open here. The entire surface of the tongue has a mucous membrane.
Histology of the tongue: the lower surface has an additional submucosa, and the mucosa is mobile here. The back of the tongue does not have it. And the mucosa is immobile here, tightly fused with the muscles.
Tongue histology specimen shows thatthe mucosa below is considered lining, the dorsal mucosa is specialized. On the border between the muscle thickness and the mucosa itself, there is a network of interweaving of collagen and elastic fibers - a connective tissue plate. She's pretty powerful. Its layer is called the mesh. This is nothing but the aponeurosis of the tongue.
In the region 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 holes of this mesh and attach to small tendons. This makes the aponeurosis even stronger.
Pipples
On the back and sides in the histology of the tongue, the mucosa forms special outgrowths - papillae. According to their shape, they are distinguished: filiform, mushroom-shaped, leaf-shaped (only in childhood) and grooved. They have a common structure - they are based on an outgrowth of the mucosa. Outside covered with stratified non-keratinized squamous epithelium on the basement membrane.
Filiform papillae predominate among the papillae. 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 multi-layered, flat, keratinizing. Takes part in the formation of plaque in the language. The filiform papillae roughen the tongue. Their purpose is to perform mechanical work, like scrapers. They help move the food bolus to the throat. All other papillae are taste buds.
There are no papillae at the root of the tongue. The epithelium here is uneven - with pits and elevations. Elevations areaccumulations in the mucosa of lymphatic nodules up to 0.5 cm in diameter. Their combination is called the lingual tonsil. Recesses, or crypts, are places where the salivary glands (mucous) exit through 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. The primary is covered with epithelium, like a crown.
Tongue histology specimen:
- Secondary papillae extend from the top of the primary, there are usually 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 a pink color. 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 buds (gemmaegustatoriae), are the terminal receptors of the organ of taste.
They are groups of spindle-shaped curved cells in the amount of 40-60, among which there are receptor cells. They are distinguished by the presence of microvilli at the apical end. The taste bud is oval in shape. And its apical surfaces are formed in the form of dimples, where the taste pore is located.
Particles of food with saliva get here, 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 and interact with ion flows. The tip of the tongue reacts to sweet, lateral surfaces- for s alty and sour, the root - for bitterness.
This interaction changes the potential of cell membranes, and the signal is transmitted to the nerve endings.
Mushroom papilla
Fungiform papillae are few and 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 long 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 contains 3-4 taste buds.
Grooved papillae
Grooved, or groove-like, 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 of them, stretching along the border line. Their length is 3-6 mm. Above the surface of the tongue rise clearly. In the PCT base of the papilla are the ends of the ducts of the salivary protein glands, they just open into this groove. Their secret cleanses by washing the trough of the papilla from microbes accumulating in it, food particles and desquamated epithelium.
Foliate papillae
Well developed only in children. They are located on the lateral tongue surfaces. Each group consists of 4-8 papillae, between which there are dividing narrow spaces. They are also flushed by the lingual salivary glands. The length of one papilla is about 2-5 mm.
Language development
The tongue is, in fact, an unpaired outgrowth of the floor of the mouth. Begins at 4 weeks of fetal lifethe mesenchyme at the bottom of the primary oral cavity begins to grow (proliferation). The ventral sections of the first three gill arches are involved in this.
Histology of tongue development in more detail: in the area between the first and second gill arches, an unpaired lingual tubercle is formed along the midline. A triangular dorsal part of the tongue begins to form from it.
Lateral and anterior to this first lingual tubercle, two lateral tubercles appear from the material of the first arch. They grow very quickly, approaching each other, and soon merge.
A longitudinal groove remains in the middle of their confluence. 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 that divides the tongue into 2 halves. The tip of the tongue and its body originate 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 gill arches occurs, the so-called staple.
After the development of the tongue is completed, it develops and has a border between the body and the root - a V-shaped line, the apex directed dorsally, along which the grooved papillae are located. As it grows and develops, the tongue begins to separate from the bottom of the oral cavity, and the deep grooves that form help it in this. They deepen and penetrate under its perimeter. Gradually, the formed body of the tongue develops mobility.
Histology of the muscles of the tongue proves that they develop from processesoccipital myotomes. Their cells migrate to the region of the tongue anteriorly. Its complex origin is also reflected in its innervation.
Innervation
There are a lot of free nerve endings in the language. Due to which there is such a sharp pain if you accidentally bite it. The anterior part of the tongue, 2/3, is innervated by the trigeminal nerve. Posterior third - glossopharyngeal.
In the mucosa itself is its own nerve plexus, which has nerve fibers in the bulbs of the tongue, glands, epithelium and blood vessels. At the birth of a child, 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 located next to the grooved and foliate papillae. Their end sections are in the form of branched tubules.
The mucous glands are localized on the sides and at the root. Their ends produce mucus. Mixed glands are located in the thickness of the tongue in the anterior section. They have the most ducts.
Language functions:
- mechanical processing of food, mixing and its promotion towards the pharynx;
- takes part in the production of saliva;
- helps swallow;
- participates in taste perception.
In a baby, the role of the tongue is very important when sucking milk in the first year of life. Another important aspect is the languageis the organ of articulate speech.
