The submandibular ganglion is a collection of nerve cell bodies in the mandibular region. The ganglion interconnects parasympathetic nerve fibers in the course to the mandibular salivary glands and serves as a transit station for sympathetic fibers from the glands. Damage to the mandibular ganglion can interfere with salivary secretion from the sublingual and submandibular glands.
What is the submandibular ganglion?
Ganglia are nodular thickenings of collections of nerve cell bodies in the peripheral nervous system. In German literature, they are also referred to as ganglions because of their nodular shape. In the human nervous system there are different ganglia with parasympathetic qualities. The parasympathetic nervous system is a part of the autonomic nervous system, which controls all autonomic body processes in interaction with the antagonistic sympathetic nervous system. The submandibular ganglion corresponds to a parasympathetic nerve node of the head region. The ganglion has its exact localization in the trigonum submandibulare, a triangle-shaped area of the anterior neck region. The nerve node is a distribution site for sympathetic nerve fibers, which pass through the structure unconnected. Only the parasympathetic fibers of the ganglion are interconnected within the nerve node. For this reason, the term parasympathetic ganglion is used. In German literature, the submandibular ganglion is referred to as the mandibular ganglion.
Anatomy and structure
The submandibular ganglion is located immediately above the salivary gland of the same name, the submandibular gland. Here, the ganglion is adjacent to the hyoglossus muscle and the posterior mylohyoid muscle. Two connecting fiber bundles exist to the lingual nerve. The parasympathetic head ganglion carries parasympathetic and sympathetic fiber qualities, but is not traversed by somatic fibers. The parasympathetic fibers of the structure originate from neurons in the superior salivatory nucleus, which reach the ganglion via the facial nerve and the tympanic chorda and lingual nerve. Postganglionically, the submandibular ganglion receives sympathetic nerve fibers from the superior cervical ganglion. These fibers enter the ganglion via the external carotid plexus as well as the facial artery. Overall, the mandibular nerve node turns out to be rather small and bears the shape of a spindle.
Function and Tasks
For all sympathetic fibers, the submandibular ganglion does not assume an active role but corresponds to a passive transit station. Without switching, these fibers pass through the ganglion and move on to the salivary glands. Only parasympathetic nerve fibers are switched in the submandibular ganglion. Thus, the nerve node represents a switching station for the parasympathetic nervous system. Nerve fibers with parasympathetic quality are switched within the structure to the second, postganglionic neuron of the lingual nerve fibers (lingual nerve). After this switching, the postganglionic fibers form the so-called rami glandulares and draw to the two salivary glands in the mandibular region (sublingual and submandibular glandula). These glands are innervated visceromotorly by the nerves. The visceromotor innervation corresponds to an innervation that cannot be influenced voluntarily. That is, the associated musculature belongs to the involuntary body musculature. Movements of involuntary muscles escape conscious control and are controlled purely by the autonomic nervous system. Such musculature governs the movements of the three major salivary glands. The submandibular ganglion is indirectly involved in the sympathetic as well as parasympathetic innervation of these salivary glands. Via the parasympathetic nerves, the autonomic nervous system stimulates the salivary glands to activity. The sympathetic nerves in turn inhibit the activity of the salivary glands. This is the case, for example, in extreme situations. In such stressful situations, the body prepares itself for peak performance by increasing sympathetic nerve activity in order to survive stress. Body functions that can be dispensed with for the time being, such as the secretion of saliva, are reduced so that the organism can concentrate its energies on the body functions that sustain life. In relaxation situations, the parasympathetic influence on the large salivary glands predominates. Thus, salivary secretion increases substantially compared to the stress situation.The stress-related effects of the sympathetic nervous system on the salivary glands are a familiar situation for joggers, for example. During running, the mouth often becomes extremely dry and swallowing becomes increasingly difficult.
Diseases
The structures of the submandibular ganglion can be damaged by various processes. In addition to trauma, tumors or inflammation, for example, can affect the nerve structures of the ganglion. Depending on the degree of damage and the quality of the damaged structures, different disturbances of salivary secretion occur due to nerve lesions in the area of the ganglion. If the parasympathetic influence fails, for example, the secretory activity of the glands ceases. If, on the other hand, the sympathetic influence decreases, the parasympathetic nervous system stimulates the glands to secrete almost uninhibitedly. Increased salivation is known as hypersalivation. Decreased salivation is known as hyposalivation. Damage to the submandibular ganglion affects only the salivary secretion of the mandibular salivary glands, the sublingual and submandibular glands. All other salivary glands function undisturbed despite impairment of the submandibular ganglion. Therefore, even after damage to the submandibular nerve node, for example, there may not be a complete stop to salivary secretion, but at most a discrete increase or decrease in salivary output. Signs of excessive influence of the sympathetic nervous system may include dry mouth as well as dysphagia or bad teeth. Not all secretory disorders of the mandibular salivary glands must have something to do with damage to the submandibular ganglion. Many diseases are associated with disorders of salivary secretion, such as glandular diseases like salivary gland tumors. Metabolic diseases and hormonal dysfunctions also show effects on saliva production and secretion. In addition, the nerve structures involved in the ganglion can also be damaged at sites outside the nerve node and thus also cause salivary secretion disorders. For this reason, impaired salivary secretion from the mandibular salivary glands is by no means equivalent to definite damage to the mandibular nerve node.
