C6 segment of spinal cordSpinal ganglionDermatomyotomeAutonomous region(where overlap ofdermatomes isleast likely)of C6 dermatome(pad of thumb)Skin on the lateral side of the forearm and on thethumb is innervated by C6 spinal level (spinal nerve).The dermis of the skin in this region develops from the somiteinitially associated with the C6 level of the developing spinal cordCaudalCranialSomite
Fig. 1.37 Myotomes.
C6 segment of spinal cordMuscles that abduct the arm are innervated by C5 and C6 spinal levels (spinal nerves) and develop from somites initially associated with C5 and C6 regions of developing spinal cordC5 segment of spinal cordDermatomyotomeSomite
Fig. 1.38 Dermatomes. A. Anterior view. B. Posterior view.
Fig. 1.39 Development of the visceral part of the nervous system.
Motor nerve endingassociated withblood vessels,sweat glands,arrector pili musclesat peripheryPart of neural crest developinginto spinal gangliaVisceral motor ganglionMotor nerve ending associated with visceraDeveloping gastrointestinal tractSensory nerve endingBody cavity(coelom)Visceral sensory neuron developsfrom neural crest and becomespart of spinal ganglionVisceral motorpreganglionicneuron in lateralregion of CNS(spinal cord)Postganglionic motor neuron is outside CNS.An aggregation of postganglionic neuronal cellbodies forms a peripheral visceral motor ganglion.
Fig. 1.40 Basic anatomy of a thoracic spinal nerve.
Fig. 1.41 Parts of the CNS associated with visceral motor components.
SympatheticT1 to L2spinal segmentsBrainstemcranial nervesIII, VII, IX, XS2 to S4spinal segmentsParasympathetic
Fig. 1.42 Sympathetic part of the autonomic division of the PNS.
Abdominal visceraHeartOrgansPeripheralSympathetic nerves followsomatic nerves to periphery(glands, smooth muscle)Pelvic visceraGanglion imparEsophageal  plexusPrevertebral plexus
Fig. 1.43 Course of sympathetic fibers that travel to the periphery in the same spinal nerves in which they travel out of the spinal cord.
Gray ramus communicansT10 spinal nervePosteriorramusAnteriorramusPeripheral distribution of sympatheticscarried peripherally by terminal cutaneousbranches of spinal nerve T1 to L2Motor nerve to sweat glands,smooth muscle of bloodvessels, and arrector pilimuscles in the part of T10dermatome supplied by theanterior ramusT10 spinal segmentWhite ramus communicans
Fig. 1.44 Course of sympathetic nerves that travel to the periphery in spinal nerves that are not the ones through which they left the spinal cord.
Sympathetic paravertebral trunksPeripheral distribution ofascending sympatheticsPeripheral distribution ofdescending sympathetics(C1) C2 to C8T1 to L2L3 to CoWhite ramus communicansGray ramus communicansPosterior rootGray ramus communicansGray ramus communicansAnterior root
Fig. 1.45 Course of sympathetic nerves traveling to the heart.
Sympathetic cardiac nervesSympathetic cardiac nervesSympathetic trunkCardiac plexusT1 to T4CervicalWhite ramuscommunicansGray ramuscommunicans
Fig. 1.46 Course of sympathetic nerves traveling to abdominal and pelvic viscera.