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, th ...
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.
Structure
The sympathetic trunk lies just lateral to the
vertebral bodies 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 chordate ...
. It interacts with the
anterior rami 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 ...
of the
sympathetic nervous system 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 petrou ...
into the skull, and forms a
plexus on the
internal carotid artery; 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 ab ...
.
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 nerve fiber, afferent and Efferent nerve fiber, efferent nerve cell bodies that run along on either s ...
known as
paravertebral ganglia.
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 co ...
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 chordate ...
.
Function
The sympathetic trunk is a fundamental part of the
sympathetic nervous system, and part of the
autonomic nervous system. 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, 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
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
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Sympathetic nervous system