The pharynx is a funnel-like muscular canal that has a length of up to 14 cm. The anatomy of this organ allows the food bolus to freely enter the esophagus, and then into the stomach. In addition, due to the anatomical and physiological features, air from the nose enters the lungs through the pharynx and vice versa. That is, the digestive and respiratory systems of a person cross in the pharynx.
Anatomical and physiological features
The upper part of the pharynx is attached to the base of the skull, the occipital bone and the temporal pyramidal bones. At the level of the 6-7th vertebrae, the pharynx passes into the esophagus.
Inside it is a cavity (cavitas pharyngis). That is, the pharynx is a cavity.
The organ is located behind the oral and nasal cavities, anterior to the occipital bone (its basilar part) and upper cervical vertebrae. In accordance with the relationship of the pharynx to other organs (that is, with the structure and functions of the pharynx), it is conditionally divided into several parts: pars laryngea, pars laryngea, pars nasalis. One of the walls (upper), which is adjacent to the base of the skull, is called the vault.
Bow
Parsnasalis is functionally the respiratory section of the human pharynx. The walls of this department are motionless and therefore do not collapse (the main difference from other departments of the organ).
The choanae are located in the anterior wall of the pharynx, and the pharyngeal funnel-shaped openings of the auditory tube, which is a component of the middle ear, are located on the lateral surfaces. Behind and above, this hole is limited by a tube roller, which is formed by a protrusion of the cartilage of the auditory tube.
The border between the posterior and upper pharyngeal wall is occupied by an accumulation of lymphoid tissue (on the midline) called adenoids, which are not very pronounced in an adult.
Between the soft palate and the orifice (pharyngeal) of the tube there is another accumulation of lymphatic tissue. That is, at the entrance to the pharynx there is an almost dense ring of lymphatic tissue: lingual tonsil, palatine tonsils (two), pharyngeal and tubal (two) tonsils.
Mouth
Pars oralis is the middle section in the pharynx, in front of which communicates through the pharynx with the oral cavity, and its back part is located at the level of the third cervical vertebra. The functions of the oral part are mixed, due to the fact that the digestive and respiratory systems intersect here.
Such a crossover is a feature of the human respiratory system and was formed during the development of the respiratory organs from the primary intestine (its wall). The oral and nasal cavities were formed from the nasorotic primary bay, the latter being located at the top and slightly dorsally relative tooral cavity. The trachea, larynx, and lungs developed from the wall of the (ventral) foregut. That is why the head section of the gastrointestinal tract is located between the nasal cavity (upper and dorsal) and the respiratory tract (ventrally), which explains the intersection of the respiratory and digestive systems in the pharynx.
Garyngeal part
Pars laryngea is the lower part of the organ, located behind the larynx and runs from the beginning of the larynx to the beginning of the esophagus. The laryngeal entrance is located on its front wall.
Structure and functions of the pharynx
The basis of the pharyngeal wall is a fibrous membrane, which is attached to the bone base of the skull from above, lined inside with mucous membranes, and outside - with a muscular membrane. The latter is covered with thin fibrous tissue, which unites the pharyngeal wall with neighboring organs, and from above, goes to m. buccinator and turns into her fascia.
The mucosa in the nasal segment of the pharynx is covered with ciliated epithelium, which corresponds to its respiratory function, and in the underlying sections - with flat stratified epithelium, due to which the surface becomes smooth and the food bolus easily slips when swallowing. In this process, the glands and muscles of the pharynx also play a role, which are located circularly (constrictors) and longitudinally (dilators).
The circular layer is more developed and consists of three constrictors: superior constrictor, middle constrictor and inferior pharyngeal constrictor. Starting at different levels:from the bones of the base of the skull, the lower jaw, the root of the tongue, the cartilage of the larynx and the hyoid bone, the muscle fibers are sent back and, united, form the pharyngeal suture along the midline.
The fibers (lower) of the lower constrictor are connected to the muscular fibers of the esophagus.
Longitudinal muscle fibers make up the following muscles: stylopharyngeal (M. stylopharyngeus) originates from the styloid process (part of the temporal bone), passes down and, dividing into two bundles, enters the pharyngeal wall, and is also attached to the thyroid cartilage (its top edge) palatopharyngeal muscle (M. palatopharyngeus).
The act of swallowing
Due to the presence in the pharynx of the intersection of the digestive and respiratory tract, the body is equipped with special devices that separate the respiratory tract from the digestive tract during swallowing. Thanks to the contractions of the muscles of the tongue, the lump of food is pressed against the palate (hard) with the back of the tongue and then pushed into the pharynx. At this time, the soft palate is pulled up (due to muscle contractions tensor veli paratini and levator veli palatini). So the nasal (respiratory) part of the pharynx is completely separated from the oral part.
At the same time, the muscles above the hyoid bone pull the larynx up. At the same time, the root of the tongue descends and presses on the epiglottis, due to which the latter descends, closing the passage to the larynx. After that, successive contractions of constrictors occur, due to which the lump of food penetrates to the esophagus. At the same time, the longitudinal muscles of the pharynx work as lifters, that is, they raise the pharynxtowards the movement of the food bolus.
Blood supply and innervation of the pharynx
The pharynx is supplied with blood mainly from the ascending pharyngeal artery (1), superior thyroid (3) and branches of the facial (2), maxillary and carotid external arteries. The venous outflow occurs in the plexus, which is located on top of the pharyngeal muscular membrane, and further along the pharyngeal veins (4) into the jugular internal vein (5).
Lymph flows into the lymph nodes of the neck (deep and behind the pharynx).
The pharynx is innervated by the pharyngeal plexus (plexus pharyngeus), which is formed by the branches of the vagus nerve (6), the sympathetic symbol (7) and the glossopharyngeal nerve. Sensitive innervation in this case passes through the glossopharyngeal and vagus nerves, with the only exception being the stylo-pharyngeal muscle, the innervation of which is carried out only by the glossopharyngeal nerve.
Sizes
As mentioned above, the pharynx is a muscular tube. Its largest transverse dimension is at the levels of the nasal and oral cavities. The size of the pharynx (its length) averages 12-14 cm. The transverse size of the organ is 4.5 cm, that is, more than the anterior-posterior size.
Diseases
All diseases of the pharynx can be divided into several groups:
- Inflammatory acute pathologies.
- Injuries and foreign bodies.
- Chronic processes.
- Tonsil lesions.
- Angina.
Inflammatory acute processes
Amongacute inflammatory diseases, the following can be distinguished:
- Acute pharyngitis - damage to the lymphoid tissue of the pharynx due to the multiplication of viruses, fungi or bacteria in it.
- Candidiasis of the pharynx - damage to the mucous membrane of the organ by fungi of the genus Candida.
- Acute tonsillitis (tonsillitis) is a primary lesion of the tonsils, which is of an infectious nature. Angina can be: catarrhal, lacunar, follicular, ulcerative-film.
- Abscess in the root of the tongue - purulent tissue damage in the area of the hyoid muscle. The cause of this pathology is infection of wounds or as a complication of inflammation of the lingual tonsil.
Throat injuries
The most common injuries are:
1. Various burns caused by electrical, radiation, thermal or chemical effects. Thermal burns develop as a result of getting too hot food, and chemical burns - when exposed to chemical agents (usually acids or alkalis). There are several degrees of tissue damage during burns:
- First degree characterized by erythema.
- Second degree - bubble formation.
- Third degree - necrotic tissue changes.
2. Foreign bodies in the throat. It can be bones, pins, food particles and so on. The clinic of such injuries depends on the depth of penetration, localization, size of the foreign body. More often there are stabbing pains, and then pain when swallowing, coughing, or a feeling of suffocation.
Chronic processes
Among chronic lesions of the pharynx are often diagnosed:
- Chronic pharyngitis is a disease characterized by lesions of the mucous membrane of the pharyngeal posterior wall and lymphoid tissue as a result of acute or chronic damage to the tonsils, paranasal sinuses, and so on.
- Pharyngomycosis is damage to the tissues of the pharynx caused by yeast-like fungi and developing against the background of immunodeficiencies.
- Chronic tonsillitis is an autoimmune pathology of the palatine tonsils. In addition, the disease is allergic-infectious and is accompanied by a persistent inflammatory process in the tissues of the palatine tonsils.
