4 Structure of a spinal cord segment Posterior median septumPosterior hornLateral hornAnterior hornAnterior median fissureCentral canalPosterior white columnLateral white columnAnterior white columnAnterior nerve rootPosterior nerve root
7 Dorsal and ventral roots Dorsal roots contain afferent (sensory) axonsVentral roots contain efferent (motor) axonsThe ventral roots continue out from the spinal cord, and mix with their corresponding dorsal nerve root at a point after the ganglionThe combined dorsal and ventral roots are called a spinal nerve (therefore, spinal nerves are mixed).
8 Spinal nerve is mixed (motor + sensory + autonomic)
9 Spinal nerve is mixed (motor + sensory + autonomic) Spinal nerve refers to the mixed spinal nerveIt is formed from the dorsal and ventral rootsPasses out through the intervertebral foramenThere are 31 bilaterally-paired spinal nerves8 cervical nerves (C1-C8)12 thoracic nerves (T1-T12)5 lumbar nerves (L1-L5)5 sacral nerves (S1-S5)1 coccygeal nerve (Co)
12 Length of the spinal cord SacrumCoccyxFoetusat 3 monthsT12L1L2L3L4L5SacrumCoccyxAt birthS2T12L1L2L3L4L5SacrumCoccyxAdult
13 Anterior and posterior primary rami The posterior primary rami have lateral and medial branchesThey supplyback muscles and skin over the backThe anterior primary rami give off anterior and lateral cutaneous branchesthe rest of the body wallAnterior primary rami also give rise to the roots of the various nervous plexuses
14 Spinal nerves in the thoracic region Anterior cutaneous branchLateral cutaneous branchMedialLateralAnteriorPosteriorThese are typical spinal nerves
18 Nerve plexusFormed by communicating branches between anterior primary rami of spinal nerves.Anterior primary rami form the roots of nerve plexusWhat are the advantagesof a nerve plexus?Last’s Anatomy, 10th ed.Page 13
19 DermatomeArea of skin supplied by a single spinal nerve or spinal cord segmentMyotomeThe muscle/s supplied by a single spinal nerve or spinal cord segment
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