Sympathetic Trunk
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The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the
skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
to the
coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and othe ...
. They are a major component of the
sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
.


Structure

The sympathetic trunk lies just lateral to the
vertebral bodies The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
for the entire length of the
vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
. It interacts with the
anterior rami The ventral ramus (pl. ''rami'') (Latin for ''branch'') is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk (anatomy), trunk and the limbs. They are mainly larger than the dorsal ramus of spinal ...
of
spinal nerves A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...
by way of
rami communicantes Ramus communicans (plural rami communicantes) is the Latin term used for a nerve which connects two other nerves, and can be translated as "communicating branch". Structure When used without further definition, it almost always refers to a commu ...
. The sympathetic trunk permits
preganglionic fibers In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers. All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these f ...
of the
sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
to ascend to spinal levels superior to T1 and descend to spinal levels inferior to L2/3.Greenstein B., Greenstein A. (2002): Color atlas of neuroscience – Neuroanatomy and neurophysiology. Thieme, Stuttgart – New York, . The superior end of it is continued upward through the
carotid canal The carotid canal is a passageway in the temporal bone of the skull through which the internal carotid artery enters the middle cranial fossa from the neck. Structure The carotid canal is located within the middle cranial fossa, at the petrous ...
into the skull, and forms a
plexus In neuroanatomy, a plexus (from the Latin term for "braid") is a branching network of vessels or nerves. The vessels may be blood vessels (veins, capillaries) or lymphatic vessels. The nerves are typically axons outside the central nervous syste ...
on the
internal carotid artery The internal carotid artery (Latin: arteria carotis interna) is an artery in the neck which supplies the anterior circulation of the brain. In human anatomy, the internal and external carotids arise from the common carotid arteries, where these b ...
; the inferior part travels in front of the
coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and othe ...
, where it converges with the other trunk at a structure known as the
ganglion impar The pelvic portion of each sympathetic trunk is situated in front of the sacrum, medial to the anterior sacral foramina. It consists of four or five small sacral ganglia, connected together by interganglionic cords, and continuous above with the a ...
. Along the length of the sympathetic trunk are
sympathetic ganglia The sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous system. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve c ...
known as
paravertebral ganglia The sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous system. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve cel ...
. File:Gray530.png, The sympathetic trunk (yellow) can be seen just
lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...
to the
vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
.


Function

The sympathetic trunk is a fundamental part of the
sympathetic nervous system The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
, and part of the
autonomic nervous system The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control ...
. It allows nerve fibres to travel to spinal nerves that are superior and inferior to the one in which they originated. Also, a number of nerves, such as most of the
splanchnic nerves The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the viscera, innervation of the internal organs), carrying fibers of the autonomic nervous system (visceral efferent fibers) as well as sensory fibers fr ...
, arise directly from the trunks.


Additional images

File:Spinal nerve.svg, The formation of the spinal nerve from the dorsal and ventral roots. File:Gray829.png, Dissection of side wall of pelvis showing sacral and pudendal plexuses. File:Gray837.png, Sacral plexus of the right side. File:Gray839.png, Diagram of efferent sympathetic nervous system. File:Gray840.png, Sympathetic connections of the ciliary and superior cervical ganglia. File:Sacral sympathetic.jpg, Sacral sympathetic


See also

*
Horner's syndrome Horner's syndrome, also known as oculosympathetic paresis, is a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged. The signs and symptoms occur on the same side (ipsilateral) as it is a lesion ...


References


External links

* - "The position of the right and left vagus nerves, and sympathetic trunks in the mediastinum." * - "The Female Pelvis: The Posterolateral Pelvic Wall" * - "Autonomic Connections of the Spinal Cord"
Diagram at umm.edu
{{Authority control Sympathetic nervous system