The sympathetic nerve trunk is one of the components of the nervous peripheral part of the sympathetic system.
Building
In accordance with the structure of the sympathetic trunk (Truncus sympathicus), it is paired and is a node that is connected to each other through sympathetic fibers. These formations are located on the sides of the spinal column along its entire length.
Any of the nodes of the sympathetic trunk is a cluster of autonomic neurons that switch preganglionic fibers (most of them) that exit the spinal cord, forming connecting white branches.
The fibers described above are in contact with the cells of the corresponding node or go as part of internodal branches to the inferior or superior node of the sympathetic trunk.
Connecting white branches are located in the upper lumbar and thoracic regions. There are no branches of this type in the sacral, lower lumbar and cervical nodes.
In addition to the white branches, there are also connecting gray branches, which consist mostly of sympathetic postganglionic fibers and connect the spinal nerves with the nodes of the trunk. Such branches go toeach of the spinal nerves, moving away from each of the nodes of the sympathetic trunk. As part of the nerves, they are directed to the innervated organs (glands, smooth and striated muscles).
As part of the sympathetic trunk (anatomy), the following departments are conditionally distinguished:
- Sacral.
- Lumbar.
- Chest.
- Neck.
Functions
In accordance with the departments of the sympathetic trunk and its constituent ganglia and nerves, several functions of this anatomical formation can be distinguished:
- Innervation of the neck and head, as well as control over the contraction of the vessels that feed them.
- Innervation of the organs of the chest cavity (branches from the nodes of the sympathetic trunk are part of the nerves in the pleura, diaphragm, pericardium and ligaments of the liver).
- Innervation of the vascular walls (as part of the nerve plexuses) of the common carotid, thyroid and subclavian arteries, as well as the aorta.
- Connect the nerve ganglia to the nerve plexuses.
- Participate in the formation of the celiac, aortic, superior mesenteric and renal plexuses.
- Innervation of the pelvic organs due to the entry of branches from the cruciate ganglia of the sympathetic trunk into the lower hypogastric plexus.
Cervical sympathetic trunk
There are three nodes in the cervical region: lower, middle and upper. We will consider each of them in more detail below.
Top knot
The formation of a spindle-shaped shape with dimensions of 205 mm. It is located on2-3 cervical vertebrae (their transverse processes) under the prevertebral fascia.
Departs from the node seven main branches that carry postganglionic fibers that innervate the organs of the neck and head:
- Connecting gray branches to 1, 2, 3 spinal cervical nerves.
- N. jugularis (jugular nerve) divides into several branches, two of which are attached to the glossopharyngeal and vagus nerves, and one to the hypoglossal nerve.
- N. caroticus internus (internal carotid nerve) enters the outer shell of the internal carotid artery and forms the plexus of the same name there, from which sympathetic fibers depart in the area where the artery enters the canal of the same name on the temporal bone, which form a stony deep nerve passing through the pterygoid canal in the sphenoid bone. After leaving the canal, the fibers bypass the pterygopalatine fossa and join the parasympathetic postganglionic nerves from the pterygopalatine ganglion, as well as the maxillary nerve, after which they are sent to the organs in the face area. In the carotid canal, branches separate from the carotid internal plexus, which penetrate and form a plexus in the tympanic cavity. Inside the skull, the carotid (internal) plexus passes into the cavernous, and its fibers spread through the vessels of the brain, forming the plexus of the ophthalmic, middle cerebral and anterior cerebral arteries. In addition, the cavernous plexus gives off branches that connect with the parasympathetic fibers of the parasympathetic ciliary ganglion and innervate the muscle that dilates the pupil.
- N. caroticus externus (drowsyexternal nerve). It forms an external plexus near the artery of the same name and its branches, which supply blood to the organs of the neck, face and dura mater.
- The pharyngeal-laryngeal branches accompany the vessels of the pharyngeal wall and form the pharyngeal plexus.
- The upper cardiac nerve passes near the cervical region of the sympathetic trunk. In the cavity of the chest, it forms the superficial cardiac plexus, which is located under the aortic arch.
- Branches that are part of the phrenic nerve. Their endings are located in the capsule and ligaments of the liver, pericardium, parietal diaphragmatic peritoneum, diaphragm and pleura.
Middle knot
Formation measuring 22 mm, located at the level of the 4th cervical vertebra, in the place where the common carotid and inferior thyroid arteries intersect. This node gives rise to four types of branches:
- Connecting gray branches that go to 5, 6 spinal nerves.
- The middle cardiac nerve, which is located behind the carotid common artery. In the chest cavity, the nerve is involved in the formation of the cardiac plexus (deep), which is located between the trachea and the aortic arch.
- The branches that are involved in the organization of the nerve plexus of the subclavian, common carotid and thyroid lower arteries.
- Internodal branch that connects to the cervical superior sympathetic node.
Lower knot
The formation is located behind the vertebral and above the subclavian arteries. In rare casesunites with the first sympathetic thoracic node and is then called the stellate (cervicothoracic) node. The bottom node gives rise to six branches:
- Connecting gray branches to 7, 8 spinal cervical nerves.
- A branch leading to the plexus vertebralis, extending into the skull and forming the plexus of the posterior cerebral artery and the basilar plexus.
- The lower cardiac nerve, which lies behind the aorta on the left, and behind the brachiocephalic artery on the right, and is involved in the formation of the deep cardiac plexus.
- Twigs that enter the phrenic nerve, but do not form plexuses, but end in the diaphragm, pleura and pericardium.
- The branches that form the plexus of the common carotid artery.
- Branches up to the subclavian artery.
Thoracic
The composition of the thoracic sympathetic trunk includes ganglia thoracica (thoracic nodes) - nerve formations of a triangular shape that lie on the costal necks from the sides of the thoracic vertebrae, under the intrathoracic fascia and parietal pleura.
6 main groups of branches depart from the thoracic ganglia:
- White connecting branches that branch off from the intercostal nerves (their anterior roots) and penetrate into the nodes.
- The gray connecting branches emerge from the ganglia and travel to the intercostal nerves.
- The branches of the mediastinum. They originate from the 5 sympathetic superior gangia and pass into the posterior mediastinum, together with other fibers forming the bronchial and esophageal plexuses.
- Nerves of the cardiac chest. They originate from 4-5 sympathetic upper ganglia, participating in the formation of the aortic and deep cardiac plexuses.
- The nerve is large splanchnic. It is assembled from branches of 5-9 sympathetic thoracic nodes and is covered with intrathoracic fascia. Through the holes between the intermediate and medial legs of the diaphragm, this nerve passes into the abdominal cavity and ends in the ganglia of the celiac plexus. This nerve includes a large number of preganglionic fibers (which switch in the ganglia of the celiac plexus to postganglionic fibers), as well as postganglionic fibers that have already switched at the level of the thoracic ganglia of the sympathetic trunk.
- Nerve small intranasal. It is formed by branches of 10-12 nodes. Through the diaphragm, it descends slightly lateral to n. splanchnicus major and is also included in the celiac plexus. Part of the preganglionic fibers of this nerve in the sympathetic ganglia switch to postganglionic, and part goes to the organs.
Lumbar
The lumbar ganglia of the sympathetic trunk are nothing more than a continuation of the chain of ganglia of the thoracic region. The lumbar region includes 4 nodes, which are located on both sides of the spine on the inner edge of the psoas major muscle. On the right side, the nodes are visualized outward from the vena cava inferior, and on the left - outward from the aorta.
The branches of the lumbar sympathetic trunk are:
- White connecting branches from the 1st and 2nd spinal lumbar nerves and going to the 1st and 2nd ganglia.
- Grayconnecting branches. Unites the lumbar ganglia with all spinal lumbar nerves.
- Internal lumbar branches that depart from all ganglia and enter the superior hypogastric, celiac, aortic abdominal, renal and superior mesenteric plexuses.
Sacral department
The lowest section (according to the topography of the sympathetic trunk) is the sacral region, which consists of one unpaired coccygeal node and four paired sacral ganglia. The nodes are located slightly medial to the sacral anterior openings.
Several branches of the sacral section of the sympathetic trunk are distinguished:
- Connecting gray branches to the sacral and spinal nerves.
- The nerves are splanchnic, which are part of the autonomic plexuses in the pelvis. Visceral fibers from these nerves form the hypogastric inferior plexus, which lies on branches from the iliac internal artery, through which sympathetic nerves penetrate the pelvic organs.
