The posterior vagal trunk is a nerve branch of the vagus nerve with involvement particularly in the parasympathetic innervation of the kidneys and stomach. The visceromotor fibers of the posterior vagal nerve partially control the involuntary organ activity of the abdominal organs. Failure of the posterior vagal trunk results in dysregulation of the kidneys and stomach.
What is the posterior vagal trunk?
The vagus nerve is considered the tenth cranial nerve and also the largest nerve of the parasympathetic nervous system. Its branches parasympathetically regulate approximately all activities of the abdominal and thoracic organs. “Nervus vagus” in literal translation means “roving nerve”. The posterior vagal trunk corresponds to a branch of the vagus nerve that originates in the esophageal plexus. This is the nerve plexus of the esophagus from which the truncus originates between the thoracic inlet and the diaphragmatic passage. The anterior vagal nerve also has its origin in this plexus, with both nerve branches exchanging fibers. The esophageal plexus, along with the vagus nerve, gives off fibers to the esophageal area, becoming the gastric plexus and connecting with the cardiac plexus. The posterior vagal trunk itself gives off different nerve branches with a parasympathetic vegetative quality. In addition to rami gastrici, it sends rami coeliaci and rami renales. In keeping with the name affix “posterior,” the vagus nerve portion innervates the posterior surface of the stomach, while the truncus vagalis anterior innervates the anterior surface of the stomach in a parasympathetic and visceromotor fashion. The vagus nerve itself contains general somatosensory as well as general visceromotor and special visceromotor fibers. In addition, it carries general-viscerosensitive and special-viscerosensitive fiber portions.
Anatomy and structure
The posterior vagal truncus carries parasympathetic fibers of the vagus nerve, which originate from the medulla oblongata. The associated nucleus consists of general visceromotor fibers and is regulated in the nucleus by afferent sensory fibers from the nucleus tractus solitarii and hypothalamus. Accordingly, the trunci vagalis consist of general viscerosensitive and parasympathetic nerve fibers. Together, they supply the abdominal organs of the stomach, kidney, pancreas, liver, gallbladder, and intestine. The posterior vagal trunk is a right vagus nerve that runs on the right side of the esophagus along with the left vagus nerve. Due to rotation of the stomach during embryonic development, the right vagus nerve continues posteriorly. In contrast, the left vagus nerve continues forward. The fibers of the two trunci are in exchange with each other. Thus, the posterior vagal truncus also contains fibers of the anterior vagal truncus. With the esophagus, the posterior vagal truncus passes through the esophageal hiatus, an opening in the diaphragm. The nerve then splits. The smaller portion of the split fibers becomes the ramus gastricus, which pulls onto the stomach to form the oesophageal plexus. After splitting, the major portion of the fibers forms the ramus coeliacus, which contributes to the coeliac plexus.
Function and Tasks
The vagus nerve parasympathetically regulates thoracic as well as abdominal organs. This parasympathetic organ innervation corresponds to autonomic innervation. The autonomic nervous system is an autonomic nervous system that draws its autonomy from biologically determined, automatic processes of the organs. Parasympathetic vegetative regulation is not necessarily consciously perceived by humans and eludes direct volitional influence. The truncus vagalis posterior contains fibers for conducting visceroefferent signals. For example, the posterior vagal trunk with its parasympathetic rami is involved in posterior gastric surface activity and renal activity. Through viscerosensitive fibers of the trunci, the autonomic nervous system is permanently aware of organ activity and can adjust it in a regulatory manner. Like all autonomic nerve fibers, those of the posterior vagal truncus are required for survival. The vagus nerve sends fibers to both smooth and striated muscles, making it one of the most relevant nerves for regulating abdominal organ activity. In the medulla oblongata and spinalis, its nucleus spinalis nervi trigemini is located. This nucleus contains the general somatosensitive fibers of the vagus nerve.The medulla oblongata is also the origin of general vagus visceromotor fibers, the dorsal nucleus nervi vagi. Specialized vagus visceromotor fibers originate from the nucleus ambiguus, which is also located in the medulla oblongata. In contrast, general- and special-viscerosensitive vagus fibers arise from the nucleus tractus solitarii.
Diseases
A relatively common phenomenon in pathophysiology is compression of the vagus nerve. Compression or entrapment of the nerve can result in posterior vagal trunk dysfunction. The vagus nerve sends its nerve fibers near the atlas, which is near the first cervical vertebra. When the atlas is misaligned, compressions are common because the vagus nerve fibers can become jammed at the atlas in this case. Severe atlas misalignments put pressure on the vagus nerve, irritating the nerve. This can result in functional impairment. The most common symptoms of vagus compression are nausea, hyperacidity or dizziness. Accompanying symptoms may include facial flushing, excessive heartbeat and neck pain, and headache. In addition, common symptoms of vagus compression include difficulty swallowing, sweating, sleep disturbances, constipation or diarrhea, and thyroid and kidney problems. Failure of the posterior truncus vagalis specifically results in gastric and renal regulatory complaints. Isolated failures of the posterior vagal trunk are rare. At least the anterior vagal trunk is usually involved. The autonomic nervous system rarely develops primary disease. Any damage to the autonomic nerves is usually mechanical or traumatic and may thus be due, for example, to accidental lesions in the spinal cord. Complete failure of the autonomic nervous system results in death and is not common. Parasympathetic and sympathetic nervous systems together form the autonomic nervous system and have an antagonistic relationship with each other. They regulate each other with their fibers interacting. Therefore, a failure of one of the two fiber qualities can already lead to severe organ dysfunction, which manifests itself in hyperactivity of the respective antagonist.
