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SPINAL CORD

2. DefinitionAn elongated and almost cylindrical part of the central nervous systemIt is suspended in the vertebral canal It is surrounded by the meninges and CSFAbove, it is continuous with the medulla oblongataExtends from the upper border of atlas to the lower border of the 1st lumbar ver

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SPINAL CORD

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    2. 2 Definition An elongated and almost cylindrical part of the central nervous system It is suspended in the vertebral canal It is surrounded by the meninges and CSF Above, it is continuous with the medulla oblongata Extends from the upper border of atlas to the lower border of the 1st lumbar vertebra 45 cm As thick as a little finger Link between the brain and the rest of the body

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    4. 4 Structure Incompletely divided into two equal parts by fissures Anteriorly fissure : shallow Posteriorly : deep narrow septum - posterior median septum Grey matter in the centre White matter in the surrounding supported by neurogila

    5. 5 Grey matter H shaped arrangement Two anterior, two posterior and two lateral horns Central transverse portion is called the transverse commissure Central commissure contains the spinal canal containing CSF Grey matter contains sensory cells, lower motor neurone cells and connector neurones linking sensory and motor neurones spinal reflexes Where an impulse passes from one nuerone to another neurone the junction is called a synapse and there is a chemical transmitter

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    7. 7 Posterior columns of grey matter Composed of cell bodies of the lower motor neurones Which are stimulated by upper motor neurone fibres Or by the cell bodies of connector neurones (reflex arc) The posterior root ganglia (spinal ganglia) Cell bodies lie outside the cord On the pathway of sensory nerves All sensory nerves pass through these ganglia

    8. 8 White matter Arranged in three columns or tracts anterior posterior lateral these tracts are formed by sensory nerve fibres ascending to the brain motor nerve fibres descending from the brain fibres of connector neurones

    9. 9 Spinal Nerves 31 pairs of spinal pass through the intervertebral foramina Each spinal nerve is formed by the union of anterior and posterior roots as soon as they come out of the intervertebral foramina

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    16. 16 MRI Spinal Cord

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    18. 18 Reflex Action

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    27. 27 Blood supply of the spinal cord: Branches of the vertebral, deep cervical, intercostal, and lumbar arteries contribute to three arteries that run the length of the spinal cord; Anterior spinal artery Two posterior spinal arteries. The anterior spinal artery arises at the level of the foramen magnum by the junction of two branches, one from each vertebral artery. Each posterior spinal artery arises from the posterior inferior cerebellar artery at the same level.

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    30. 30 Generally the proportion of flow is greatest from the raducularis magna feeder artery to the thracolumbar region. In abnormal situations ( e.g. high take-off) the iliac artery branch may supply the lower thoracolumbar region of the cord entering by way of the intervertebral foramen in the vicinity of L4-5

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    33. 33 21 pairs of segmental radicular arteries supply the nerve roots Half of them contribute to the spinal arteries. The largest is the great anterior radicular artery of Adamkiewicz (radicularis magna), It supplies the lower thoracic and upper lumbar parts of the cord. It usually arises from a lower intercostal or a high lumbar artery anywhere between L4 & T8 It makes a major contribution Spinal injury or aortic surgery may compromise the blood supply of the lower part of the spinal cord. The other segmental radicular arteries are small

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    36. 36 Venous drainage Venous drainage of the spinal cord is by internal and external venous plexuses Anterior sulcal vein Posterior sulcal vein And thence to the vertebral veins, intercostal veins and lumbar veins

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