1. .Anatomy and physiology ofspinal cord, ventricle and CSFkendeneh B.(R1)october 16, 2013

2. .Out lineAnatomy of spinal cordPhysiology of spinal cordAnatomy of ventriclesPhysiology of CSF 3. objectives To know basic anatomy of sp. Cord To understand the position of the main nervepathways and nerve cell groups in the spinal cord To review basic structure of ventricle and to learnhow CSF produced 4. Spinal cord It stretches from upper border of the foramenMagnum to the intervertebral disc between thefirst and second lumbar vertebrae. In the newborns, it extends to the level of thethird lumbar vertebraDue to the differential growth of the vertebralcolumn relative to the spinal cord, the spinal cordsegments do not always correspond to thevertebral levels. 5. Accordingly, the cervical spinal nerves exit abovetheir corresponding vertebrae the remaining spinal nerves emerge from thevertebral column below the correspondingvertebrae.When the dorsal and ventral roots of the lowerlumbar and sacral segments assume a longercourse around the conus medullaris to reach thecorresponding intervertebral foramina, the caudaequina is formed 6. Spinal cord meniges is invested by the dura, arachnoid, and the piamater. The dura mater is comprised of an innermeningeal and an outer endosteal layer.The outer endosteal layer forms the periosteum ofthe vertebral canal and the epineurium of thespinal nerves at or slightly beyond theintervertebral foramina. 7. . At the level of the second sacral vertebra thespinal dura joins the filum terminale to attach tothe coccyx as the coccygeal ligament.The epidural space contains the internal vertebralplexus 8. .The arachnoid mater is a loose, irregular, andtrabecular layer that is continuous with cranialarachnoid mater. surrounds the spinal cord without following thesulci. is pierced by vessels that supply the pia mater. 9. .The pia mater It intimately adheres to the spinal cord, giving riseto the dentate ligaments These ligaments are triangular extensions thatextend to the dura, coursing between the dorsaland ventral roots. act as suspensory ligaments for the spinal cord 10. . 11. Blood supply of spinal cord 12. Arteries of the Spinal Cord and Nerve Rootsare branches of the vertebral, ascending cervical,deep cervical, intercostal, lumbar, and lateralsacral arteries Three longitudinal arteries supply the spinal cord:- an anterior spinal artery- paired posterior spinal arteries.The anterior spinal artery, formed by the union ofbranches of the vertebral arteries 13. Arteries of the Spinal Cord and Nerve Roots contd Sulcal arteries arise from the anterior spinal arteryand enter the spinal cord through this fissure. Each posterior spinal artery is a branch of eitherthe vertebral artery or the posteroinferiorcerebellar artery.The posterior spinal arteries commonly formanastomosing channels in the pia mater. 14. . 15. Arteries of the Spinal Cord and Nerve Roots contdThe anterior and posterior segmental medullary arteries .The segmental medullary arteries are located chiefly wherethe need for a good blood supply to the spinal cord isgreatest. They enter the vertebral canal through the IV foramina 16. Blood supply of vertebrae and spinal cord 17. ,Veins of the Spinal Cord have a distribution similar to that of the spinal arteries. There are usually three anterior and three posterior spinalveins . The veins draining the spinal cord join the internalvertebral (epidural) venous plexus in the epidural space . The internal vertebral venous plexus communicate withdural sinuses and vertebral veins in the cranium. The internal vertebral plexus also communicates with theexternal vertebral venous plexus on the external surface ofthe vertebrae. 18. . 19. Internal organization Each spinal segment consists of central gray andperipheral white matters that are connected by thecorresponding gray and white commissures. The central canal is a tube that pierces the graycommissure of the spinal cord 20. A. Gray matter consist of nerve cells & unmyelinated nerve fibers H-shaped formed of: anterior horns: containing motor nuclei. poster horns: containing sensory nuclei lateral horns containing autonomic cells 21. . 22. I. Nuclei of the posterior horn1. Substatia gelatinosa situated at the apex of the posterior gray columnthroughout the length of the spinal cordreceives afferent fibers concerned with pain,temperature, & touch impulses via central processes ofdorsal root ganglion cellsits axons cross to the opposite side in the whitecommissure & ascend in lat. white matter as the lat.spinothalamic tract 23. Nuclei of the posterior horn contd2. Nucleus Proprius Situated in the middle part of the post horn anterior to thesubstantia gelatinosa throughout the spinal cord receives fibers from the posterior white column that areassociated with the senses of position & movement, two-pointdiscrimination, & vibration. its axons cross to the opposite side in the white commissurethen ascend in the ant white matter as ant. spinothalamictract 24. .3. Clarks/ dorsal nucleus situated at the base of the posterior gray column inthe thoracic & upper lumbar region onlyThe cells are associated with proprioceptive impulsesIts axons ascend in the lat. column of the same sideforming the posterior spinocerebellar tract 25. II. Nuclei of the anterior horn (motor)are grouped into 3 groups of motor nuclei1. Medial group: ventromedial & dorsomedial nuclei - found in allsegments of the spinal cord responsible for innervating the skeletal muscles of theneck & trunk. 26. . Nuclei of the anterior horn contd2. Lateral group: ventrolateral & dorsolateral nuclei - present in the cervical& lumbosacral segments of the cord & responsible forinnervating the skeletal muscles of the limbs3. Central group: present in some cervical & lumbosacral segments phrenic nucleus (C3-C5 segments) efferents supplyingthe diaphragm accessory nucleus (C1-C5/6 segments) 27. III. Nuclei of the lat. horn (autonomic)Formed by the intermediolateral group of cells1) SympatheticPresent in the lat. horns of the segment from T1 toL2/3its axons leave the cord through the ventral roots ofthe corresponding nerves as preganglionic fibers2) ParasympatheticPresent in the lat. horn of the S2,3,&4 spinal segmentsgive rise to preganglionic parasympathetic fiberswhich relay in peripheral ganglia in the organ supplied 28. B. White Matter It is divided into 3 large columns on each side Posterior column: lies b/n the post median septum & theattachment of the dorsal nerve root it contains ascending tracts only Lateral column: lies b/n the attachments of the dorsal &ventral nerve roots. It contains both ascending & descending tracts. Anterior column: lies b/n the ant. median fissure & theattachment of the ventral nerve roots. It contains descending tracts mainly. 29. . 30. PATHWAYS IN WHITE MATTER the white matter contains 3 types of nerve fibres Ascending (sensory) tracts: carrying sensory impulsesfrom the spinal cord to higher centers Descending or efferent tracts: carrying motor orautonomic impulses from higher centres to the spinalcord. Associative tracts: containing short ascending &descending fibres which coordinate the function of thedifferent regions of spinal cord 31. Descending tractsFunction maintenance of posture and balance, control of visceral and somatic reflex activity andmuscle tone modification of the sensory signals 32. Descending Fiber SystemsUpper Motor Neurons Are the nerve fibers that descend in the white matterfrom different supraspinal nerve centers provide numerous separate pathways that caninfluence motor activity.Lower Motor Neurons Are the motor neurons situated in the anterior graycolumns of the spinal cord sending axons to innervateskeletal muscle constitute the final common pathway to the muscles. 33. ,Descending pathwayA. Corticospinal Tract Arises from the cerebral cortexPathways is a large bundle of myelinated axons thatdescends through the brain stem via a tract calledthe medullary pyramid and then largely crossesover downward into the lateral white columns. 34. . The great majority ofaxons in thecorticospinal systemdecussate in thepyramidal decussationwithin the medulla anddescend within thelateral corticospinaltract These fibers terminatethroughout the ventralgray column and at thebase of the dorsalcolumn. 35. Corticospinal tracts 36. .Function of cortico-spinal tract- concerned with voluntary, discrete, skilled movements,especially those of the distal parts of the limbsB. Rubrospinal tract: Arises from the red nucleus & crosses to the opposite side Descends in the lat. column of the spinal cordFunction: relays impulses from the corpus striatum & cerebellum tothe A.H.Cs of the spinal cord facilitates the activity of flexor muscles & inhibits theactivity of extensor or antigravity muscles 37. Rubrospinal tract 38. .C. Tectospinal Tract: Arises from the sup. colliculus of midbrain Crosses to the opposite side Descends in the ant. column of the spinal cordFunction concerned with reflex postural movements in response tovisual stimuli 39. Tectospinal tract 40. .D. Vestibulospinal Tract Arises from the lat-vestibular nucleus in the pons majority of its fibres are uncrossed Descends in the ant. column of the spinal cordFunction: facilitates the activity of the extensor muscles, inhibitsthe activity of the flexor muscles, & is concerned withthe postural activity associated with balance. 41. Vestibulospinal tract 42. Ascending tracts of the spinal cordAnatomical organization General information from the peripheral sensory endings isconducted through the nervous system by a series ofneurons. The ascending pathway to consciousness consists of a threeneuron chain:1. The first-order neuron has its cell body in the posterior root ganglion of thespinal nerve. A peripheral process connects with a sensory receptorending, whereas a central process enters the spinal cordthrough the posterior root to synapse on the second-orderneuron. 43. .2. The second-order neuron gives rise to an axon that decussates & ascends toa higher level of the central nervous system,where it synapses with the third-order neuron3. The third-order neuron is usually in the thalamus & gives rise to aprojection fiber that passes to a sensory region ofthe cerebral cortex 44. Simplest form of the ascending sensory pathway from the sensorynerve ending to the cerebral cortex 45. Ascending Pathways1.Lateral Spinothalamic TractThe pain and thermal receptors in the skin andother tissues are free nerve endings.Painful and thermal sensations ascend in thelateral spinothalamic tract 46. Pain & temperature pathways 47. .2.Anterior Spinothalamic TractThe axons enter the spinal cord from the posteriorroot ganglion and proceed to the tip of theposterior gray column where they divide intoascending and descending branchesthese fibers of the first-order neuron terminate bysynapsing with cells in the substantia gelatinosagroup in the posterior gray columnTransmit impulses from light touch & pressurereceptor 48. .Light/crude touch &pressurepathways 49. .3. posterior White Column:Fasciculus Gracilis and Fasciculus CuneatusThe axons enter the spinal cord from the posteriorroot ganglion and pass directly to the posteriorwhite column of the same side.Here, the fibers divide into long ascending andshort descending fiber these short descending fibers are involved withintersegmental reflexesFor discriminative Touch, Vibratory Sense, andConscious Muscle Joint Sense 50. ..Many of the long ascending fibers travel upward in theposterior white column as the fasciculus gracilis andfasciculus cuneatus.The fasciculus gracilis is present throughout thelength of the spinal cord and contains the longascending fibers from the sacral, lumbar, and lower sixthoracic spinal nerves.The fasciculus cuneatus contains the long ascendingfibers from the upper six thoracic and all the cervicalspinal nerves. 51. .The fibers of the fasciculus gracilis and fasciculuscuneatus ascend ipsilaterally terminate by synapsing on the second-orderneurons in the nuclei gracilis and cuneatusThe axons of the second-order neurons decussatewith the corresponding fibers of the opposite sidein the sensory decussation.The fibers then ascend as a single compact bundle,the medial lemniscus, through the medullaoblongata, the pons, and the midbrain 52. . Many fibers in the fasciculus cuneatus from thecervical and upper thoracic segments, havingterminated on the second-order neuron of thenucleus cuneatus, are relayed and travel as theaxons of the second-order neurons to enter thecerebellum. The pathway is referred to as the cuneocerebellartract 53. .4. Posterior Spinocerebellar Tract The axons enter to the posterior gray column andterminate by synapsing on the second-order neuronsat the base of the posterior gray column. The axons of the second-order neurons enter theposterolateral part of the lateral white column on thesame side and ascend as the posterior spinocerebellartract to the medulla oblongata. Here, the tract joins the inferior cerebellar peduncleand terminates in the cerebellar cortex to transmite muscle and Joint Sense impulse to theCerebellum 54. . The posterior spinocerebellar fibers receive musclejoint information from the muscle spindles,tendon organs, and joint receptors of the trunkand lower limbs. 55. .5.Anterior Spinocerebellar Tract The axons terminate by synapsing with the second-orderneurons in the nucleus dorsalis at the base of the posterior graycolumn . The majority of the axons of the second-order neurons cross tothe opposite side ascend as the anterior spinocerebellar tract in the contralateralwhite column; the minority of the axons ascend as the anterior spinocerebellartract in the lateral white column of the same side . enter the cerebellum through the superior cerebellar peduncle 56. Unconscious muscle joint sense pathways to the cerebellum. 57. Anatomy of the ventricle1. Lateral Ventricles There are two large lateral ventricles, and one ispresent in each cerebral hemisphere. may be divided into a body, which occupies theparietal lobe and from which anterior, posterior,and inferior horns extend. 58. . 59. . 60. .-The body of the lateralventricle extends from theinterventricular foramenposteriorly as far as theposterior end of thethalamus.The body of the lateralventricle has a roof, a floor,and a medial wallThe roof - undersurface ofthe corpus callosum .The floor - the body of thecaudate nucleus and thelateral margin of thethalamusThe medial wall- septumpellucidum 61. .Choroid Plexus of the Lateral Ventricle projects into the ventricle on its medial aspect is a vascular fringe composed of pia mater covered withthe ependymal lining of the ventricular cavity. The blood supply of the choroid plexuses is derivedfrom the choroidal branches of the internal carotidand basilar arteries. The venous blood drains into the internal cerebralveins=> the great cerebral vein=> joins the inferiorsagittal sinus to form the straight sinus. 62. .coronal section ofthe third andlateral ventricles atthe site of theinterventricularforamina showingthe structure of thetela choroidea andits relationshipwith the ependymaand pia mater 63. .2. Third Ventricle is a slitlike cleft between the two thalami. It communicates- anteriorly with the lateral ventricles and- posteriorly with the fourth ventricleBoundaryThe anterior- a thin sheet of gray matter, the lamina terminalisand ant. commissure 64. .The posterior wall is formed by the opening into the cerebral aqueduct. Superior to this opening is the small posteriorcommissureThe lateral wall is formed by the medial surface of the thalamussuperiorly and the hypothalamus inferiorlyThe superior wall is formed by a layer of ependyma that is continuouswith the lining of the ventricle 65. .The inferior wall is formed by the optic chiasma, the tubercinereum, the infundibulum and the mammillarybodies 66. Sagittal section of the brain showing the medial surfaceof the diencephalon 67. .3. Fourth Ventricleis a tent-shaped cavity filled with cerebrospinal fluid.is situated anterior to the cerebellum and posterior tothe pons and the superior half of the medullaoblongata.It is lined with ependyma The fourth ventricle possesses:- lateral boundaries- a roof- rhomboid-shaped floor. 68. .Lateral Boundaries The caudal part by the inferior cerebellarpeduncle and the cranial part by the superiorcerebellar peduncle.Posterior Wall The tent-shaped roof projects into the cerebellum.The superior part is by the medial borders of thetwo superior cerebellar peduncles and the superiormedullary velum 69. . The inferior part of the roof is formed by theinferior medullary velumFloor is formed by the posterior surface of the pons andthe cranial half of the medulla oblongata 70. . 71. Cerebrospinal Fluid The cerebrospinal fluid is found in the ventriclesof the brain and in the subarachnoid space aroundthe brain and spinal cord 72. The Physical Characteristics and Composition of theCerebrospinal Fluid 73. .Functions of CSFserves as a cushion between the central nervoussystem and the surrounding bones, thusprotecting it against mechanical trauma.it provides mechanical buoyancy and support forthe brain. assist in the regulation of the contents of theskull. 74. . 75. .Formation of CSF The cerebrospinal fluid is formed mainly in thechoroid plexuses of the lateral, third, and fourthventricles production of cerebrospinal fluid is not pressureregulated 76. .Circulation of CSF The circulation begins with its secretion from thechoroid plexuses in the ventricles. aided by the arterial pulsations of the choroidplexuses and by the cilia on the ependymal cellslining the ventricles. 77. .Absorption of CSF The main sites are the arachnoid villi that projectinto the dural venous sinuses The arachnoid villi tend to be grouped together toform elevations known as arachnoid granulations. Structurally, each arachnoid villus is adiverticulum of the subarachnoid space 78. . 79. summary SP. cord stretches from upper border of theforamen Magnum to the intervertebral discbetween the first and second lumbar vertebraeand occupy 2/3 of upper vertebra is invested by the dura, arachnoid, and the piamater Both pia and arachnoid mater form theleptomeninges, and they continue around thespinal nerves as perineurium 80. Summary contd Three longitudinal arteries supply the spinal cord The veins draining the spinal cord join the internalvertebral venous plexus in the epidural space Each spinal segment consists of central gray andperipheral white matters the white matter contains 3 types of nerve fibres Painful and thermal sensations ascend in thelateral spinothalamic tract 81. Summary contd Light (Crude) Touch and Pressure sensationascend through ant. Spinothalamic tract Discriminative Touch, Vibratory Sense, andConscious Muscle Joint Sense passes throughdorsal column The ventricles are four fluid-filled cavities locatedwithin the brain 82. Summary contd The cerebrospinal fluid is formed mainly in thechoroid plexuses of the lateral, third, and fourthventricles by active process CSF absorption is based on pressure gradient 83. References1. CLINICAL NEUROANATOMY ,BY SNELL, 7THEDITION2. CLINICAL NEUROANATOMY BY STEPHEN G.WAXMAN, 25TH EDTION3. NEUROANATOMICAL BASIS OF CLINICALNEUROLOGY,by Orhan Arslan4. MOORE, CLINICALLY ORIENTED ANATOMY,5TH EDITION5. GUYTON TEXTBOOK OF MEDICALPHYSIOLOGY, 11th edi 84. .Thank you