The dorsal root of spinal nerve (or posterior root of spinal nerve or sensory root)
is one of two "roots" which emerge from the
spinal cord. It emerges directly from the spinal cord, and travels to the
dorsal root ganglion
A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dorsa ...
. Nerve fibres with the
ventral root then combine to form a
spinal nerve
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 th ...
. The dorsal root transmits sensory information, forming the
afferent
Afferent may refer to:
Anatomical structures
Meaning "conveying towards a center":
* Afferent arterioles, blood vessels that supply the nephrons
* Afferent lymphatic vessels, lymph vessels that carry lymph to a lymph node
* Afferent nerve fiber ...
sensory
Sensory may refer to:
Biology
* Sensory ecology, how organisms obtain information about their environment
* Sensory neuron, nerve cell responsible for transmitting information about external stimuli
* Sensory perception, the process of acquiri ...
root of a
spinal nerve
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 th ...
.
Structure
The root emerges from the
posterior part of the
spinal cord and travels to the
dorsal root ganglion
A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dorsa ...
. The dorsal root ganglia contain the
pseudo-unipolar cell bodies
The soma (pl. ''somata'' or ''somas''), perikaryon (pl. ''perikarya''), neurocyton, or cell body is the bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus. The word 'soma' comes from the Greek '' σῶΠ...
of the
nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
fibres which travel from the ganglia through the root into the spinal cord.
The
lateral division of the dorsal root contains lightly
myelinated and unmyelinated fibres of small diameter. These carry pain and temperature sensation. These fibers cross through the
anterior white commissure to form the
anterolateral system
The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cor ...
in the
lateral funiculus.
The
medial division of the dorsal root contains
myelinated fibres of larger diameter. These transmit information of discriminative touch, pressure, vibration, and conscious
proprioception originating from spinal levels
C2 through
S5. These fibers are pushed in towards the posterior median sulcus to form the
gracile fasciculus
Gracility is slenderness, the condition of being gracile, which means slender. It derives from the Latin adjective ''gracilis'' (masculine or feminine), or ''gracile'' ( neuter), which in either form means slender, and when transferred for examp ...
and the
cuneate fasciculus of the
posterior column–medial lemniscus pathway.
If the dorsal root of a spinal nerve were severed it would lead to numbness in certain areas of the body.
Additional images
File:Cervical vertebra english.png, Cervical vertebra
File:Medulla spinalis - Section - English.svg, Medulla spinalis
File:Gray675.png, A spinal nerve with its anterior and posterior roots.
File:Gray759.png, The sensory tract.
File:Gray770-en.svg, Diagrammatic transverse section of the medulla spinalis and its membranes.
File:Gray796.png, A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots.
File:Gray799.svg, Scheme showing structure of a typical spinal nerve.
See also
*
Ventral root
References
External links
* - "Superior view of a section through the spinal cord within the
vertebral foramen."
* - "Spinal Root Nerve Fibers"
Dorsal Root - Cell Centered Database
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Back anatomy
Peripheral nervous system