Dr. Ahmed Fathalla Ibrahim

TRANSVERSE SECTIONTRANSVERSE SECTION

(T1-L3)

GREY MATTER OF SPINAL GREY MATTER OF SPINAL CORDCORD

• DORSAL HORN: DORSAL HORN: contains sensory contains sensory neuronesneurones

• VENTRAL HORN: VENTRAL HORN: contains motor contains motor neurones (lower motor neurones):neurones (lower motor neurones):

1.1. Alpha motor neurones:Alpha motor neurones: innervate extrafusal muscle fibers

2.2. Gamma motor neurones:Gamma motor neurones: innervate intrafusal muscle fibers

• LATERAL HORN (T1-L3): LATERAL HORN (T1-L3): contains contains autonomic neuronesautonomic neurones

LAMINATION OF GREY MATTERLAMINATION OF GREY MATTER

NUCLEINUCLEI

NUCLEI OF DORSAL HORNNUCLEI OF DORSAL HORN

Substantia gelatinosa: Substantia gelatinosa: • Site: Site: tip of dorsal horn, laminae I-III• Level:Level: all levels• Function:Function: contains second order second order

neurones for pathway of pain & neurones for pathway of pain & temperature sensations from the temperature sensations from the body to sensory cortex (lateral body to sensory cortex (lateral spinothalamic tract)spinothalamic tract)

NUCLEI OF DORSAL HORNNUCLEI OF DORSAL HORN

Nucleus proprius:Nucleus proprius:• Site: Site: ventral to substantia gelatinosa,

laminae IV-V• Level:Level: all levels• Function:Function: contains second order second order

neurones for pathway of crude neurones for pathway of crude touch sensation from the body to touch sensation from the body to sensory cortex (ventral sensory cortex (ventral spinothalamic tract)spinothalamic tract)

NUCLEI OF DORSAL HORNNUCLEI OF DORSAL HORN

Nucleus dorsalis (Clarke’s column):Nucleus dorsalis (Clarke’s column):• Site: Site: base of dorsal horn, lamina VII• Level:Level: C8 – L3• Function:Function: contains second order second order

neurones for pathway of neurones for pathway of proprioceptive &exteroceptive proprioceptive &exteroceptive sensations to cerebellum (dorsal sensations to cerebellum (dorsal spinocerebellar tract)spinocerebellar tract)

NUCLEI OF VENTRAL HORNNUCLEI OF VENTRAL HORN

Medial group:Medial group:• Site: Site: medial part of ventral horn, lamina

VIII

• Level:Level: all levels

• Function: Function: contains cell bodies of neurones innervating axial musclesaxial muscles

NUCLEI OF VENTRAL HORNNUCLEI OF VENTRAL HORNLateral group:Lateral group:• Site: Site: lateral part of ventral horn, lamina IX• Level:Level: all levels: 1. More prominent in cervical & lumbosacral

segments2. Represented by one nucleus in thoracic

segments• Function: Function: 1. In cervical & lumbosacral segments: contains

cell bodies of neurones innervating limblimb musclesmuscles

2. In thoracic segments: contains cell bodies of neurones innervating intercostal musclesintercostal muscles

NUCLEI OF VENTRAL HORNNUCLEI OF VENTRAL HORN

Phrenic nucleus:Phrenic nucleus:• Site: Site: central part of ventral horn,

lamina IX

• Level:Level: C3 – C5 • Function: Function: contains cell bodies of

neurones innervating the diaphragmthe diaphragm

NUCLEI OF VENTRAL HORNNUCLEI OF VENTRAL HORN

Accessory nucleus:Accessory nucleus:• Site: Site: base of ventral horn, lamina

IX

• Level:Level: C1 – C5 • Function: Function: contains cell bodies of

neurones innervating sternomastoid & sternomastoid & trapeziustrapezius

NUCLEI OF LATERAL HORNNUCLEI OF LATERAL HORN

Intermediolateral nucleus:Intermediolateral nucleus:• Level:Level: T1 – L3 • Function: Function: contains preganglionic preganglionic

sympathetic neuronessympathetic neurones• N.B.: the nucleus is present in S2-S4 N.B.: the nucleus is present in S2-S4

segments (with no lateral horn) & segments (with no lateral horn) & contains preganglionic contains preganglionic parasympathetic neuronesparasympathetic neurones

WHITE MATTER OF SPINAL WHITE MATTER OF SPINAL CORDCORD

• DORSAL COLUMN (FUNICULUS)DORSAL COLUMN (FUNICULUS)

• LATERAL COLUMN (FUNICULUS)LATERAL COLUMN (FUNICULUS)

• VENTRAL COLUMN (FUNICULUS)VENTRAL COLUMN (FUNICULUS)

The white matter is formed of tracts:The white matter is formed of tracts:

1.1. AscendingAscending

2.2. Descending Descending

3.3. Both ascending & descendingBoth ascending & descending

TRACTSTRACTS

MAIN ASCENDING TRACTSMAIN ASCENDING TRACTSDORSAL COLUMN TRACT:DORSAL COLUMN TRACT:• Site:Site: occupies the whole dorsal columnthe whole dorsal column, gracile tract

is medialmedial to cuneate tract• Level:Level: 1.1. Gracile tractGracile tract: : all levels2.2. Cuneate tractCuneate tract: : from T6 to C1• Second order neurones:Second order neurones: Gracile & cuneate nuclei Gracile & cuneate nuclei

in medulla oblongatain medulla oblongata• Types of fibers:Types of fibers: proprioceptive & discriminative proprioceptive & discriminative

(fine) touch fibers(fine) touch fibers1.1. Gracile tractGracile tract: : from lowerlower half of body2.2. Cuneate tractCuneate tract: : from upperupper half of body• Termination:Termination: sensory cortexsensory cortex

MAIN ASCENDING TRACTSMAIN ASCENDING TRACTSSPINOTHALAMIC TRACTS:SPINOTHALAMIC TRACTS:• Site: Site: 1.1. Lateral spinothalamicLateral spinothalamic: lateral : lateral column2.2. Ventral spinothalamicVentral spinothalamic: ventral : ventral column• Level: Level: all levels• Second order neurones: Second order neurones: Substantia Substantia

gelatinosa gelatinosa (lateral), (lateral), nucleus proprius nucleus proprius (ventral)(ventral)

• Types of fibers: Types of fibers: exteroceptive fibers from exteroceptive fibers from bodybody

1.1. Lateral spinothalamicLateral spinothalamic: pain & temperature: pain & temperature2.2. Ventral spinothalamicVentral spinothalamic: non discriminative : non discriminative

(crude) touch(crude) touch• Termination: Termination: sensory cortexsensory cortex

MAIN ASCENDING TRACTSMAIN ASCENDING TRACTSSPINOCEREBELLAR (DORSAL & VENTRAL) SPINOCEREBELLAR (DORSAL & VENTRAL)

TRACTS:TRACTS:• Site: Site: both tracts are located in lateral both tracts are located in lateral

columncolumn• Level: Level: all levels• Second order neurones:Second order neurones:1.1.Dorsal spinocerebellarDorsal spinocerebellar: Clarke’s column: Clarke’s column2.2.Ventral spinocerebellarVentral spinocerebellar: laminae V-VII: laminae V-VII• Types of fibers: Types of fibers: proprioceptive & proprioceptive &

exteroceptive fibers from bodyexteroceptive fibers from body• Termination: Termination: cerebellumcerebellum

DESCENDING TRACTSDESCENDING TRACTS

CORTICOSPINAL TRACTS:CORTICOSPINAL TRACTS:• Site:Site:1.1.Lateral corticospinal:Lateral corticospinal: lateral lateral column2.2.Vental corticopsinal:Vental corticopsinal: ventral ventral column• Level: Level: all levels• Origin: Origin: motor cortex motor cortex • Function: Function: control of voluntary, discrete voluntary, discrete

& fine& fine movements, especially those of distal parts of limbs

DESCENDING TRACTSDESCENDING TRACTS

RUBROSPINAL TRACT:RUBROSPINAL TRACT:• Site: Site: lateral lateral column,

intermingled with lateral corticospinal tract• Level: Level: all levels• Origin: Origin: red nucleus of midbrainred nucleus of midbrain• Function: Function: excitatory effect over excitatory effect over

tone of limb flexor musclestone of limb flexor muscles

DESCENDING TRACTSDESCENDING TRACTS

TECTOSPINAL TRACT:TECTOSPINAL TRACT:• Site: Site: ventral ventral column• Level: Level: in cervical region in cervical region • Origin: Origin: superior colliculus of superior colliculus of

midbrainmidbrain• Function: Function: mediates reflex mediates reflex

movements in response to movements in response to visual stimulivisual stimuli

DESCENDING TRACTSDESCENDING TRACTSVESTIBULOSPINAL TRACTS:VESTIBULOSPINAL TRACTS:• Site: Site: both tracts are located in ventral ventral

column• Level: Level: all levels all levels • Origin:Origin:1.1. Lateral vestibulospinalLateral vestibulospinal: lateral vestibular : lateral vestibular

nucleus in pons & medulla nucleus in pons & medulla 2.2. Medial vestibulospinalMedial vestibulospinal: : forms the the

descending fibers of the medial descending fibers of the medial longitudinal fasciculuslongitudinal fasciculus

• Function: Function: control body posture & balancecontrol body posture & balance

DESCENDING TRACTSDESCENDING TRACTS

RETICULOSPINAL TRACTS:RETICULOSPINAL TRACTS:• Site: Site: both tracts are located in ventral ventral

column• Level: Level: all levels all levels • Origin:Origin:1.1.Medial reticulospinalMedial reticulospinal: pontine : pontine reticular

formation2.2.Lateral reticulospinalLateral reticulospinal: medullary : medullary reticular

formation3.3.Function: Function: inhibitory or excitatory effect on inhibitory or excitatory effect on

muscle tonemuscle tone

BOTH ASCENDING & BOTH ASCENDING & DESCENDING TRACTSDESCENDING TRACTS

• FASCICULUS PROPRIUS FASCICULUS PROPRIUS (INTERSEGMENTAL TRACT): (INTERSEGMENTAL TRACT): occupies a occupies a narrow band immediately peripheral to narrow band immediately peripheral to grey matter, serves for coordination grey matter, serves for coordination between upper & lower limb muclesbetween upper & lower limb mucles

• LISSAUER’S TRACT: LISSAUER’S TRACT: lies superficial to the lies superficial to the tip of dorsal horn, by the help of this tract,tip of dorsal horn, by the help of this tract, exteroceptive fibers can establish synaptic exteroceptive fibers can establish synaptic contacts over several segments of spinal contacts over several segments of spinal cordcord

N.B.: TRACTSN.B.: TRACTS

N.B.: TRACTSN.B.: TRACTSASCENDING:ASCENDING:1.1. Dorsal column:Dorsal column: contains only dorsal column

tracts2.2. Ventral column:Ventral column: contains ventral

spinothalamic tract3.3. Lateral column:Lateral column: contains the rest of tractsDESCENDING:DESCENDING:1. All desending tracts are present in ventral ventral

columncolumn EXCEPT: lateral corticospinal & rubrospinal tracts (present in lateral columnlateral column)

2. No descending tract present in dorsal column

N.B.: TRACTSN.B.: TRACTS

• All ascending tracts have same All ascending tracts have same first order neurones: first order neurones: cells of dorsal cells of dorsal root ganglionroot ganglion

• All descending tracts have same All descending tracts have same termination: termination: cells of ventral horn cells of ventral horn (lower motor neurones)(lower motor neurones)