Spinal Cord

SPINAL CORDACHMAD AMINUDDIN

PROTECTIVE STRUCTURESBONY VERTEBAEFAT AND CONNECTIVE TISSUEIN THE EPIDURAL SPACECONNECTIVE TISSUE MENINGE - DURAMATER - ARACHNOID MATER. - PIAMATERCEREBROSPINAL FLUID IN THE SUBARACHNOID SPACE

SPINAL CORDSpinal cord is the major reflex center and conduction pathway between the body and the brainThe spinalcord is 42 45 cm long and extends from the foramen magnum to the level of the L1 or L2 vertebra.The cervical enlargement, extends from the C4 through T1 segment ao spinal cord, and most of the anterior rami of the spinal nerve arising from it form the brachial plexus of nerve.Lumbosacral enlargement, extends from T11 through S1 segmen of the spinal cord

Fig 4.22

SPINAL NERVESSpinal nerve initially arise from the spinal cord as a rootlets, which converge toform two nerve roots. 1. An antrior ( ventral ) root, consisting of motor fibers passing from nerve cell bodies in the anterior horn of spinal cord gray matter to effector organs 2. A posterior ( dorsal ), consisting of senso ry fibers passing from nerve cell bodies in the spinal sensory root ganglon,that extend peripherally to sensory endings and centrally to the posterior horn ofspinal cord

SPINAL NERVESThe posterior and anterior nerve roots unite, within or just proximal to the intervertebral foramen, to form a mixed spinal nerve, which immediately divides into two primary rami : a posterior ramus and anterior ramus.A branches of the mixed spinal nerve, the posterior and anterior rami carry both motor and sensory fibers

Fig 1.32

fig 13.3

fig 13.12

POSTERIOR COLUMNConveys nerve impulses for the sensation of fine touch, stereognosis, conscious proprioception, kinesthesia, weight discrimination and vibration.Axons of first-order neurons from one side of the body form the posterior column on the same side and end in the medulla,where they sinapse with denrites and cell bodies of second-order neurons.Axons of second-order neurons decussate, enter the medial lemniscus on the opposite side , and extend to the thalamus.Third-order neurons transmit nerve impulses from the thalamus to the primary somatosensory cortex on the side opposite the site of stimulation

LATERAL SPINOTHALAMIC TRACTConveys nerve impulses for pain and thermal sensation.Axons of first-order neurons from one side of the body synapse with dendrites and cell bodies of second-order neurons in the posterior gray horn on the same side of the body.Axons of second-order neurons decussate, enter the lateral spinothalamic tract on the opposite side, and extend to the thalamus.Third-order neurons transmit nerve impulses from the thalamus to the primary somatosensory cortex on the side opposite the site of stimulation.

ANTERIOR SPINOTHALAMIC TConveys nerve impulses for itch, tickle, pressure, and crude, poorly localized touch sensation.Axons of first-order neurons from one side of the body synapse with dendrites and cell bodies of second-order neurons in the posterior gray horn on the same side of the body.Axons of second-order neurons decussate, enter the anterior spinothalamic tract on the opposite side, and extend to the thalamus.Third-order neurons transmit nerve impulses from the thalamus to the primary somatosensory cortex on the side opposite the site of stimulation.

ANTERIOR AND POSTERIOR SPINOCEREBELLAR TRACTSConvey nerve impulses from proprioceptors in the trunk and lower limb of one side of the body to the same side of the cerebellum.The proprioceptive input inform the cerebellum of actual movements, allowing it to coordinate,smooth, and refine skilled movements and maintain posture and balance.

DESCENDING PATHWAYSThe direct pathways - Lateral coticospinal tract - Anterior corticospinal tract - Corticobulbar tract Destined to cause precise, voluntary movement of skeletal muscles.The indirect patways

DESCENDING PATHWAYSThe indirect pathways - Rubrospinal tract. - Tectospinal tract. - Vestibulospinal tract. They convey nerve impulses from the brain stem and other parts of the brain that govern automatic movements and help coordinate body movements with visual stimuli. Maintain skeletal muscle tone, maintain contraction of postural muscles, and play a major role in equilibrium by regulating muscle tone in response to movement of the head.

fig 13.13

TRANSECTION OF THE SPINAL CORDC1 C3 : Patient has no function below head level ; a ventilator is required to maintain respiration.C4 C5 : Respiration occur, but the patient is quadriplegic.C6 C8 : The patient experiences a loss of hand and a variable amount of upper limb function ; the individual may be able to self-feed or propel a wheelchair.

TRANSECTION OF THE SPINAL CORDT1 T9 : ( between cervical and lumbosacral enlargement ) : The individual is paraplegic ; the amount of trunk control varies with the height of the lesion.T10 T11 : The patient has some thigh muscle function, which may allow walking with long leg braces.L2 L3 : The individul retains most leg muscle function ; short leg braces may be required for walking.

VASCULATURE OF THE SPINAL CORD AND SPINAL ROOTSThe teries supplying the spinalcord are branches of - Vertebral a - Ascending cervical a - Deep cervical a - Intercostal a - Lumbar a - Lateral sacral aThree longitudinal arteries - Anterior spinal artery - Paired posterior spinal arteries.

Fig 4.28

ANTERIOR AND POSTERIOR SEGMENTAL MEDULLARY AAre derived from spinal branches of - Ascending cervical a - Deep cervical a - Vertebral a - Posterior intercostal a - Lumbar a.

VASCULATURE OF THE SPINAL CORDThe great anterior segmental medullary artery - On the lft side in about 65 % of people - Reinforced the spinal cord circulation. - Arise from an inferior intercostal or upper lumbar arteryPosterior and anterior radicular arteries - Are small and supply only the nerve roots.

VEINS OF THE SPINAL CORDThere are 3 anterior 3 posterior spinal veins, drained by 12 anterior and posterior medullary and radicular veins, then joinThe internal vertebral ( epidural ) venous plexus, pass superiorlyThrough the foramen magnum to communi cate with dural sinus and vertebral veins in the cranium.The internal vertebral plexus also communicate with the external vertebral venous plexus, on theexternal surface of the vertebrae.

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Spinal Cord