THE LINGUAL, SINUS AND PHARYNGEAL MUCOSA
I- The language:
The tongue is a mobile musculoskeletal organ, occupying the greater part of the oral cavity, it participates in: chewing, the formation of the food bolus, swallowing, tasting and phonation.
II- Anatomy:
It consists of two (2) parts:
-A fixed part inserted into the pharynx.
-A mobile part presenting:
- Two lateral edges: have papillae called foliate papillae (corolliform).
- A tip.
- The base: is entirely pharyngeal.
- The upper surface (back of the tongue) : pink in color, constantly moist and with lingual (taste) papillae on its surface
- The lower surface: has a thinner mucosa crossed by a median groove which extends into the frenulum of the tongue.
-The Ranine veins.
-Wharton’s duct is the excretory duct of the submandibular gland.
III- Histology of the lingual mucosa:
The lingual mucosa consists of non-keratinized squamous epithelium associated with an underlying lamina propria.
Beneath the mucosa, skeletal striated muscle bundles are arranged perpendicular to each other in the three orthogonal directions. They are intertwined with numerous serous and mucous salivary glandular lobules.
1-The upper face:
It presents to describe lingual papillae of which we distinguish 3 types according to their shapes, their locations and their functions:
A- Filiform papillae (filiform papillae) :
They are the most numerous, long, thin, straight and covering the entire lingual surface, they give the tongue its rough appearance. They are devoid of taste buds and are formed by the simple elevation of the lingual epithelium by a conjunctivo-vascular axis. The tip undergoes pseudo-keratinization.
The conjunctivovascular axis contains numerous nerve endings.
They have an essentially tactile role.
B-Fungiform papillae (papillae fungiformes):
Mushroom-shaped as their name suggests, they are larger and less numerous. Scattered between the filiform papillae and close together at the tip. They appear to the naked eye as small red granules, they are cylindrical extensions of the mucosa, with a swollen and smooth end, covered by a buccal-type epithelium. The conjunctivo-vascular axis is more developed and more massive and contains nerve fibers related to the taste buds.
C-Circumvallate (or caliciform) papillae:
There are 12 of them, they are large (1 to 3 mm in diameter) located at the back of the tongue and forming the lingual V.
They are formed by a central, cylindrical projection of non-keratinized epithelium. Its upper surface is flat, surrounded by a smooth-walled groove or ditch (Vallum) at the bottom of which open the excretory ducts of accessory serous glands of Von Ebner and mucous glands.
D-Foliate or foliaceous papillae (papillae foliatae):
Are located at the posterior end of the lateral edges of the tongue; there are 300 on each side of the tongue, they are irregular formations represented by leaflets separated by vertical grooves, they are rich in taste buds (about 50 per papilla) and serous accessory glands open into the depth of the grooves.
Taste buds:
They are chemoreceptors that allow them to receive taste sensations, they have an ovoid or conical shape and are located in the epithelium, their elective seat is in the caliciform and fungiform papillae, their number reaches up to 10,000 in humans.
These organs are related to the nerve endings of different sensory nerves in the oral cavity.
On the chorion side, they are connected with the nerve endings by a simple internal pore kept permanently open.
Each taste bud contains:
a- Clear supporting cells: fusiform in shape, curved, located on the periphery, often in mitosis, they secrete RANVIER’s mucoid substance.
b- Flattened basal epithelial cells.
c- Dark sensory (gustatory) cells in the center (4 to 6 in humans) containing the taste rods.
IV-STRUCTURE OF THE LANGUAGE:
1-An osteo-fibrous skeleton:
– The hyoid bone
– Two 2 fibrous membranes:
- The lingual septum: separates the tongue into two halves
- The hyoglossian membrane.
2- Powerful muscles: (17 muscles)
-Extrinsic muscles: there are 5 pairs
- Genioglossus,
- Hyoglossus,
- Palatoglossus,
- Pharyngoglossus,
- Styloglossus.
-Intrinsic muscles:
(3 pairs)
- the lower longitudinal or lower lingual muscles,
- vertical muscles,
- transverse muscles
and an odd one: Superior longitudinal or superior lingual muscle
V-VASCULARIZATION OF THE TONGUE:
Provided by
-The LINGUAL ARTERY comes from the external carotid and gives 3 branches:
- Dorsal artery of the tongue,
- Sublingual artery,
- Deep lingual artery
VI-INNERVATION OF THE TONGUE:
The tongue has a triple innervation:
- Motor: the tongue has intrinsic (shape of the tongue) and extrinsic (position of the tongue) muscles.
- Sensitive: like any mucous membrane, the surface of the tongue is sensitive to mechanical stimuli, heat, cold, pain.
- Sensory: the tongue is the organ of taste.
The sinus mucosa
The respiratory mucosa and the mucosa of the conduction tract are present from the nasal cavities to the terminal intrapulmonary bronchioles.
The sinuses are air-filled cavities dug into the thickness of the facial bones. There are four pairs of paranasal sinuses which are:
-the frontal sinus
-the ethmoid sinus
-the sphenoid sinus
-the maxillary sinus
I-THE MAXILLARY SINUS:
1-DEFINITION:
The maxillary sinuses are two cavities occupying the middle third of the face on either side of the nasal fossae, below the orbits and laterally above the premolar-molar sectors.
2-ANATOMY:
It is the largest of the paranasal sinuses.
-it is radio clear on standard X-ray.
-It has a pyramidal shape with an internal base and an external summit. It drains through the middle meatus into the nasal cavity.
– 5 walls are described at its level: the upper wall, the posterior wall, the lower wall, the anterior wall and the medial wall
A-The upper wall
-It constitutes the largest part of the floor of the orbit, it is thin.
-It is crossed by the groove and the infraorbital canal
B- The posterior wall:
It is more than 2 mm thick and has two parts:
– a concave anterior part (the retro-maxillo-zygomatic groove)
– a convex part, the maxillary tuberosity.
C-The lower wall:
It constitutes the sinus floor of a gutter shape with upper concavities.
It molds to the dental apices and takes on a thickness of 3 to 4 mm, but sometimes it is reduced to a simple mucosa where one can see the dental apices of the sinus teeth.
D-The anterior or anterolateral wall:
-It corresponds to the jugal face.
-It is thick in its lower part and thins towards the lower orbital rim.
E- The medial part (called nasal):
It occupies the lower half of the external wall of the nasal cavities.
It contains the ostial canal which connects the maxillary sinus with the nasal cavity.
This gas exchange and secretion drainage link measures 6 to 8 mm long and 3 to 5 mm in diameter.
Filling this ostium or the risk of wanting to block it constitutes a contraindication to sinus floor lifting.
3-HISTOLOGY OF THE SINUS MUCOSA:
All sinus walls are lined by a thin, flexible mucosa, measuring approximately 0.2 to 0.8 mm.
It is composed of respiratory epithelium and underlying connective tissue.
Histology of the sinus mucosa
3-1-The respiratory epithelium:
It is a pseudo-stratified epithelium, that is to say a simple epithelium comprising a single cell layer, but which resembles, on histological sections, a stratified epithelium: all the cells are in contact with the basal lamina, but not all reach the apical pole which comprises four types of cells:
- Cyliated cylindrical cells, majority.
- Goblet mucous cells.
- Replacement basal cells.
- Endocrine cells, minority.
a- Basal cells:
Represent 1/3 of epithelial cells. They have a triangular shape on sections.
Their nucleus is located in the lower third of the epithelium.
They constitute the epithelial stem cells capable of generating all other cell types.
b- The majority of hair cells:
The most abundant. They are dedicated to the functioning of the mucociliary escalator.
Prismatic in shape with the nucleus located in the upper third of the epithelium.
Rich in apical mitochondria which are necessary for cilia to function
vibratile and membrane ion pumps.
At the apical pole level they present two remarkable formations:
- Vibrating eyelashes (200 to 300 eyelashes/cell)
- Small microvilli between the cilia (increased exchanges).
Hair cells
c- Mucus goblet cells:
Have a dilated, clear apical pole, filled with mucin grains.
They have a calyx or jar shape, with an apical pole dilated relative to the basal pole.
Their nucleus has a triangular appearance with an apical base and a basal apex and is located in the lower part of the cell (lower third of the epithelium).
Mucus goblet cell
d-Endocrine cells:
They are in the minority (3 to 5%), do not reach the apical pole of the epithelium
Their nucleus is in an apical position (unlike the others); the secretory granules are concentrated in the basal pole and the secretory products will be diffused into the chorion
3-2-The basal lamina:
It is rich in type IV collagen consisting of a microfibrillar lamina densa and a lamina lucida rich in laminin.
3-3-The chorion:
It presents a rich lymphoid infiltrate, in the form of isolated lymphocytes, dispersed in the chorion, or grouped in primary or secondary follicles and monocytes/macrophages, IgA-secreting plasma cells, and pro-inflammatory cells, such as mast cells or polymorphonuclear cells.
– Very rich in elastic fibers
– Tubuloacinar exocrine glands:
- Serous: Serous glands secrete very fluid protein solutions.
- Mucous membrane: Mucous glands secrete mucins.
- Seromucosal or mixed.
– Hyper-vascularization :
This hypervascularization is characteristic of the mucosa of the nasal cavities and sinuses.
4- ROLES OF THE SINUS:
- Secretion of mucus having an important role in antibacterial defense and against dust and foreign debris.
- Ciliary activity, creating an evacuation current towards the high ostium with a reduced diameter and a counter current which opposes the penetration of foreign particles.
- Air heating by the venous plexus under the epithelial tissue of the sinus mucosa.
- Immune role through the presence of lymphocytes and macrophages. It is in the maxillary sinuses that the highest concentration of bacteria and allergenic particles are found.
- Vocal resonators.
- Skull relief.
The pharynx
The pharynx is the aerodigestive crossroads. It is made up of a framework covered with mucous membrane.
1-The frame:
The framework of the pharynx is musculo-membranous; The pharynx is a deformable organ composed of membranes and striated muscle fibers. These muscle fibers constitute the constrictor muscles of the pharynx (about twenty muscles)
- In summary, we can remember that their contraction is synchronized with the inspiratory phase which stiffens the wall of the pharynx
2-The mucous membranes of the pharynx: (especially respiratory type)
There are three parts: the nasopharynx, the oropharynx and the laryngo-pharynx.
A-The Nasopharynx:
Mucosa of the respiratory region (contact with only one fluid, air):
Respiratory epithelium consisting of three types of cells:
- Hair cells,
- Goblet cells
- Basal cells.
B-The oropharynx:
Located in the aerodigestive junction. Formed of an epidermoid epithelium (non -keratinized malpighian epithelium more resistant than the respiratory epithelium, and which is found in the rest of the oral mucosa and the tongue).
C-The laryngo-pharynx:
It is an integral part of the digestive tract, its mucosa will be an extension of the esophageal mucosa.
3-Particularity of the pharyngeal mucosa
Some elements are overdeveloped at the level of the pharynx, forming quasi-secondary lymphoid organs, better known as tonsils:
- Palatine tonsils
- Tubal tonsils
- Adenoids or adenoids
- Lingual tonsils
Making the Waldeyer ring around the mouth.
THE LINGUAL, SINUS AND PHARYNGEAL MUCOSA
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