spinal cord=dr.khalid latifawan

SPINAL CORD

SPINAL CORD

Brain and spinal cord are parts of the central Nervous system , except them everything else comes under P.N.S.

It performs two main functions 1 -conduction of impulses to and from

the brain 2 -it processes sensory information in a

limited manner, making it possible for the cord to initiate stereotyped reflex actions ( spinal reflexes with out input from higher centers in the brain).

SPINAL CORD

Spinal cord weighs about 30 grams , comprises 2% of the

adult brain weight 1 cm In diameter Average length 45 cm in male

42 cm in female

SPINAL CORD

A. LOCATION B.ATTACHMENTS –denticulate ligaments Suspend and

Anchor the spinal cord within the DURAL SAC and arises from the vascular pia matter

- filum terminale -spinal nerve roots

GENERAL STRUCTURE OF SPINAL CORDExtension : foramen magnum _ Ist or IInd

lumber vertebraUp till 3rd month of gestation period Spinal cord = vertebral column Later on vertebral column grow at a faster

rate therefore the spinal cord does not extend the entire length of the vertebral column in the adult.

GENERAL STRUCTURE OF SPINAL CORD


Conus medullaris = Tip of spinal cord filum terminale = a pial filament

Extending from C. medullaris to the end of dural sac. With which it fuses.

Which extend up to the level of L1 and L2 31 pairs of mixed (motor and sensory )

spinal nerves which passes through intervertebral forminae except C1


Cervical nerves C1-C8Thoracic nerves T1-T12Lumbar nerves L1-L5Sacral nerves S1-S5

Cocygeal nerve


Each portion of the cord that gives rise to a pair of spinal nerves is called a spinal segment

At the end of spinal cord,the descending lumber and sacral roots has the appearance of a horse tail and therefore ---- cauda equina

Cervical enlargement ----- upper limb (C5-T1) Brachial plexusLumber enlargment ------ lower limb(L1-S2) Lumbo sacral plexus

SPECIAL CONSIDERATION

-The C1 and the cocceygeal nerves usually have no dorsal (sensory) roots and no

corresponding dermatome

-C1 passes between the atlas and skull-C2 between atlas and axis vertebrae

-All cervical spinal nerves passes above the vertebrae

FUNCTIONAL COMPONENTS OF SPINAL NERVE

COMPONENTS AND BRANCHES OF SPINAL NERVE

Formation dorsal intervertebral ventral foramina mixed

nerve

a. Dorsal rootb. (DRG) c. Ventral root Spinal nerve and its

rami


A. dorsal primary ramus innervate the skin and muscles of back

B. Ventral primary ramus innervate the ventral lateral muscles , skin ,trunk extremities and visceral organs

C. Gray communicating ramus contain unmyelinated post ganglionic nerve fibers, which are part of all the spinal nerves


D. White communicating ramus contains myelinated Preganglionic sympathetic fibers and myelinated GVA

-are found only in THORACOLUMBER segments of the spinal cord T1-L3

MENINGES

GREEK=membrane SINGULAR meninex PIA MATTER , LATIN=faithful,

gentle, pious ARACHNOID MATTER, GREEK=spider or

web DURA MATTER, LATIN=tough

MENINGES OF THE SPINAL CORD

DURA MATER : of the spinal cord does not fuse to the bones of the surrounding vertebrae. small fat filled epidural space----- cushion the spinal cord. Dura mater encloses cauda equina and forms a covering around the filum terminale . It also extends laterally to blend with connective tissue of each spinal nerve.

MENINGES OF THE SPINAL CORD

ARACHNOID: mater forms a close lining of the dura mater . The sub arachnoid space contains C.S.F. It is largest in the region of the cauda equina.

PIA MATER contains a rich network of blood vessels.

Spinal cord is held in a some what fixed position with in the meninges by fibrous bridges that cross the subarachnoid spaces joining pia mater arachnoid and dura mater. The heaviest of the bridges are the denticulate ligaments.

COMPOSITION OF SPINAL CORD

Like brain spinal cord consists of areas of white – myelinated processes of neurons and gray – nerves cell bodies and unmyelinated

inter neuronal nerve fiber.Neuroglia the supportive cells are present in both

white and gray mater.In contrast to cerebrum and cerebellum the gray

mater is centrally located and is surrounded by white mater.

Gray mater Letter H or butterfly shape


Gray commisure Central canal is in the gray commisurePosterior (dorsal) hornsAnterior (ventral ) hornsIn thoracic and lumber regions (T1_L3)Gray mater also include lateral horns.


Alar plate consist of post horns composed of axons of

sensory neurons of spinal nerve and inter neurons that transmit sensory information.


some of the axons of sensory neurons enter the white matter of the post. area of spinal cord, these axons then travel to higher level of the cord or to the brain.

Other sensory axons enter the gray matter and make direct synapses either with neurons (motor) thus forming as spinal reflex arc, or with inter neurons. These interneurons may in turn synapses with anterior horn motor neurons at the same level, pass higher or lower levels with in the spinal cord or travel all the way up to various regions in the brain.


BASAL PLATE consist of

ANTERIOR HORN-somatic motor neurons. Axon leaves the spinal cord and enter a spinal nerve.

LATERAL HORN – visceral motor neurons


Dorsal and ventral roots of spinal nerve from each segment unite to form a spinal nerve.

Dorsal root= axons of somatic sensory and visceral sensory neurons (which are present in the dorsal root ganglia)

Ventral root = axons of neurons located in the anterior and lateral horn of gray matter. The ventral root therefore contribute process of both somatic motor and visceral motor (autonomic) neurons to the spinal nerve.

FUNCTIONAL COMPONENTS OF A SPINAL NERVE

WHITE MATTER OF THE SPINAL CORD: myelinated axons and travel in three direction1- UP the spinal cord to higher level in the

cord or brain.2-DOWN the spinal cord from the brain or

higher levels of the cord.3-ACROSS the cord , transmitting impulses

from one side to the other.white matter of each half of spinal cord is

divided by the gray matter into three areas

Post funiculus Lateral funiculusAnt funiculusWith in the funiculi there are small bundles

of nerve fibers called fasiculi = tracts.A tract carry similar types of impulses to a

specific destination and are composed of the conductive processes of neurons.

Ascending sensory = to brainDescending motor = from brain down to the

motor neurons in the anterior or lateral gray horns of spinal cord.

Most of the tracts have descriptive names that indicate where they begin and where they terminate.

Ascending spinal tract (sensory tracts)These tracts of spinal cord carry afferent

(sensory)

Impulses from peripheral sensory receptors to various centers in the brain.

These tracts generally contain three successive neurons called

1st order (dorsal root ganglia)2nd order (spinal cord or medulla)3rd order (thalamus) ↓ ↓ cerebral cortex

Majority of the ascending spinal tract cross to the other side of central nervous system either at the level of the entry into spinal cord or few segments above the entry level or within the medulla.

Major sensory (Ascending)tracts are1- fasciculus gracilis2- fascilculus cuneatus3- spinothalaamic tract4- spino cereberullar tract5 -spino reticular 6-spino mesencephalic

Fasciculus gracilis } proprioception fine

touchFascilis cuneatus

lateral spinothalamic } pain and temperature

Ant spinothalamic } touch and pressure

Four spino cerebellar tract Anterior spino cerebellar tract Posterior spino cerebellar tract( unconscious proprioception )

Descending (motor ) spinal tracts Brain lower motor neuronsThat regulate the activity of skeletal

muscles i.e voluntary skilled motor activity (limbs)

All of these tracts cross form one side of CNS to the other and they all contain two or three consecutive neurons .

Two types of descending spinal tracts 1-pyramidal tracts

2-extra pyramidal tracts

THANK YOU

1-PYRAMIDAL TRACTS

Pyramidal tracts = corticospinal tract = uper motor neurons

crossing at medulla to form lateral corticospinal tract 80 % remaining 20 % form anterior conticospinal tract which are uncrossed .

Some of the nerve s fibers cross at the level at which they synapse with lower neurons (motor or sensory)

Lateral Corticospinal motor stimuli to Anterior Corticospinal to skeletal muscles lateral corticospinal tracts are major tracts involved

in the voluntary control of skeletal muscles and extend whole length of spinal cord while anterior

corticospinal is up to thoracic level.

2-EXTRA PYRAMIDAL TRACTS

The remaining motor tracts are called extra pyramidal tracts

They begin from various nuclei in the brain stem and influence

Muscular actionCo-ordinationBalanceVisual and auditory stimuli and other

functions

- Rubro spinal tract (crossed)- Vestibulo spinal tract ( uncrossed)- Tecto spinal tract (crossed)- Olivo spinal tract

Over lapping of corticospinal ad extra pyramidal tracts clean separation is not possible.

Pyramidal spinal tract = movement of the body

Extra pyramidal spinal tract = posture and balance and to modify muscular contraction.

spinal cord=dr.khalid latifawan

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