spinal cord

SPINAL CORD

INTRODUCTION Structure Function Tracts

STRUCTURE OF SPINAL CORDLong :- Men=45cm(18inch) Women=43cm(17inch)Width :- Cervical and lumbar = 1/2inch thick Thoracic area = 1/4inch thick Begins from occipital bone until L1&L2 the end of spinal cord = filum terminal

LAYERS OF SPINAL CORD Meninges

Epidural = External of dura(fat-fil) Subdural space = Serous fluid Subarachnoid = Between pia and arachnoid (CSF

filled)

Dura mater (dural sheath)=outermost

Arachnoid’s mater = thin,movable

Pia mater=forms filum terminal,denticulate ligament

Connective tissue

membranes

Subdural space

Subarachnoid

Epidural

Spinal segment = spinal nerve Spinal nerve has two roots Dorsal root ganglion = swelling like structure

Anterior root= ventral root

Posterior root=dorsal root

SPINAL NERVE

Spinal cord have 31 segment 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal

The spinal segments that contribute to the nerve of the upper are enlargement to the form cervical and lumbar enlargements

VERTEBRAE AND CORRESPONDING SPINAL SEGMENT RELATIONSHIP vertebrae spinal segments

C1 to C4 (upper cervical) same

C4 To C7 (lower cervical) +1

T1 to T7 +2

T7 to T9 +3

T10 L1,L2

T11 L3,L4

T12 L5,S1

L1 sacral and coccygeal nerve

ARTERIAL SUPPLY Spinal Arteries :- Anterior (1) & Posterior (2) Spinal Artery from

Vertebral artery Radicular Arteries :- Segmental arteries from Vertebral,Ascending

Cervical,Intercostal and Lumbar Artery Venous Drainage veins :- Longitudinal & Radicular Veins

Intervertebral veins Internal Vertebral Venous Plexus external vertebral venous plexus segmental veins

INTRODUCTION OF SPINAL TRACT Tract is a bundle of nerve fibers (within

CNS) having the same :- Origin Course Destination Function

The name of the tract = origin = destination

The axons within each tract are grouped according to the body region innervated

Long tracts at white matter Short tracts at gray matter There are 2 types of tract :- Ascending tract=Sensory Descending tract=Motor

CROSS OVER Decussation is the cross-over of the

tract from one side to the other. Therefore,there are instances where the

left side of the body is controlled by the right brain hemisphere.

Decussation occurs at different locations for each tracts.

ASCENDING TRACT

Ascending Spinal Tracts

SENSORY PATHWAYS Contain a sequence of 3 neurons

from the receptor to the cerebral cortex

1st order neuron: Sensory neuron that delivers

information from the receptor to the CNS.

2nd order: Has cell body in the spinal cord

or medulla oblongata Axon decussate

3rd order neuron: Has cell body in thalamus Axon terminates on cerebral

cortex ipsilaterally

1

2

3

Modality: Discriminative Touch Sensation Conscious

Proprioception Receptor: Most receptors except free nerve endings

Ist Neuron: Dorsal Root Ganglion (Spinal Ganglion) Dorsal Column Nuclei (Nucleus Gracilis Thalamus (VPLc) ,Corona Radiata

Termination: Primary Somesthetic Area (S I)

Posterior White Column-Medial Lemniscal Pathway

LATERAL SPINOTHALAMIC TRACT

Modality:pain and thermal sensations.

Ist Neuron : dorsal horn 2nd Neuron: mostly in the

nucleus proprius), decussate within one segment by passing through the ventral white commissure

3rd Neuron: ventral posterior nucleus of the thalamus

Thalamic neurons project to the somatosensory cortex

ANTERIOR SPINOTHALAMIC TRACT

Modality:non- discriminative touch and pressure

Ist Neuron : dorsal horn 2nd Neuron: nucleus

proprius,crossing to opposite side by passing through the ventral white commissure

3rd Neuron: in ventral posterior nucleus of the thalamus

Thalamic neurons project to the somatosensory cortex

VENTRAL SPINOCEREBELLAR TRACTS

Ist Neuron neuron lie in base of the dorsal horn of the lumbosacral segments

cross to opposite side, ascend as far as the midbrain

2nd Neuron: terminating in the cerebellar cortex

Both spinocerebellar tracts convey sensory information to the same side of the cerebellum

POSTERIOR SPINOCEREBELLAR TRACTS

Info:Present only above level L3

Ist Neuron in Clark’s column

2nd Neuron: terminate ipsilaterally in the cerebellar cortex

DESCENDING TRACT

*PYRAMIDAL*EXTRAPYRAMIDAL

MOTOR PATHWAYS 2 Sequence of neuron(from cerebral

cortex/brain stem – muscle) Upper Motor Neuron(UMN)

o Spinal cord -> braino Cell body cross over before terminate on

lower motor neuron Lower Motor Neuron(LMN)

o Spinal cord -> muscle o Cell body pass through posterior root of

spinal nerve

DESCENDINIG TRACT

PYRAMIDAL TRACT(DIRECT)

ANTERIOR CORTICOSPINAL

TRACT

LATERAL CORTICOSPINAL

TRACT

EXTRAPYRAMIDAL TRACT

(INDIRECT)

RETICULOSPINAL

TRACT

VESTIBULOSPINALTRACT

TECTOSPINALTRACT

RUBROSPINALTRACT

PYRAMIDAL TRACT

(DIRECT PATHWAY)

CORTICOSPINAL TRACTFunction:voluntary movement

: fine skill movement Anterior corticospinal tract

o Origin:motor cortex (4,6)

:somatosensory cortex (1,2,3)o Course:pass through midbrain(cerebral peduncle) pyramid of medulla oblongatao Termination: anterior white column

Lateral corticospinal tracto Origin: motor cortex (4,6)

:somatosensory cortex (1,2,3)o Course: pass through midbrain(cerebral peduncle)

(cross over)

pyramid of medulla oblongata

o Termination: lateral white columno Corticobulbar innervate cranial nerves motor nuclei of CNS

EXTRAPYRAMIDAL TRACT(INDIRECT PATHWAY)

RETICULOSPINAL TRACT Function: coordination of voluntary and reflex movement

: control of muscle tone : control of respiration and diameter of blood vessel Origin: Reticular formation (pontine & medulla) Course :pass through medial pontine lateral medulla Termination: ventral funniculus

TECTOSPINAL TRACT Function: coordination of head and neck

to the visual & audio stimuli Origin : superior colliculus Course : pass through periaquductal (cross)

Dorsal tegmental

Termination: Anterior median fissure

(cervical area)

RUBROSPINAL TRACT Function : controls flexor muscle tone Origin : Red nucleus Course :cross to (lower cervical segment) Termination: lateral white column

VESTIBULOSPINAL TRACT Lateral vestibulospinal tract Function: control extensor muscle tone : antigravity maintenance of posture Origin : lateral vestibular (Derter’s) nucleus Termination :ventral funniculus

• Medial vestibulospinal tractFunction: control movement of head :maintain equilibrium Origin:medial vestibular nucleusTermination: ventral funniculus + medial funniculus