Neuroanatomy Internal structure of 1 Spinal Cord Capt. Piyachat Chansela Department of Anatomy Academic year 201603/05/60
Outline & Objectives KNOW AND UNDERSTAND; 2 Gray and white matter at each spinal level Distribution of spinal neurons Blood supply of spinal cord Functional component CLINICAL PANELS; Lower limb withdrawal reflex Muscle Stretch Reflex03/05/60
Midbrain Pons Upper medulla Lower medulla C-spine T-spine03/05/60 L-spine 3 what-when-how In Depth Tutorials and Information
The spinal cord participates in four essential functions1. It receives 1.1 somatosensory fibers: sensory input from receptors in skin, skeletal muscles, and tendons 1.2 viscerosensory fibers: sensory input from receptors in thoracic, abdominal, and pelvic viscera2. It contains 2.1 somatic motor neurons: that innervate skeletal muscles 2.2 visceral motor neurons: influence smooth and cardiac muscle and glandular epithelium3. Spinal reflex somatosensory fibers enter the spinal cord and influence anterior horn motor neurons. These activated motor neurons, in turn, produce rapid involuntary contractions of skeletal muscles.4. The spinal cord contains descending fibers that influence the activity of spinal neurons. These fibers originate in the cerebral cortex and brainstem, and damage to them may give rise to decorticate rigidity or an alternating hemianesthesia.03/05/60 4
03/05/60 Cervical Enlargement (C4-T1) LS Enlargement (T11-S1) 5
The arrangement of gray and white matter The cervical and lumbosacral enlargements are produced by expansions of the gray matter. White matter is most abundant in the upper reaches of the cord. In the posterior funiculus, e.g., The gracile fasciculus carries information from the lower limb and is present at all segmental levels, whereas The cuneate fasciculus carries information from the upper limb and is not seen at lumbar level.03/05/60 6
The gray matter is divided into a posterior (dorsal) horn, an anterior(ventral) horn. On the basis of the shape, size, and distribution of neurons locatedin these areas, the gray matter is divided into laminae (Rexed laminae). Dorsal median septum Dorsal intermediate sulcus Dorsal funiculus Dorsal horn Central canal Lateral funiculus Intermediate zone Anterior white commissure Ventral horn Ventral funiculus03/05/60 Ventral median fissure 7
The gray matter : Anterior (ventral) horn Flexors Extensors03/05/60 8
The somatomotor cell columns Ventromedial (all segments) Erector spinae Dorsomedial (T1–L2) Intercostals, abdominals A E Ventrolateral (C5–C8, L2–S2) Arm/thigh B F D Dorsolateral (C6–C8, L3–S3) Forearm/leg C Retrodorsolateral (C8, T1, S1–S2) Hand/foot Central (C3–C5) Diaphragm Flexors Intermediolateral Central Anterolateral Posterolateral Retroposterolateral F E A D B C Posteromedial03/05/60 Extensors Anteromedial 9 http://clinicalgate.com/spinal-cord-2/
The gray matter : Posterior (dorsal) horn PM: Posteromarginal nucleus SG: Substantia gelatinosa NP: Nucleus proprius ND: Nucleus dorsalis (of Clarke)03/05/60 SVG: Secondary visceral gray 10 IML: Intermediolateral cell column
03/05/60 http://clinicalgate.com/the-somatosensory-system-ii-nociception-thermal-sense-and-1t1ouch/
Cytoarchitectural laminae (The Rexed Laminae) Lamina I The outer most thin layer consist of large Receive pain and temperature neurons (posteromarginal nucleus) afferents from Lissauer’s tractD Contralateral spinothalamic tract Lamina II Contain interneurons : substantia gelatinosaOR Lamina III and IV Thick layer contains : nucleus proprius VI receive many descending andS Laminae V and VI Reticular nucleus, SVG ascending fibers etc., the corticospinalA tract, withdrawal reflexL • Medial portion between C8 and L3 • Posterior spinocerebellar tract Lamina VII Nucleus dorsalis (of Clarke), • Preganglionic sympathetic • Lateral portion between T1-L2, S2-4 neurons between T1 and L2, and Intermediolateral cell column preganglionic parasympathetic neurons between S2 and S4V Lamina VIII Interneurons involved in motor control • medial nuclear group axial and proximal musclesE Somatic motor neurons, large multipolar neurons • lateral nuclear groupN Lamina IX (cervical and lumbar enlargements)T Surrounds the central canal (small neurons) innervates distal extremity musclesR Receive dorsal root afferents involvedA Lamina X with pain, temperature, and visceralL 03/05/60 sensation 12
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The medial stream comprises medium and large fibers which divide White Matterwithin the posterior funiculus into ascending and descendingbranches. The branches swing into the posterior gray horn andsynapse in laminae II, III, and IV. The largest ascending fibers run allthe way to the posterior column nuclei (gracilis/cuneatus) in themedulla oblongata. “Dorsal column system” The lateral stream comprises small (Aδ and C) fibers which, upon entry, divide into short ascending and descending branches within the posterolateral tract of Lissauer. They synapse upon neurons in the marginal zone (lamina I) and in the substantia gelatinosa (lamina II); some fibers synapse upon dendrites of cells belonging to laminae III–V.03/05/60 14
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White Matter 1. The posterior funiculus 2. The lateral funiculus 03/05/60 3. The anterior funiculus Posterior funiculus Lateral funiculus Anterior funiculus 16
posterior funiculus 1. The posterior funiculus consists of the gracile and cuneateLateral funiculus fasciculi; dorsal (posterior) columns system 2. The lateral funiculus contains the - lateral corticospinal tract ALS - anterolateral system (ALS) - spinocerebellar tract 3. The anterior funiculus contains - reticulospinal - vestibulospinal fibers 03/05/60 - anterior corticospinal tract - medial longitudinal fasciculus (MLF) Anterior funiculus 17
FUNICULUS TRACTS AND FIBERS ORIGIN TERMINATION Gracile fasciculus (↑) Posterior root ganglia ↓ T6 Medulla (gracile Cuneate fasciculus (↑) nucleus) Postsynaptic posterior Medulla (cuneatePosterior column system (↑) Posterior root ganglia ↑ T6 nucleus)Anterior Anterior corticospinal (↓) Medial reticulospinal (↓) Lamina IV (III-VII) Medulla MLF (↓) Medial vestibulospinal Cerebral cortex Laminae VI-IX Pontine reticular nucleus Laminae VIII (VII, IX) Reticulospinal (oralis, caudalis) Tectospinal Medial vestibular nucleus Laminae VII-VIII Medullary reticular Laminae VI-VIII formation Tectum (midbrain) Laminae VI-VIII03/05/60 18
FUNICULUS TRACTS AND FIBERS ORIGIN TERMINATION Lateral corticospinal (↓) Cerebral cortex Laminae IV-IX Posterior spinocerebellar (↑) Clarke nucleus (lamina VII) Cerebellum Anterior spinocerebellar (↑) Laminae VII-IX Cerebellum Spinothalamic ThalamusLateral Spinomesencephalic Midbrain Spinoreticular Reticular formation Rubrospinal (↓) Red nucleus Laminae V-VIII Lateral reticulospinal (↓) Lateral vestibulospinal (↓) Gigantocellular reticular Laminae VII (VI-IX) nucleus Lateral vestibular nucleus Laminae VII-VIII Cuneocerebellar (↑) Lateral cuneate nucleus Cerebellum03/05/60 19
Posterior spinal a. The three spinal arteries; (1) Posterior spinal a. Arterial (2) Anterior spinal a.vasocorona (3) Radiculospinal a. from the vertebral arteries and from intercostal arteries. Posterior spinal a. Radiculospinal a. Anterior spinal a. (ASA) Anterior spinal a20.* Terminal branches of the spinal medullary a. 03/05/60join to form, the arterial vasocorona
Functional component of spinal cord SSA GSA SVA GVA GVE SVE GSE03/05/60 21
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Lower limb withdrawal reflex Sequence of events (1a) Plantar nociceptors send impulse trains along tibial–sciatic afferent fibers. (1b) Ascend cauda equina and enter L5. (1c) Some impulses are despatched up and down Lissauer’s tract 1-2 segments. (2a) Excite flexor reflex internuncials and target motor neurons. (2b) Axons of medially placed internuncials cross the midline to activate contralateral internuncials. (3) On the stimulated side, α and γ motor neurons contract iliopsoas (a), hamstrings (b), & ankle dorsiflexors (d). (4) On the contralateral side, α and γ motor neurons contract gluteus maximus and03/05/60 quadriceps femoris (c). 26
Muscle Stretch Reflex Sometimes called a tendon reflex or deep tendon reflex, commonly examine on knee jerk called quadriceps stretch reflex. PE: tap on the patellar tendon stretches the primary sensory endings in muscle spindles The central processes of these afferent axons synapse on and excite motor neurons in the anterior horn that innervate the quadriceps femoris muscle. The result is a sudden contraction of these muscles and extension (dorsiflexion) of the leg at the knee.03/05/60 27
Neuroanatomy Spinal Cord 28 Ascending pathway Capt. Piyachat Chansela Department of Anatomy Academic year 201603/05/60
Outline & Objectives KNOW AND UNDERSTAND; 29 Conscious sensation 1) the posterior column–medial lemniscal pathway and; 2) the spinothalamic (anterolateral) pathway. Nonconscious sensation The spinocerebellar pathways Refer pain Other Ascending Pathways CLINICAL PANELS; Sensory ataxia03/05/60
RECEPTOR TYPE SENSATION RECEPTOR TYPE SENSATIONGolgi tendon organ Proprioception Meissner corpuscle Tap, flutterMuscle spindle Proprioception Hair follicle receptors Motion, direction Pacinian corpuscle Vibration Merkel cell Touch—pressure Ruffini corpuscle Skin stretch03/05/60 30
Afferent fibers of posterior nerve root before enter posteriorfuniculus are divided into 2 divisions.1) lateral division 2) medial division Pain temp Conscious Fine touch Nonconscious03/05/60 31
1) lateral division 2) medial division Pain temp Conscious Lateral root entry Fine touch C-fiberDRG Nonconscious Dorsal column Medial root entry A DRG A03/05/60 A 32
Conscious sensations Conscious proprioceptive sensations arise within the body. The receptors concerned are those of the locomotor system (muscles, joints, bones). The pathways to the cerebral cortex form the substrate for position sense when the body is stationary, and for kinesthetic sense during movement. Two major pathways are involved in somatic sensory perception. 1) the posterior column–medial lemniscal pathway and; 2) the spinothalamic (anterolateral) pathway.Nonconscious sensations These also are of two kinds. Nonconscious proprioception is the term used to describe afferent information reaching the cerebellum through the spinocerebellar pathways. This information is essential for smooth motor coordination. Second, interoception is a little-used term referring to unconscious afferent signals involved in visceral reflexes.03/05/60 33
Conscious sensations Posterior Column–Medial Lemniscal pathway The chief functions of the posterior column–medial lemniscalpathway are those of conscious proprioception and discriminativetouch. Together, these attributes provide the parietal lobe with aninstantaneous body image so that we are constantly aware of theposition of body parts (proprioception) and limb movement(kinesthesia). Without this informational background, the execution ofmovements is severely impaired.03/05/60 34
Sensory cortex Posterior (dorsal) column–medial 3rd lemniscus pathway 2nd 3rd order neurone/Nucleus of the thalamus 1st VPL (ventral posterolateral nucleus) Trigeminal lemniscus 03/05/60 VPM (ventral posteromedial nucleus) sensory decussation crossed the midline Medial lemniscus 2nd order neurone Nucleus gracilis and Nucleus cuneatus cuneate fasciculus (fasciculus cuneatus) T6 gracile fasciculus (fasciculus gracilis) 1st order neurone The dorsal root ganglia Sensory receptor 35
The sensory ataxia Sensory gait 36 Romberg test03/05/60
Conscious sensations Spinothalamic pathway Fibers within the lateral spinothalamic tract were consideredto carry only pain and thermal information, whereas the anterior spinothalamic tract was thought to beconcerned only with nondiscriminative touch.03/05/60 37
Spinothalamic pathway (anterolateral system ALS) Pain & Temp Lateral Spinothalamic tractGross touch 38Anteriorspinothalamic tract 03/05/60
Spinothalamic pathway (LSTT) Sensory cortex 3rd3rd order neurone/Nucleus of the thalamus VPL (ventral posterolateral nucleus) LSTTCross midline at antr white commissure 2nd order neurone Posterior funicular gray (Nucleus proprius)2 Lissauer tract 2nd1 1st 1st order neurone 03/05/60 39 The dorsal root ganglia Pain & temp receptor
Central and Peripheral overlap of Lissauer’s tractT8 T9 2 1Lesion T10 3 X T11 T2 Rt Lt 40 1. One segment lesion cause………………………………..................... 2. Hemisection of the spinal cord………………………………………….. 3. Trans-section of the spinal cord………………………………………….03/05/60
Spinothalamic pathway (ASTT) Sensory cortex 3rd3rd order neurone/Nucleus of the thalamus VPL (ventral posterolateral nucleus) ASTTCross midline at antr white commissure 2nd order neurone Posterior funicular gray (Nucleus proprius)6-8 Medial division 2nd6-8 1st 1st order neurone 03/05/60 41 The dorsal root ganglia Gross touch
Somatotopic pattern of white fiber03/05/60 42
The cortex contains a somatotopic representation of the body surface (a homunculus, or “little man”)03/05/60 43
Referred pain is the phenomenon whereby noxious stimuli that originate in a visceralstructure, such as the heart or the stomach, are perceived by the patient as pain arisingfrom a somatic portion of the body wall.Visceral pain is transmittedby sympathetic sensoryfibers and is typically Angina pain T1-5referred to those somaticstructures whose afferentsenter the cord via the sameposterior roots.03/05/60 44
Nonconscious sensations Spinocerebellar pathways 4 fiber tracts run from the spinal cord to the cerebellum • Posterior spinocerebellar • Cuneocerebellar • Anterior spinocerebellar • Rostral spinocerebellar03/05/60 45
Anterior spinocerebellar Cuneocerebellar Rostral spinocerebellar Posterior spinocerebellar Post-SC DRG tract 46 Ant-SC tract03/05/60
Posterior (Dorsal) Spinocerebellar Tract Sup. cerebellar peduncle lower limb and lower trunk Inf. cerebellar peduncle Cuneocerebellar t. Cerebellar cortex Lateral Restiform body cuneate nu. Posterior Spinocerebellar tract Nucleus dorsalis (ipsilateral*) Posterior Spinocerebellar t. 2nd order neurone 47Nu. Dorsalis (dorsal nu. of Clarke) (C 8 - L 3 ) Medial division Anterior Spinocerebellar t. 1st order neurone The dorsal root ganglia03/05/60 Golgi tendon, muscle spindle
Cuneocerebellar Tract Sup. cerebellar peduncle Upper limb Inf. cerebellar peduncle Cuneocerebellar t. Cerebellar cortex Lateral Restiform body cuneate nu.Cuneocerebellar tract (ipsilateral*) Nucleus dorsalis Posterior 2nd order neurone (above C 8 ) Spinocerebellar t. Lateral cuneate nucleus 48 Medial division Anterior Spinocerebellar t. 1st order neurone The dorsal root ganglia03/05/60 Golgi tendon, muscle spindle
Anterior (ventral) Spinocerebellar Tract Sup. cerebellar peduncle Lower half of the cord Inf. cerebellar peduncle Cuneocerebellar t. Cerebellar cortex Lateral Superior cerebellar peduncle cuneate nu. Re-cross Nucleus dorsalisAnterior Spinocerebellar tract Posterior Spinocerebellar t.Cross or uncross at antr white commissure 49 2nd order neurone Anterior Spinocerebellar t.***L3 to L5 Spinal border cellsMedial division 1st order neurone The dorsal root ganglia03/05/60 Golgi tendon, muscle spindle
Rostral Spinocerebellar Tract Sup. cerebellar peduncle upper half of the cord Inf. cerebellar peduncle Cuneocerebellar t. Cerebellar cortex LateralMainly Inferior cerebellar peduncle cuneate nu. Some fiber to superior cerebellar peduncle Nucleus dorsalis Posterior (ipsilateral Uncross*) Spinocerebellar t. Rostral Spinocerebellar tract 50 2nd order neurone Anterior Spinocerebellar t.*** Lamina VII of the cervical enlargement (C4 to C8)Medial division 1st order neurone The dorsal root ganglia03/05/60 Golgi tendon, muscle spindle
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