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Extends from the foramen magnum to L1 or L2Conus medularis - it is the end of the spinal
cord Denticulate ligaments – pia mater attaching the
spinal cord t the vertebral wallFilum terminale – pia mater extension from the
conus medularis to the coccix
Anatomy of the Spinal Cord
3
Lumbar tap – removal of CSF from the vertebral canal bellow L3
Cervical and lumbar enlargements31 pairs of spinal nerves leave the spinal cordCauda equina – collection of spinal nerves at
the end of the spinal cord
Anatomy of the Spinal Cord
4
Spinal meninges
Three layersDura mater
Single layerEpidural space – between the vertebra
and dura. Filled with fat and blood vessels
ArachnoidSubarachnoid space – between
arachnoid and pia. Filled with CSFPia mater
6
Structures of the spinal cord
Gray Matter Cell bodies, unmyelinated axons,
dendrites and neurogliaPosterior or dorsal horns – interneurons
and sensory fibers coming from the dorsal root ganglion
Anterior or ventral horns – cell bodies of the somatic motor neurons that send their axons to the ventral root
9
Lateral gray horns contain visceral motor neurons
Gray commissures contain axons that cross from one side to the other
Central canal – filled with CSF
Gray matter
10
White matter
Divided into six columns (funiculi) containing tracts
Posterior funiculiPosterior median sulcus
Anterior funiculiAnterior median fissure
Lateral funiculi
11
8 pairs of cervicalAbove C7 all nerves emerge above the
corresponding vertebraC8 emerge between C7 and T1
12 pairs of thoracic5 pairs of lumbar5 pairs of sacralI pair of coccygeal
31 pairs of spinal nerves (mixed)
13
OriginDorsal root and dorsal root ganglionVentral root
Dorsal ramus sensory and motor innervation to the skin
and muscles of the back
Spinal nerves
14
Spinal nerves
Ventral ramus sensory and motor to the ventrolateral
body surface, body wall and limbsT2 – T12 form intercostal nervesAll other will form plexuses
15
Complex interwoven network of nervesFour large plexuses
Cervical plexusBrachial plexusLumbar plexusSacral plexus
Nerve plexus
16
The Cervical Plexus
Ventral rami of spinal nerves C1 to C5Innervate muscles of the neckInnervate the diaphragm
Phrenic nerve (C3, C4,C5)
18
The Lumbar Plexus
Lower abdominopelvic region and the anterior thigh
L1 – L4Femoral Nerve
Anterior muscles of femoral areaObturator Nerve
Adductors of leg
27
The Sacral Plexus
Posterior thigh, gluteal region, leg and footL4 – S4Sciatic nerve
Tibial nerveCommon fibular nerve
Pudendal nerveMuscles and skin of perineum
28
Reflexes are rapid and predictable automatic responses to stimuli
Neural reflex involves sensory fibers to CNS and motor fibers to effectors
Spinal Reflexes
Five components Receptor – it is the site of the stimulus Sensory neuron – transmits the stimulusIntegration Center
Monosynaptic reflexPolysynaptic reflex
Motor neuron - conducts the impulse to the effector
Effector – muscle or gland
Reflex arc
Somatic ReflexesSpinal Reflexes
Patellar (knee-jerk)Achilles Triceps Biceps etc.
Reflex classification
Reflex classification
Superficial reflexes Plantar reflex
• Normal response – curling the toe• Abnormal response – Babisnki’s sign
Corneal reflex - Cranial nerve VGag reflex
• Cranial nerves IX and X