Dorsal & Ventral Roots Formation

Cyclostomes

sensory and motor roots do NOT join together

lampreys

in cyclostomes, remain separate and emerge alternately from the spinal cord

hagfishes

in cyclostomes, there may be an incomplete union

fishes

dorsal sensory root and ventral motor root unite with each other outside the vertebral column to form a common trunk

amphibians

dorsal and ventral roots of spinal nerve unite in their passage through the intervertebral foramen

mammals

complicated plexuses from intermixing fibers from the ventral branches of spinal nerves are found divides into three branches or rami

dorsal ramus

in mammals, supplying skin and muscles of the back

ventral ramus

in mammals, body muscles and skin of ventral side

communicating ramus

in mammals, communicants or visceral ramus going to the viscera and ganglion of the autonomic NS

mammals

dorsal and ventral roots of spinal nerve unite in their passage within the neural canal like amniotes