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Typical Spinal Nerve Sanjaya Adikari Department of Anatomy.

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Presentation on theme: "Typical Spinal Nerve Sanjaya Adikari Department of Anatomy."— Presentation transcript:

1 Typical Spinal Nerve Sanjaya Adikari Department of Anatomy

2 Skull Vertebral column CNS is covered by the skull and the vertebral column PNS is outside

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4 Structure of a spinal cord segment Posterior median septum Posterior horn Lateral horn Anterior horn Anterior median fissure Central canal Posterior white column Lateral white column Anterior white column Anterior nerve root Posterior nerve root

5 Dorsal root ganglion Somatic Autonomic

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7 Dorsal and ventral roots Dorsal roots contain afferent (sensory) axons Ventral roots contain efferent (motor) axons The ventral roots continue out from the spinal cord, and mix with their corresponding dorsal nerve root at a point after the ganglion The 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 refers to the mixed spinal nerve It is formed from the dorsal and ventral roots Passes out through the intervertebral foramen There are 31 bilaterally-paired spinal nerves –8 cervical nerves (C1-C8) –12 thoracic nerves (T1-T12) –5 lumbar nerves (L1-L5) –5 sacral nerves (S1-S5) –1 coccygeal nerve (Co)

10 7 12 5 5 8 5 5 1 Vertebral column Spinal cord

11 C2 C1 C4 C3 C6 C5 T1 C7 T3 T2 T5 T4 T7 T6 T9 T8 T11 T10 L1 T12 C1 C8 T3 T10 L1, L2 L3, L4 L5 S, C C1 C7 C8 Spinal nerves T1 T2 T10

12 T12 L1 L2 L3 L4 L5 Sacrum Coccyx Foetus at 3 months T12 L1 L2 L3 L4 L5 Sacrum Coccyx Adult Length of the spinal cord T12 L1 L2 L3 L4 L5 Sacrum Coccyx At birth S2

13 Anterior and posterior primary rami The posterior primary rami have lateral and medial branches They supply – back muscles and skin over the back The anterior primary rami give off anterior and lateral cutaneous branches They supply –the rest of the body wall Anterior primary rami also give rise to the roots of the various nervous plexuses

14 Spinal nerves in the thoracic region Anterior cutaneous branch Lateral cutaneous branch MedialLateral Anterior Posterior These are typical spinal nerves

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16 Gray ramus communicans unmyelinated White ramus communicans myelinated Rami communicantes

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18 Formed by communicating branches between anterior primary rami of spinal nerves. Anterior primary rami form the roots of nerve plexus What are the advantages of a nerve plexus? Last’s Anatomy, 10 th ed. Page 13 Nerve plexus

19 Dermatome Area of skin supplied by a single spinal nerve or spinal cord segment Myotome The muscle/s supplied by a single spinal nerve or spinal cord segment


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