Spinal Cord - Internal Structures PDF

Spinal Cord-- Internal structures Gray matter 灰质 Inside of spinal cord Central canal 中央管 At the center of the gray matter White matter 白质 In the periphery White matter...

Spinal Cord-- Internal structures Gray matter 灰质 Inside of spinal cord Central canal 中央管 At the center of the gray matter White matter 白质 In the periphery White matter Central canal Gray matter Transverse section of the adult spinal cord  Spinal Cord-- Internal structures White Gray matter 灰质 matter 1.Relatively dull color during fresh condition. 2.Contains the cell body, dendrites, and Centra proximal parts of the axons of neurons. l canal Gray matter 3.“H” or “butterfly” –shaped in cross sections. 4.A narrow transverse connection joining the two portions is the gray commissure. White matter Central canal 中央管 Gray matter Is a tube filled with CSF and opens upward into the inferior portion of the fourth ventricle. Thoracic segment White matter White matter 白质 1.Bright, pearly white during fresh condition. 2. Is composed of bundles of axons, called tracts, Gray matter that carry signals from one part of the CNS to another. Gray commissure Lumber segment  Spinal Cord-- Internal structures Gray matter （each half）灰质 Posterior horn (column) 后角(柱) Anterior horn (column)前角（柱） Intermediate zone 中间带 ----Lateral horn 侧角 (T1 – L2 or L3) on each side of intermediate zone near the base of the anterior horn. P L A  Spinal Cord-- Internal structures White matter 白质 Consists of bundles of axons that ② course up and down the cord. Has Gray matter three pairs of columns, or funiculi ③ ①Anterior funiculus 前索 ④ ① ②Posterior funiculus 后索 spinal cord ③Lateral funiculus 外侧索 anterolateral ④Anterior white commissure sulcus anterolateral sulcus 白质前连合 anterior median fissure Anterior Funiculus Posterior funiculus Lateral funiculus  Spinal Cord-- Internal structures The shape and size of the gray matter varies according to spinal cord level. At the lower levels, the ratio between gray matter and white matter is greater than in higher levels, mainly because lower levels contain less ascending and descending nerve fibers.  Spinal Cord-- Internal structures Gray matter 灰质 Posterior horn Comprised of sensory nuclei that receive and process incoming somatosensory information. The prominent nuclear groups of cell columns from dorsal to ventral respectively are ♦ Posteromarginal nucleus （后角边缘核） ♦ Substantia gelatinosa （ 胶状质） ♦ Nucleus proprius （后角固有核） ♦ Thoracic nucleus (胸核） or Dorsal nucleus ( Clarke column)  Spinal Cord-- Internal structures Posterior horn Gray matter 灰质 The posteromarginal nucleus Lies in the tip of the dorsal horn and is found at all spinal cord levels. It receives some of incoming dorsal root Posteromarginal nucleus fibers of spinal nerves, The axons of its neurons Substantia gelatinosa contribute to the contralateral spinothalamic tract which relays pain and temperature Nucleus proprius information to the thalamus. thoracic nucleus Substantia gelatinosa Lies anterior to posteromarginal nucleus and Intermediolateral is found at all spinal cord levels. nucleus It is made up of Golgi type Ⅱ neurons, it Lateral motor neurons relays pain, temperature and mechanical Medial motor neurons (light touch) information, receives dorsal root fibers of spinal nerves, and synapses on dendrites in Nucleus proprius, whose axons contribute to the contralateral spinothalamic tract.  Spinal Cord-- Internal structures Posterior horn Gray matter 灰质 Nucleus proprius (proper sensory nucleus) Posteromarginal nucleus Located below the substantia gelatinosa in neck Substantia gelatinosa of the dorsal horn of all spinal cord levels. Receives many sensory (associated with Nucleus proprius mechanical and temperature sensations) inputs. Thoracic nucleus Contributes to contralateral ventral and lateral spinothalamic tracts to the thalamus. Intermediolateral Thoracic nucleus (or Dorsal nucleus of Clarke ) nucleus Located only in the mid-portion of the base of Lateral motor neurons the dorsal horn in segments T1-L3 of the spinal Medial motor neurons cord Receives the information of unconscious proprioception from muscle spindles and Golgi tendon organs. Projects ipsilaterally to the lateral funiculus and form the dorsal spinocerebellar tract, sends unconscious proprioception to the cerebellum.  Spinal Cord-- Internal structures Gray matter 灰质 Intermediate zone ♦ Intermediolateral nucleus (中间外侧核） (Lateral horn or column) Lies only in segments T1-L3 of spinal cord, contains sympathetic preganglionic neurons. Their axons enter into the ventral spinal roots. ♦ Sacral parasympathetic nucleus（骶副交感核） Lies only in segments S2-S4, contains parasympathetic preganglionic neurons. ♦ Intermediomedial nucleus（中间内侧核） Lies lateral to lamina X at all cord levels. Receives primary visceral afferents Projects to the intermediolateral nucleus and may be involved in visceral reflexed.  Spinal Cord-- Internal structures Gray matter 灰质 Anterior horn (contains motor neurons) Contains motor nuclei consisting of α, γ-motor neurons and Renshaw’s cell. Be found at all levels of the spinal cord. They are the final common pathway of the motor system. They innervate the skeletal muscles. ☻ Three kinds of neuron ♦ α-motor neurons: larger multipolar neuron, innervate extrafusal fibers of skeletal muscle, producing contraction of muscle. afferent neuron ♦ γ-motor neurons: smaller neuron, innervate intrafusal fibers regulating muscular tonus. Renshaw’s cell ♦ Renshaw’s cell: relating to negative feedback mechanism. α-motor neuron  Spinal Cord-- Internal structures Gray matter 灰质 Anterior horn (contain motor neurons) ☻ Two groups of nuclei ♦ Medial motor neuron: present in most segments of spinal cord, innervating axial muscles. ♦ Lateral motor neuron: present only in cervical and lumbosacral enlargements, innervating limb m. Lateral Medial Lateral  Spinal Cord-- Internal structures Gray matter 灰质 Rexed’S Lamina(莱克斯德板层) Based on cytoarchitectural features, a cross section of the gray matter of the spinal cord is classified into ten laminae (I–X) by Rexed. Posterior horn composed of laminae Ⅰ–Ⅵ Intermediate zone composed of lamina Ⅶ Anterior horn composed of laminae Ⅷ and Ⅸ Lamina Ⅹ is the gray matter surrounding the central canal.  Spinal Cord-- Internal structures Gray matter 灰质 General correlation of laminae with some of the major nuclei: Ⅰ：corresponds to posteromarginal nucleus. Ⅱ： substantia gelatinosa. Ⅲ and Ⅳ： nucleus proprius. Ⅴ and Ⅵ：interneurons, lies in neck and base of the dorsal horn, sometimes described as containing the spinal reticular formation. Ⅶ： Clarke nucleus (thoracic nucleus), intermediomedial nucleus, intermediolateral nucleus. Ⅷ： commissural nuclei, interneurons. Ⅸ： motor nuclei of ventral horn.  Spinal Cord-- Internal structures Gray matter 灰质 General correlation of laminae with some of the major nuclei:  Spinal Cord-- Internal structures Gray matter 灰质 General correlation of laminae with some of the major nuclei:  Spinal Cord-- Internal structures Gray matter 灰质 Relationship between the gray matter and the spinal nerve: 1) posterior horn links with both somatic and visceral sensory fibers; 2) anterior horn links with somatic motor fibers; 3) lateral horn links with sympathetic (visceral motor) fibers  Spinal Cord-- Internal structures White matter 白质 surrounding the gray matter and containing nerve fibers. These fibers conduct information up or down the cord. All fibers in the cord have 5 types: 1) afferent fibers 2) efferent fibers 3) intersegmental fibers 4) long ascending fibers: conducting afferent impulses to supraspinal levels 5) long descending fibers: from supraspinal sources to synapse with spinal neurons Fibers of the type 4 and 5 form longitudinal bundles with more or less distinct demarcation  Spinal Cord-- White matter 白质 Organization of the dorsal root and its relationship with the main ascending tracts: 1)lateral division: are thin fibers, convey impulses related to pain, thermal and light touch sense, pain and thermal fibers enter contralateral lateral spinothalamic tract, light touch fibers enter contralateral anterior spinothalamic tract; 2)medial division: are thick fibers and convey sensation of fine touch, movement and proprioception, which enter posterior funiculus to form gracile and cuneate fasciculi.  Spinal Cord-- White matter 白质 Long ascending tracts: transmit sensory information from the sensory receptors to higher levels of the CNS. FG Fasciculus gracilis; FC Fasciculus cuneatus; STT spinothalamic tracts; DSCT and VSCT Dorsal spinocerebellar tract and Ventral spinocerebellar tract Long descending tracts: carry information associated with maintenance of motor activities CST Corticospinal tract--lateral corticospinal tract and anterior corticospinal tract; RST Rubrospinal tract; RT+VST Reticulospinal tract + Vestibulospinal tract; TST Tectospinal tract FC FG SCT D CST RST VS RT RT CT ST CSTa T TST VST  Spinal Cord-- White matter 白质 ☻ Ascending tracts Postcentral gyrus Fasciculus gracilis FG 薄束 Dorsal column system Internal capsule Fasciculus cuneatus FC 楔束 Position: within the posterior funiculus; arising from the thick and large ipsilateral Medial lemniscus fibers of the medial part of dorsal root and ending in the gracile and cuneate nuclei in Gracile and the medulla. cuneate nuclei Function: convey sensation of fine touch, Decussation of medial lemniscus vibration, two-point discrimination, conscious FG or FC proprioception and position sense. Thoracic 4 is Spinal the demarcation for FG and FC ganglionic FC FG cell CST RST RT Fasciculus gracilis and cuneatus VST  Spinal Cord-- White matter 白质 FC ☻ Ascending tracts FG FC Fasciculus gracilis FG 薄束 Dorsal column system Fasciculus cuneatus FC 楔束 Position: within the posterior funiculus; arising from the thick and large ipsilateral FG fibers of the medial part of dorsal root and ending in the gracile and cuneate nuclei in the medulla. Function: convey sensation of fine touch, vibration, two-point discrimination, conscious proprioception and position sense. Thoracic 4 is the demarcation for FG and FC Fasciculus gracilis and cuneatus FC FG CST RST RT VST  Spinal Cord-- White matter 白质 ☻ Ascending tracts Fasciculus gracilis FG 薄束 Fasciculus cuneatus FC 楔束 Somatotopic organization: Fibers are arranged in an orderly fashion from medial to lateral in relation to the regions of the body from down up. The fibers from lower segments are more medial than the higher ones. Fasciculus cuneatus deal with sensations from the upper limb C Th L S Fasciculus gracilis FC FG T L C h deal with S sensations from the lower limb  Spinal Cord-- White matter 白质 ☻ Ascending tracts Spinothalamic tract STT 脊髓丘脑束 Position: anterior STT in the anterior funiculus, lateral STT in the lateral funiculus. Function: 1) anterior STT conveys impulses of light touch and pressure sensations ; 2) lateral STT conducts pain and temperature sensibilities Some anatomical details: 1) all the fibers come from the lateral part of the dorsal root. 2) all primary fibers relay in laminae Ⅰ and Ⅳ-Ⅷ. 3) majority of fibers cross the median line in anterior white Neurons of commissure to contralateral dorsal horn tract. Anterior SCT 4) decussation is completed Lateral STT in the segment above the STT entrance of the dorsal root. STT Anterior STT Anterior white commissure  Spinal Cord-- White matter 白质 Postcentral ☻ Ascending tracts gyrus Internal Spinothalamic tract STT 脊髓丘脑束 capsule Position: anterior STT in the anterior funiculus, lateral STT in the lateral funiculus. Thalamus Function: 1) anterior STT conveys impulses of light touch and pressure sensations ; 2) lateral STT conducts pain and temperature sensibilities Some anatomical details: 1) all the fibers Spinothalamic tract come from the lateral part of the dorsal root. 2) all primary fibers relay in laminae Ⅰ and Ⅳ-Ⅷ. 3) majority of fibers cross the median line in anterior white Nucleus proprius commissure to contralateral Dorsolateral tract tract. 4) decussation is completed Spinal ganglionic in the segment above the cell entrance of the dorsal root. Spinothalamic tract  Spinal Cord-- White matter 白质 ☻ Ascending tracts Spinothalamic tract STT 脊髓丘脑束 Somatotopic organization: Fibers are arranged from lateral Sensations temperature to medial in relation to the regions of pain light touch the body from down up. pressure Anterior white Neurons of commissure dorsal horn Lateral STT Anterior STT S L Th C Nerve fibers Lateral STT Anterior STT Neurnes of Spinal Ganglia dorsal horn  Spinal Cord-- White matter 白质 ☻ Ascending tracts Superior peduncle Spinocerebellar tract SCT 脊髓小脑束 Lying in margine of the lateral funiculus Two parts---anterior SCT / posterior SCT Anterior spinocerebellar tract ：Originate from Pons contralateral lamina Ⅴ~Ⅶ of lumber enlargment, cross to the other side and ascend into cerebellum Medulla oblongata via superior peduncle. Inferior Function: transmits unconscious proprioceptive cerebellar impulse from lower limb and lower portion of trunk. peduncle Thoracic nucleus Anterior Lamina Ⅴ~Ⅶ spinocerebellar tract Posterior SCT Spinal Cord Posterior Anterior SCT spinocerebellar tract  Spinal Cord-- White matter 白质 ☻ Ascending tracts Superior peduncle Spinocerebellar tract SCT 脊髓小脑束 Two parts, lying in margin of the lateral funiculus Posterior spinocerebellar tract ：Originates from ipsilateral thoracic nucleus and ascends into Pons cerebellum via inferior peduncle without decussation. Function: transmits unconscious proprioceptive Medulla oblongata impulse from lower limb and lower portion of trunk. Inferior cerebellar peduncle Thoracic nucleus Anterior Lamina Ⅴ~Ⅶ spinocerebellar tract Posterior SCT Spinal Cord Posterior Anterior SCT spinocerebellar tract  Spinal Cord-- White matter 白质 ☻ Ascending tracts Tract Site of origin Funiculus Termination Function Spinal ganglia Convey conscious Fasciculus Gracile below segment proprioceptive, gracilis nucleus T5 vibration, position Posterior sense and fine Spinal ganglia discriminative touch Fasciculus Cuneate above segment sensation of trunk and cuneatus nucleus T4 limbs Posterior ipsilateral spinocerebellar thoracic nucleus Unconscious proprioception from Lateral cerebellum Anterior lower limb and lower Contralateral portion of trunk spinocerebellar LaminaeⅤ~Ⅶ Lateral and Pain, temperature and LaminaeⅠ,Ⅳ~ Dorsal Spinothalamic anterior light touch sensation of Ⅶ thalamus trunk and limbs  Spinal Cord-- White matter 白质 ☻ Descending tracts To originate from different cortical areas and from brain stem nuclei. The descending pathways carry information associated with maintenance of motor activities such as posture, balance, muscle tone, and visceral and somatic reflex activity. lo ng CST de RST sc en di RT+VST ng tra ct s TST  Spinal Cord-- White matter 白质 ☻ Descending tracts 1. Corticospinal tract CST 皮质脊髓束 the most mportant descending projection pathway for controlling voluntary movements. precentral motor cortex Arise from: premotor area pass through internal capsule decussation of brain stem pyramids Pyramidal decussation Lateral CST Anterior CST Crossed fibers Uncrossed fibers Lateral CST Anterior CST Schema of pyramidal decussation  Spinal Cord-- White matter 白质 ☻ Descending tracts 1. Corticospinal tract CST 皮质脊髓束 Lateral CST: Position: the lateral funiculus, medial to posterior spinocerebellar tract Ending: The motor nuclei in ipsilateral anterior horn of the cervical and lumbosacral enlargements. Function: Contral ipsilateral distal limb muscles Lateral CST Anterior CST Somatotopic Fibers are arranged from lateral to medial in organization: relation to the regions of the body from down up. Fibers controlling the lowest part of the body are most laterally placed Schema of pyramidal decussation Anterior CST: Position: the anterior funiculus, both sides of the anterior S median fissure, extends only to the upper thoracic cord. L T C Ending: The axial and girdle motor nuclei in bilateral anterior horn. Lateral CST Function: contral bilateral neck, shoulder,and upper trunk muscles Anterior CST  Spinal Cord-- White matter 白质 ☻ Descending tracts 2.Rubrospinal tract (RST红核脊髓束) c Position anterior to the lateral corticospinal tract Originates from the red nucleus in the midbrain and crosses to the opposite, then descends to spinal cord. Ends laminae V - VII of the cervical cord. Function: controls limb muscles and Red nucleus regulating voluntary movement, excites flexor muscles and inhibits extensor ones Rubrospinal Midbrain tract Reticular FG Medulla formation SCT FC oblongata D CST RST Reticulospinal tract VS ST Spinal cord Anterior horn CT T Minor descending tracts  Spinal Cord-- White matter 白质 ☻ Descending tracts 3.Vestibulospinal tract (VST前庭脊髓束) Position: anterolateral funiculus of all spinal cord Arises from the lateral vestibular nucleus， which receives impulses for balance from the inner ear. and descends ipsilaterally. Ends all levels of laminae VII – VIII.. Function: Excites motor neurons of extensor muscles and inhibits those of flexor muscles Vestibulospinal FG tract SCT FC D CST VS ST CT T VST  Spinal Cord-- White matter 白质 ☻ Descending tracts 4.Reticulospinal tract （RT网状脊髓束） Position: ventral and lateral funiculus of all spinal cord Arises from the nucleus of the pons and medullary reticular formation and descends ipsilaterally. Ends laminae VII – VIII. Function: controls muscles of the upper and lower limbs, especially to maintain Reticulospinal posture and balance. tract FG SCT FC D CST VS ST CT T Reticulospinal tract  Spinal Cord-- White matter 白质 ☻ Descending tracts 5.Tectospinal tract （TST顶盖脊髓束） Position： medial part of the anterior funiculus of the upper cervical spinal cord Arises from the midbrain and crosses to the contralateral side, through the brainstem to the upper spinal cord Ending laminae VI-VII of upper cervical cord segments. Function: innervates muscles of the neck; Tectospinal coordinates head movements with eye movements. tract maybe cause turning in response to sudden sights and sounds. FC FG SCT D CST RST VS ST CT T Tectospinal tract  ☻ Main descending tracts Tract Site of origin Funiculus Termination Function Lateral Cerebral cortex Lateral corticospinal Laminae IV - IX Voluntary movement Anterior Anterior horn Cerebral cortex Anterior corticospinal Laminae Rubrospinal Red nucleus Lateral V - VII Excitatory of flexors or Homolateral Laminae extensors Vestibulo-spinal vestibular nuclei Anterior VII - VIII Vestibular Anterior and Laminae Reticulospinal Voluntary movement nuclei lateral VII - VIII Medial Superior Laminae longitudinal anterior colliculus VII - VIII Coordinate neck with fasciculus eye movement Superior Laminae Tectospinal Anterior colliculus VI-VII Fasciculus Anterior, lateral Intrinsic reflex mechanism Spinal cord Spinal cord of spinal cord proprius and posterior  Spinal Cord-- White matter 白质 Four long pathways FG Fasciculus gracilis; FC Fasciculus cuneatus; STT spinothalamic tracts； CST Corticospinal tract lBrown-Séquard’s syndrome.脊髓半横断综 合征 Hemisection of the spinal cord often due to a bullet or knife wound，the main signs and symptoms include: — contralateral loss of pain and temperature below the level of the lesion; --- ipsilateral loss of conscious proprioception below the level of the lesion; — ipsilateral spastic paralysis of muscles below the level of the lesion. conscious proprioceptive, vibration, position Pain,temperature  Spinal Cord-- White matter 白质 Four long pathways FG Fasciculus gracilis; FC Fasciculus cuneatus; STT spinothalamic tracts； CST Corticospinal tract lBrown-Séquard’s syndrome.脊髓半横断综 合征 Hemisection of the spinal cord often due to a bullet or knife wound，the main signs and symptoms include: — contralateral loss of pain and temperature C Th L S CST below the level of the lesion; --- ipsilateral loss of conscious T L C h proprioception below the level of the lesion; S — ipsilateral spastic paralysis of muscles STT below the level of the lesion.  Functions of Spinal Cord ① Conductivity Functions of Spinal Cord ② Reflexes ① Conductivity Convey afferent impulses from the somatic and visceral receptors to the brain Spinothalamic tracts Conduct efferent impulses Fasciculus gracilis from the brain to the effectors Fasciculus cuneatus Corticospinal tract  Functions of Spinal Cord ② Reflexes are involuntary responses to stimuli A. Stretch reflex (such as Knee-jerk reflex) Innervated skeletal muscle, when stretched by an external force, can reflexively cause the muscle to contract, which is called the stretch reflex. Afferent neuron B. γ- reflex loop Internuncial neuron C. Flexor reflex Alpha motor neuron When the skin in one part of the Cutaneous body is injured, the phenomenon of ending buckling reaction occurs in the Motor end-plates body. Schematic diagram of a flexor reflex arc  Highlights of this chapter Important Concepts Grey matter ( Cortex ) White matter (medulla ) Nucleus Nerve tract Ganglion Conus medullaris Subarachnoid space Segment of spinal cord Anterior white commissure Important Contents 1. The subdivisions of nervous system; Classification of neurons; 2. The Position and external features of Spinal Cord; 3. The subdivisions of Gray matter of spinal cord and nuclei in each part; 4. General correlation of Rexed’S laminae with some of the major nuclei; 5. The position，function and somatotopic organization of Fasciculus gracilis(FG)， Fasciculus cuneatus (FC)，Spinothalamic tracts (STT) and Corticospinal tract (CST); 6. Functions of Spinal Cord.  Specimen of the spinal cord 1. On the cross sections of the brain and spinal cord, you will observe Grey matter ( Cortex ), White matter (medulla ), Nucleus; Arounding the spinal cord, you will observe Ganglion , Nerve 2.The Position and external features of Spinal Cord Conus medullaris, two Enlargements, Filum terminale, Cauda equina, anterior median fissure, posterior median sulcus, anterolateral sulcus and Posterolateral sulcus. dura mater, arachnoid mater 3. Internal features of Spinal Cord Anterior funiculus, Posterior funiculus, Lateral funiculus of the white matter; Anterior horn, Posterior horn, Intermediate zone and Lateral horn of gray matter