Jacobson Anastomosis: Structure, Function & Diseases

The Jacobson anastomosis is a bundle of nerve fibers in the head and skull region. Its fiber course is responsible for parasympathetic excitation (innervation) of the parotid gland. These nerve connections were discovered by the Jewish-Danish physician and researcher Ludwig Levin Jacobson (1783-1843). They originate in the nucleus salivatorius inferior, a cranial nerve nucleus in the medulla oblongata. Together with the IX cranial nerve (glossopharyngeal nerve), their pathway leads out of the cranial cavity through an opening in the base of the skull called the jugular foramen.

What is Jacobson’s anastomosis?

Among some other connections (anastomoses) with neighboring nerves, the fibers enter the so-called tympanic cavity (cavitas tympani). Finally, the crucial distribution station of the branches in front of the parotid gland is the facial nerve. Thus, the Jacobson anastomosis finally reaches its destination, the parotid gland, as a parasympathetic cord of the glossopharyngeal nerve (“tongue pharyngeal nerve”). The unmanageable network of nerves around the IXth cranial nerve also guarantees the supply of the middle ear, the so-called cheek glands, the pharyngeal mucosa, the tonsils as well as the rear areas of the tongue. In this highly sensitive area, various muscle spasms can occur due to defects of the glossopharyngeal nerve. Possible triggers for this include tetanus, rabies or strong irritant effects caused by foreign bodies. Damage to the glossopharyngeus can also lead to paralysis of the pharyngeal muscles and, as a consequence, to massive swallowing disorders. In such cases, the so-called nerve-muscle coupling is thrown out of its usual balance. Glossopharyngeal neuralgia can also occur in connection with Jacobson’s anastomosis. In this case, sudden severe pain occurs in the wider mouth area, which may extend to the ear region. They are clearly noticeable with the simplest movements of chewing, swallowing, and speaking.

Anatomy and structure

The parotid gland (parotid gland or glandula parotis), supplied with nerve stimuli by Jacobson’s anastomosis, is considered the largest salivary gland in the entire maxillofacial area. It is located on both sides of the face, in front of and below the ear. In its extension, the parotid gland reaches from the so-called zygomatic arch to the angle of the jaw. The shape is triangular and flat. The parotid gland weighs 20 to 30 grams. It is covered with a fascia (capsule of connective tissue). Inside it is divided into small lobules. There are the glandular cells of the parotid gland, which secrete the so-called primary saliva. This has the peculiarity of changing its composition the further it advances in the draining system. The so-called excretory duct of the parotid gland runs largely in a similar way to the masticatory muscles. It passes through the cheek muscle and the cheek mucosa. The end point of the parotid excretory duct is in the oral cavity. As a rule, it is easily recognizable in the oral cavity opposite the upper molars as a small dark-colored dot. In addition to the Jacobson’s anastomosis leading to the parotid gland, the parotid plexus is also found in the parotid gland. This is composed of fibers of the VII cranial nerve (facial nerve). The fibers leading away from it are essentially responsible for the activation of the mimic facial musculature. The parotid gland is also reached by branches and offshoots of the trigenic nerve. In the area of the parotid gland, the external carotid artery also divides into its two terminal branches. The outflow of blood is initially via branches of the parotid vein. Lymph from the parotid gland passes externally through the so-called parotid lymph nodes.

Function and tasks

The saliva produced by the parotid gland is in a so-called pure liquid state, that is, watery and entirely devoid of mucous (slimy) components. It is thin, slightly in the alkaline range, and has relatively large proportions of proteins and enzymes. Of these, the enzyme amylase is particularly important for the decomposition of carbohydrates. The saliva of the parotid gland is also characterized by its content of immunoglobulins, which serve the biological defense in the mouth area. More or less common diseases of the parotid gland are tumors and mumps (goat’s peter). Mumps occurs mainly in childhood and is characterized by severe swelling of the parotid gland as a result of a viral infection.Such swellings, since they can have the most diverse malignant causes, should always be carefully examined by a specialist. The main danger is that the inflammatory swellings can quickly spread to sensitive areas of the brain.

Diseases

Various malfunctions of the Jacobson anastomosis can lead to a whole range of impairments of the parotid gland. Inflammation in particular spreads quickly because the parotid gland with its glandular duct has open access to the oral flora. The salivary flow of the gland is occasionally massively impeded by the formation of stones. Dangerous bacteria find easy access through these salivary stones, which in turn can trigger new inflammations. It is not uncommon for chronic infections to occur, which must be treated with antibiotics. Salivary stones are usually preceded by a change in the composition of saliva. They consist mainly of calcium phosphate and can usually be removed by simple surgical methods. Using ultrasound, it is also possible to break up the salivary stones so that they can be removed naturally through the canal system. Benign tumors affecting salivary glands in the human body affect the parotid gland in about 80 percent of cases. Since they can degenerate, removal is still recommended under certain circumstances. In contrast, removal of malignant tumors of the parotid gland is often the only possible therapy. However, the risk of this surgery is high because a large number of facial nerves pass through the parotid gland.