The pharynx is a funnel-like muscle channel that is up to 14 cm long. The anatomy of this organ allows the food lump to enter the esophagus unhindered, and then into the stomach. In addition, due to the anatomical and physiological characteristics, air passes from the nose into the lungs and back through the pharynx. That is, the human digestive and respiratory systems cross in the throat.
Anatomical and physiological features
The upper part of the pharynx is attached to the base of the skull, occipital bone and 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 the cervical upper vertebrae. In accordance with the attitude of the pharynx to other organs (i.e., 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 arch.
Fore part
Pars nasalis in functional terms is the respiratory section of the human pharynx. The walls of this department are motionless and therefore do not collapse (the main difference from other parts of the organ).
Hoans are located in the anterior wall of the pharynx, and pharyngeal funnel-shaped openings of the auditory tube, which is a component of the middle ear, are located on the lateral surfaces. At the rear and at the top, this hole is limited by a tube shaft, which is formed by protrusion of the cartilage of the auditory tube.
The border between the posterior and upper wall of the pharynx 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 opening (pharyngeal) of the tube is another cluster of lymph 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 tube (two) tonsils.
Mouth part
Pars oralis is the middle section in the pharynx, communicating in front of the pharynx with the oral cavity, and its posterior 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 cross here.
Such a cross is a feature of the human respiratory system and was formed during periods of development of the respiratory organs from the primary intestine (its wall). From the nasal cavity of the primary bay, the oral and nasal cavities were formed, the latter being located at the top and slightly dorsally relative to the oral cavity. Trachea, larynx and lungs developed from the wall (ventral) of the anterior intestine. That is why the head section of the gastrointestinal tract is located between the nasal cavity (above and dorsally) and the respiratory tract (ventrally), which explains the intersection of the respiratory and digestive systems in the pharynx.
Larynx
Pars laryngea is the lower part of the organ, located behind the larynx and goes from the beginning of the larynx to the beginning of the esophagus. The laryngeal entrance is located on its front wall.
The structure and functions of the pharynx
The basis of the pharyngeal wall is the fibrous membrane, which is attached from above to the bone base of the skull, inside is lined with mucous membranes, and outside - by the muscular membrane. The latter is covered with thin fibrous tissue, which combines the pharyngeal wall with neighboring organs, and from above, goes to m. buccinator and turns into her fascia.
The mucous membrane in the nasal segment of the pharynx is covered with ciliated epithelium, which corresponds to its respiratory function, and in the underlying sections, by the flat multilayer epithelium, due to which the surface acquires smoothness and the food lump 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 compressors: the upper constrictor, the middle constrictor and the lower pharyngeal constrictor. Starting at different levels: from the bones of the base of the skull, lower jaw, root of the tongue, cartilage of the larynx and hyoid bone, the muscle fibers go back and, when combined, form a suture of the pharynx along the midline.
Fibers (lower) of the lower constrictor are connected with the muscular fibers of the esophagus.
The longitudinal muscle muscles comprise the following muscles: stylo-pharyngeal (M. stylopharyngeus) originates from the styloid process (part of the temporal bone), passes down and, splitting into two bundles, enters the pharyngeal wall, and also attaches to the thyroid cartilage (its upper edge); palatopharyngeal muscle (M. palatopharyngeus).
Swallowing act
Due to the presence in the pharynx of a cross of the digestive and respiratory tracts, the body is equipped with special devices that separate the respiratory tract from the digestive tract during swallowing. Due to contractions of the muscles of the tongue, a lump of food is pressed against the palate (hard) by the back of the tongue and then pushed into the throat. At this time, the soft palate is pulled up (due to muscle contractions tensor veli paratini and levator veli palatini). So the nasal (respiratory) section of the pharynx is completely divided with the oral section.
At the same time, the muscles that are located above the hyoid bone pull the larynx up. The root of the tongue at the same time drops down and presses on the epiglottis, due to which the latter falls, closing the passage to the larynx. After there are successive contractions of constrictors, due to which a lump of food penetrates the esophagus. At the same time, the longitudinal muscles of the pharynx work as lifters, that is, they raise the pharynx in the direction of movement of the food lump.
Blood supply and pharyngeal innervation
The pharynx is supplied mainly from the pharyngeal ascending artery (1), the thyroid superior (3) and the branches of the facial (2), maxillary and carotid external arteries. Venous outflow occurs in the plexus, which is located on top of the pharyngeal muscle 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 post-pharyngeal).
The pharynx is innervated by the pharyngeal plexus (plexus pharyngeus), which is formed by the branches of the vagus nerve (6), sympathetic sivol (7) and glossopharyngeal nerve. In this case, sensitive innervation passes along the glossopharyngeal and vagus nerves, with the exception of the stylo-pharyngeal muscle, the innervation of which is carried out only by the glossopharyngeal nerve.
Dimensions
As mentioned above, the pharynx is a muscle tube. Its largest transverse size is at the levels of the nasal and oral cavities. The size of the pharynx (its length) is on average 12-14 cm. The transverse size of the organ is 4.5 cm, that is, more than the anteroposterior size.
Diseases
All diseases of the pharynx can be divided into several groups:
- Inflammatory acute pathology.
- Injuries and foreign bodies.
- Chronic processes.
- Tonsil lesions.
- Sore throats.
Inflammatory Acute Processes
Among the acute 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.
- Pharyngeal candidiasis - damage to the mucous organ by fungi of the genus Candida.
- Acute tonsillitis (tonsillitis) is the primary lesion of the tonsils, which has an infectious nature. Sore throats can be: catarrhal, lacunar, follicular, ulcer-film.
- An abscess in the area of the tongue root is purulent tissue damage in the region of the hyoid muscle. The cause of this pathology is infection of wounds or as a complication of inflammation of the lingual tonsil.
Pharyngeal damage
Among injuries, the most common are:
1. Various burns caused by electric, radiation, thermal or chemical exposure. Thermal burns develop as a result of ingestion of too hot food, and chemical burns when exposed to chemical agents (usually acids or alkalis). There are several degrees of tissue damage during burns:
- The first degree is characterized by erythema.
- The second degree is the formation of bubbles.
- The third degree is 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 penetration depth, localization, size of the foreign body. Often there are stitching pains, and then pain when swallowing, coughing or a feeling of suffocation.
Chronic processes
Among chronic lesions of the pharynx, it is often diagnosed:
- Chronic pharyngitis is a disease that is characterized by lesions of the mucosa 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 tonsils. In addition, the disease is allergic and infectious and is accompanied by a persistent inflammatory process in the tissues of the tonsils.