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The dorsal root of spinal nerve (or posterior root of spinal nerve or sensory root) [1] 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. Nerve fibres with the ventral root then combine to form a spinal nerve.
A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion [1]) 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 dorsal root ganglia. [2] The axons of dorsal root ganglion neurons are known as afferents.
A dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. Note the axons growing out of the ganglion. A ganglion (pl.: ganglia) is a group of neuron cell bodies in the peripheral nervous system.
The body is situated in the dorsal root ganglion, with one axon traveling peripherally to tissue, and one traveling into the dorsal column. On the right is a bipolar neuron. When an action potential is generated by a mechanoreceptor in the tissue, the action potential will travel along the peripheral axon of the first-order neuron.
This is in contrast with the dorsal spinocerebellar tract (C8 - L2/L3), which only has 1 unilateral axon that has its cell body in Clarke's column (only at the level of C8 - L2/L3). Originates from ventral horn at lumbosacral spinal levels. Axons first cross midline in the spinal cord and run in the ventral border of the lateral funiculi.
Ventral root axons join with dorsal root ganglia to form mixed spinal nerves (below). These then merge to form peripheral nerves. Shortly after this spinal nerve forms, it then branches into the dorsal ramus and ventral ramus. Spinal nerves are mixed nerves that carry both sensory and motor information.
These rami also contain general visceral afferent fibers (sensory from the organs) whose primary cell bodies reside dorsal root ganglia (which then synapse in the dorsal horn). The preganglionic sympathetic fibers will enter into the sympathetic trunk and either synapse at the ganglion on the same level, or travel up or down the sympathetic ...
Opposing gradients of such morphogens as BMP and SHH form different domains of dividing cells along the dorsal ventral axis. [15] Dorsal root ganglion neurons differentiate from neural crest progenitors. As the dorsal and ventral column cells proliferate, the lumen of the neural tube narrows to form the small central canal of the spinal cord. [16]