anatomy,physiology of spinal cord 7CSF
- 1. . Anatomy and physiology of spinal cord, ventricle and CSF kendeneh B.(R1) october 16, 2013
- 2. . Out line Anatomy of spinal cord Physiology of spinal cord Anatomy of ventricles Physiology of CSF
- 3. objectives To know basic anatomy of sp. Cord To understand the position of the main nerve pathways and nerve cell groups in the spinal cord To review basic structure of ventricle and to learn how CSF produced
- 4. Spinal cord It stretches from upper border of the foramen Magnum to the intervertebral disc between the first and second lumbar vertebrae. In the newborns, it extends to the level of the third lumbar vertebra Due to the differential growth of the vertebral column relative to the spinal cord, the spinal cord segments do not always correspond to the vertebral levels.
- 5. Accordingly, the cervical spinal nerves exit above their corresponding vertebrae the remaining spinal nerves emerge from the vertebral column below the corresponding vertebrae. When the dorsal and ventral roots of the lower lumbar and sacral segments assume a longer course around the conus medullaris to reach the corresponding intervertebral foramina, the cauda equina is formed
- 6. Spinal cord meniges is invested by the dura, arachnoid, and the pia mater. The dura mater is comprised of an inner meningeal and an outer endosteal layer. The outer endosteal layer forms the periosteum of the vertebral canal and the epineurium of the spinal nerves at or slightly beyond the intervertebral foramina.
- 7. . At the level of the second sacral vertebra the spinal dura joins the filum terminale to attach to the coccyx as the coccygeal ligament. The epidural space contains the internal vertebral plexus
- 8. . The arachnoid mater is a loose, irregular, and trabecular layer that is continuous with cranial arachnoid mater. surrounds the spinal cord without following the sulci. is pierced by vessels that supply the pia mater.
- 9. . The pia mater It intimately adheres to the spinal cord, giving rise to the dentate ligaments These ligaments are triangular extensions that extend to the dura, coursing between the dorsal and ventral roots. act as suspensory ligaments for the spinal cord
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- 11. Blood supply of spinal cord
- 12. Arteries of the Spinal Cord and Nerve Roots are branches of the vertebral, ascending cervical, deep cervical, intercostal, lumbar, and lateral sacral arteries Three longitudinal arteries supply the spinal cord: - an anterior spinal artery - paired posterior spinal arteries. The anterior spinal artery, formed by the union of branches of the vertebral arteries
- 13. Arteries of the Spinal Cord and Nerve Roots cont…d Sulcal arteries arise from the anterior spinal artery and enter the spinal cord through this fissure. Each posterior spinal artery is a branch of either the vertebral artery or the posteroinferior cerebellar artery. The posterior spinal arteries commonly form anastomosing channels in the pia mater.
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- 15. Arteries of the Spinal Cord and Nerve Roots cont…d The anterior and posterior segmental medullary arteries . The segmental medullary arteries are located chiefly where the need for a good blood supply to the spinal cord is greatest. 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 spinal veins . The veins draining the spinal cord join the internal vertebral (epidural) venous plexus in the epidural space . The internal vertebral venous plexus communicate with dural sinuses and vertebral veins in the cranium. The internal vertebral plexus also communicates with the external vertebral venous plexus on the external surface of the vertebrae.
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- 19. Internal organization Each spinal segment consists of central gray and peripheral white matters that are connected by the corresponding gray and white commissures. The central canal is a tube that pierces the gray commissure 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
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- 22. I. Nuclei of the posterior horn 1. Substatia gelatinosa situated at the apex of the posterior gray column throughout the length of the spinal cord receives afferent fibers concerned with pain, temperature, & touch impulses via central processes of dorsal root ganglion cells its axons cross to the opposite side in the white commissure & ascend in lat. white matter as the lat. spinothalamic tract
- 23. Nuclei of the posterior horn cont…d 2. Nucleus Proprius Situated in the middle part of the post horn anterior to the substantia gelatinosa throughout the spinal cord receives fibers from the posterior white column that are associated with the senses of position & movement, two-point discrimination, & vibration. its axons cross to the opposite side in the white commissure then ascend in the ant white matter as ant. spinothalamic tract
- 24. . 3. Clark’s/ dorsal nucleus situated at the base of the posterior gray column in the thoracic & upper lumbar region only The cells are associated with proprioceptive impulses Its axons ascend in the lat. column of the same side forming the posterior spinocerebellar tract
- 25. II. Nuclei of the anterior horn (motor) are grouped into 3 groups of motor nuclei 1. Medial group: ventromedial & dorsomedial nuclei - found in all segments of the spinal cord responsible for innervating the skeletal muscles of the neck & trunk.
- 26. . Nuclei of the anterior horn cont…d 2. Lateral group: ventrolateral & dorsolateral nuclei - present in the cervical & lumbosacral segments of the cord & responsible for innervating the skeletal muscles of the limbs 3. Central group: present in some cervical & lumbosacral segments phrenic nucleus (C3-C5 segments) – efferents supplying the diaphragm accessory nucleus (C1-C5/6 segments)
- 27. III. Nuclei of the lat. horn (autonomic) Formed by the intermediolateral group of cells 1) Sympathetic Present in the lat. horns of the segment from T1 to L2/3 its axons leave the cord through the ventral roots of the corresponding nerves as preganglionic fibers 2) Parasympathetic Present in the lat. horn of the S2,3,&4 spinal segments give rise to preganglionic parasympathetic fibers which 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 & the attachment 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 & the attachment of the ventral nerve roots. It contains descending tracts mainly.
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- 30. PATHWAYS IN WHITE MATTER the white matter contains 3 types of nerve fibres Ascending (sensory) tracts: carrying sensory impulses from the spinal cord to higher centers Descending or efferent tracts: carrying motor or autonomic impulses from higher centres to the spinal cord. Associative tracts: containing short ascending & descending fibres which coordinate the function of the different regions of spinal cord
- 31. Descending tracts Function maintenance of posture and balance, control of visceral and somatic reflex activity and muscle tone modification of the sensory signals
- 32. Descending Fiber Systems Upper Motor Neurons Are the nerve fibers that descend in the white matter from different supraspinal nerve centers provide numerous separate pathways that can influence motor activity. Lower Motor Neurons Are the motor neurons situated in the anterior gray columns of the spinal cord sending axons to innervate skeletal muscle constitute the final common pathway to the muscles.
- 33. , Descending pathway A. Corticospinal Tract Arises from the cerebral cortex Pathways is a large bundle of myelinated axons that descends through the brain stem via a tract called the medullary pyramid and then largely crosses over downward into the lateral white columns.
- 34. . The great majority of axons in the corticospinal system decussate in the pyramidal decussation within the medulla and descend within the lateral corticospinal tract These fibers terminate throughout the ventral gray column and at the base of the dorsal column.
- 36. . Function of cortico-spinal tract - concerned with voluntary, discrete, skilled movements, especially those of the distal parts of the limbs B. Rubrospinal tract: Arises from the red nucleus & crosses to the opposite side Descends in the lat. column of the spinal cord Function: relays impulses from the corpus striatum & cerebellum to the A.H.Cs of the spinal cord facilitates the activity of flexor muscles & inhibits the activity of extensor or antigravity muscles
- 38. . C. Tectospinal Tract: Arises from the sup. colliculus of midbrain Crosses to the opposite side Descends in the ant. column of the spinal cord Function concerned with reflex postural movements in response to visual stimuli
- 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 cord Function: facilitates the activity of the extensor muscles, inhibits the activity of the flexor muscles, & is concerned with the postural activity associated with balance.
- 42. Ascending tracts of the spinal cord Anatomical organization General information from the peripheral sensory endings is conducted through the nervous system by a series of neurons. The ascending pathway to consciousness consists of a three neuron chain: 1. The first-order neuron has its cell body in the posterior root ganglion of the spinal nerve. A peripheral process connects with a sensory receptor ending, whereas a central process enters the spinal cord through the posterior root to synapse on the second-order neuron.
- 43. . 2. The second-order neuron gives rise to an axon that decussates & ascends to a higher level of the central nervous system, where it synapses with the third-order neuron 3. The third-order neuron is usually in the thalamus & gives rise to a projection fiber that passes to a sensory region of the cerebral cortex
- 44. Simplest form of the ascending sensory pathway from the sensory nerve ending to the cerebral cortex
- 45. Ascending Pathways 1.Lateral Spinothalamic Tract The pain and thermal receptors in the skin and other tissues are free nerve endings. Painful and thermal sensations ascend in the lateral spinothalamic tract
- 46. Pain & temperature pathways
- 47. . 2.Anterior Spinothalamic Tract The axons enter the spinal cord from the posterior root ganglion and proceed to the tip of the posterior gray column where they divide into ascending and descending branches these fibers of the first-order neuron terminate by synapsing with cells in the substantia gelatinosa group in the posterior gray column Transmit impulses from light touch & pressure receptor
- 48. . Light/crud e touch & pressure pathways
- 49. . 3. posterior White Column: Fasciculus Gracilis and Fasciculus Cuneatus The axons enter the spinal cord from the posterior root ganglion and pass directly to the posterior white column of the same side. Here, the fibers divide into long ascending and short descending fiber these short descending fibers are involved with intersegmental reflexes For discriminative Touch, Vibratory Sense, and Conscious Muscle Joint Sense
- 50. .. Many of the long ascending fibers travel upward in the posterior white column as the fasciculus gracilis and fasciculus cuneatus. The fasciculus gracilis is present throughout the length of the spinal cord and contains the long ascending fibers from the sacral, lumbar, and lower six thoracic spinal nerves. The fasciculus cuneatus contains the long ascending fibers from the upper six thoracic and all the cervical spinal nerves.
- 51. . The fibers of the fasciculus gracilis and fasciculus cuneatus ascend ipsilaterally terminate by synapsing on the second-order neurons in the nuclei gracilis and cuneatus The axons of the second-order neurons decussate with the corresponding fibers of the opposite side in the sensory decussation. The fibers then ascend as a single compact bundle, the medial lemniscus, through the medulla oblongata, the pons, and the midbrain
- 52. . Many fibers in the fasciculus cuneatus from the cervical and upper thoracic segments, having terminated on the second-order neuron of the nucleus cuneatus, are relayed and travel as the axons of the second-order neurons to enter the cerebellum. The pathway is referred to as the cuneocerebellar tract
- 53. . 4. Posterior Spinocerebellar Tract The axons enter to the posterior gray column and terminate by synapsing on the second-order neurons at the base of the posterior gray column. The axons of the second-order neurons enter the posterolateral part of the lateral white column on the same side and ascend as the posterior spinocerebellar tract to the medulla oblongata. Here, the tract joins the inferior cerebellar peduncle and terminates in the cerebellar cortex to transmite muscle and Joint Sense impulse to the Cerebellum
- 54. . The posterior spinocerebellar fibers receive muscle joint information from the muscle spindles, tendon organs, and joint receptors of the trunk and lower limbs.
- 55. . 5.Anterior Spinocerebellar Tract The axons terminate by synapsing with the second-order neurons in the nucleus dorsalis at the base of the posterior gray column . The majority of the axons of the second-order neurons cross to the opposite side ascend as the anterior spinocerebellar tract in the contralateral white column; the minority of the axons ascend as the anterior spinocerebellar tract 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 ventricle 1. Lateral Ventricles There are two large lateral ventricles, and one is present in each cerebral hemisphere. may be divided into a body, which occupies the parietal lobe and from which anterior, posterior, and inferior horns extend.
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- 60. . -The body of the lateral ventricle extends from the interventricular foramen posteriorly as far as the posterior end of the thalamus. The body of the lateral ventricle has a roof, a floor, and a medial wall The roof - undersurface of the corpus callosum . The floor - the body of the caudate nucleus and the lateral margin of the thalamus The medial wall- septum pellucidum
- 61. . Choroid Plexus of the Lateral Ventricle projects into the ventricle on its medial aspect is a vascular fringe composed of pia mater covered with the ependymal lining of the ventricular cavity. The blood supply of the choroid plexuses is derived from the choroidal branches of the internal carotid and basilar arteries. The venous blood drains into the internal cerebral veins=> the great cerebral vein=> joins the inferior sagittal sinus to form the straight sinus.
- 62. . coronal section of the third and lateral ventricles at the site of the interventricular foramina showing the structure of the tela choroidea and its relationship with the ependyma and 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 ventricle Boundary The anterior - a thin sheet of gray matter, the lamina terminalis and ant. commissure
- 64. . The posterior wall is formed by the opening into the cerebral aqueduct. Superior to this opening is the small posterior commissure The lateral wall is formed by the medial surface of the thalamus superiorly and the hypothalamus inferiorly The superior wall is formed by a layer of ependyma that is continuous with the lining of the ventricle
- 65. . The inferior wall is formed by the optic chiasma, the tuber cinereum, the infundibulum and the mammillary bodies
- 66. Sagittal section of the brain showing the medial surface of the diencephalon
- 67. . 3. Fourth Ventricle is a tent-shaped cavity filled with cerebrospinal fluid. is situated anterior to the cerebellum and posterior to the pons and the superior half of the medulla oblongata. 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 cerebellar peduncle and the cranial part by the superior cerebellar peduncle. Posterior Wall The tent-shaped roof projects into the cerebellum. The superior part is by the medial borders of the two superior cerebellar peduncles and the superior medullary velum
- 69. . The inferior part of the roof is formed by the inferior medullary velum Floor is formed by the posterior surface of the pons and the cranial half of the medulla oblongata
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- 71. Cerebrospinal Fluid The cerebrospinal fluid is found in the ventricles of the brain and in the subarachnoid space around the brain and spinal cord
- 72. The Physical Characteristics and Composition of the Cerebrospinal Fluid
- 73. . Functions of CSF serves as a cushion between the central nervous system and the surrounding bones, thus protecting it against mechanical trauma. it provides mechanical buoyancy and support for the brain. assist in the regulation of the contents of the skull.
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- 75. . Formation of CSF The cerebrospinal fluid is formed mainly in the choroid plexuses of the lateral, third, and fourth ventricles production of cerebrospinal fluid is not pressure regulated
- 76. . Circulation of CSF The circulation begins with its secretion from the choroid plexuses in the ventricles. aided by the arterial pulsations of the choroid plexuses and by the cilia on the ependymal cells lining the ventricles.
- 77. . Absorption of CSF The main sites are the arachnoid villi that project into the dural venous sinuses The arachnoid villi tend to be grouped together to form elevations known as arachnoid granulations. Structurally, each arachnoid villus is a diverticulum of the subarachnoid space
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- 79. summary SP. cord stretches from upper border of the foramen Magnum to the intervertebral disc between the first and second lumbar vertebrae and occupy 2/3 of upper vertebra is invested by the dura, arachnoid, and the pia mater Both pia and arachnoid mater form the leptomeninges, and they continue around the spinal nerves as perineurium
- 80. Summary cont…d Three longitudinal arteries supply the spinal cord The veins draining the spinal cord join the internal vertebral venous plexus in the epidural space Each spinal segment consists of central gray and peripheral white matters the white matter contains 3 types of nerve fibres Painful and thermal sensations ascend in the lateral spinothalamic tract
- 81. Summary cont…d Light (Crude) Touch and Pressure sensation ascend through ant. Spinothalamic tract Discriminative Touch, Vibratory Sense, and Conscious Muscle Joint Sense passes through dorsal column The ventricles are four fluid-filled cavities located within the brain
- 82. Summary cont…d The cerebrospinal fluid is formed mainly in the choroid plexuses of the lateral, third, and fourth ventricles by active process CSF absorption is based on pressure gradient
- 83. References 1. CLINICAL NEUROANATOMY ,BY SNELL, 7TH EDITION 2. CLINICAL NEUROANATOMY BY STEPHEN G. WAXMAN, 25TH EDTION 3. NEUROANATOMICAL BASIS OF CLINICAL NEUROLOGY,by Orhan Arslan 4. MOORE, CLINICALLY ORIENTED ANATOMY, 5TH EDITION 5. GUYTON TEXTBOOK OF MEDICAL PHYSIOLOGY, 11th edi
- 84. . Thank you