Pharynx
The pharynx is a cylindrical, slightly sagittally compressed funnel-shaped muscle tube 12 to 14 cm long, located in front of the cervical vertebrae. The vault of the pharynx (upper wall) connects to the base of the skull, the posterior part is attached to the occipital bone, the lateral parts to the temporal bones, and the lower part passes into the esophagus at the level of the sixth vertebra of the neck.
The pharynx is the intersection of the respiratory and digestive tracts. The food mass from the oral cavity during the swallowing process enters the pharynx, and then into the esophagus. Air from the nasal cavity through the choanae or from the oral cavity through the pharynx also enters the pharynx, and then into the larynx.
Pharyngeal structure
In the anatomical structure of the pharynx, there are three main parts - the nasopharynx (upper part), oropharynx (middle part) and hypopharynx (lower part). The oropharynx and nasopharynx are connected to the oral cavity, and the hypopharynx is connected to the larynx. The pharynx is connected to the oral cavity through the pharynx, and it communicates with the nasal cavity through the choanae.
The oropharynx is an extension of the nasopharynx. The soft palate, palatine arch, and dorsum of the tongue separate the oropharynx from the oral cavity. The soft palate descends directly into the pharyngeal cavity. During swallowing and pronunciation of sounds, the palate rises upward, thereby ensuring articulate speech and preventing food from entering the nasopharynx.
The laryngopharynx begins in the region of the fourth to fifth vertebra and, smoothly going down, passes into the esophagus. The anterior surface of the laryngopharynx is represented by the area where the lingual tonsil is located. Once in the oral cavity, the food is crushed, then the food lump enters the esophagus through the larynx.
On the lateral walls of the pharynx there are funnel-shaped openings of the auditory (Eustachian) tubes. This structure of the pharynx helps to balance the atmospheric pressure in the tympanic cavity of the ear. In the area of these holes, the tonsils are placed in the form of paired accumulations of lymphoid tissue. Similar accumulations are found in other parts of the pharynx. Lingual, pharyngeal (adenoid), two tubal, two palatine tonsils form a lymphoid ring (Pirogov-Valdeyer ring). The lymphoid ring prevents foreign substances or microbes from entering the human body.
The pharyngeal wall consists of the muscular layer, the adventitia and the mucous membrane. The muscular layer of the pharynx is represented by a group of muscles: the stylopharyngeal muscle that lifts the larynx and pharynx and arbitrary paired striated muscles - the upper, middle and lower pharyngeal compressors, narrowing its lumen. When swallowing, by the efforts of the longitudinal muscles, the pharynx rises, and the striated muscles, contracting sequentially, push the food bolus.
The submucosa with fibrous tissue is located between the mucous membrane and the muscular membrane.
The mucous membrane in different locations is different in its structure. In the laryngopharynx and oropharynx, the mucosa is covered with stratified squamous epithelium, and in the nasopharynx - ciliated epithelium.
Pharyngeal functions
The pharynx takes part in several vital functions of the body at once: food intake, breathing, voice formation, and defense mechanisms.
All parts of the pharynx are involved in the respiratory function, since air passes through it, entering the human body from the nasal cavity.
The voice-forming function of the pharynx is the formation and reproduction of sounds generated in the larynx. This function depends on the functional and anatomical state of the neuromuscular apparatus of the pharynx. During the pronunciation of sounds, the soft palate and tongue, changing their position, close or open the nasopharynx, providing the formation of timbre and pitch of the voice.
Pathological changes in the voice can occur due to impaired nasal breathing, congenital defects of the hard palate, paresis or paralysis of the soft palate. Violation of nasal breathing most often occurs due to an increase in the nasopharyngeal tonsil as a result of the pathological proliferation of its lymphoid tissue. The proliferation of the adenoids increases the pressure inside the ear, while the sensitivity of the tympanic membrane is significantly reduced. The circulation of mucus and air in the nasal cavity is inhibited, which contributes to the multiplication of pathogens.
The alimentary function of the pharynx consists in the formation of acts of sucking and swallowing. The protective function is performed by the lymphoid ring of the pharynx, which, together with the spleen, thymus and lymph nodes, forms a single immune system of the body. In addition, many cilia are located on the surface of the pharyngeal mucosa. When the mucous membrane is irritated, the muscles of the pharynx contract, its lumen narrows, mucus is secreted, and a pharyngeal gag reflex appears. With a cough, all harmful substances adhering to the cilia are removed.
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