spinal,cord,nerve,plexii

8/9/2019 spinal,cord,nerve,plexii

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Spinal Cord and Nerve

Plexii

By

DR. T


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1. Organization

- General

- Cauda equina

- Meninges2. Structure

Grey matter

White matter

3. Blood supply

4. Spinal nerves

- Typical n.

- Components

Part I: Spinal cord


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1. Organization

Cauda equina Meninges


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2. Structure: Grey matter Components: Nerve cells, Processes, Neuroglia,

Blood vessels

Grey columns: Anterior, Posterior, Transverse,

Lateral


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Grey columns:

Anterior:

Medial group: skeletal

muscles of the neck and

trunk

Central group: cervicaland lumbosacral

segments & contains thephrenic, asccessory and

lumbosacral nuclei

Lateral group: cervical

and lumbosacral areasinnervating skeletalmuscles of the limbs

Posterior:

Substantia gelatinosa:concerned with pain,temperature and touch

Nucleus proprius: fibersfrom white posteriorcolumn associated withproprioception, 2-piontdiscrimination andvibration

Nucleus dorsalis (Clarkscolumn) from C8 L3/4proprioceptive endings inspindles

Visceral afferent nucleusfrom T1 L3 receivesvisceral afferent

information


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Grey columns (cont.)

Transverse:

Contains central canal

that starts in the MO,

Inferiorly expands in

the conus medullaris

as the terminal

ventricle: CSF &

ependyma

Lateral:

From T1L2/3

Give rise to

preganglionicsympathetic fibers

Similar group in S2-4give rise topreganglionicparasympathtic fibres


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2. Structure: White matter

Mixture of myelinated nerve fibers, neuroglia and

blood vessels

Ascending tracts

Descending tracts

Ascending and descending tracts with the same

origin, course and termination: Fasciculus

Intersegmental tracts


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Ascending tracts: Sensory, contain 1st, 2nd and 3rd order neurons

Pathways for temperature, pain, proprioception

Examples: Spinothalamic tract (lateral & anterior,

fasciculus gracilis and cuneatus); Spinocerebellar tract

(anterior & posterior); Cuneocerebellat tract.

Other: Spinotectal, spinoreticular, spino-olivary, visceral

sensory


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Descending tracts:

White matter from the supraspinal centers with 1st, 2nd and

3rd order motor neurons

Examples: Corticospinal, reticularspinal, tectospinal,

rubrospinal, vestibulospinal, olivospinal, descending

autonomic


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3. Blood supply: Spinal arteries From vertebral, posterior intercostal, lumbar, lateral sacral, ascending

cervical, deep cervical, iliolumbar aa.

Posterior spinal a. in close association to posterior spinal roots, but isinsufficient to supply the spinal cord alone

Anterior spinal a. unite to for a single artery on the median fissure of the

spinal cord.


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Spinal arteries (cont.) Radicular a. reinforce the spinal arteries by entering

through the intervertebral foramina Larger anterior radicular arteries: A. radicularis magna

(artery of Adamkiewicz) from the left an intersegmental

branch of the descending aorta, that supplies 2/3rds of the

spinal cord


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3. Blood supply: Venous drainage

Internal (anterior & posterior) venous plexus

External venous plexus (anterior & posterior)

Basivertebral and intervertebral veins.


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4. Typical spinal nerve Posterior (dorsal) root: Supplies synovial joints of the

vertebral column, deep muscles of the back & overlying

skin. Posterior root ganglia: Sensory, unipolar with

satellite cells.

Anterior (ventral) root: Supplies the remaining areas:

anterior & lateral regions of the trunk and limbs


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Part II: Nerve plexii

1. Cervical plexus

2. Brachial plexus

3. Lumbar plexus

4. Sacral plexus


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Concepts of nerve plexii

Peripheral nerve that divide and join otherperipheral nerves to form a network

Plexus permits individual nerve fibers to passfrom one peripheral nerve to another allowing

redistribution of nerves Peripheral nerve: Bundle of nerve fibers in a

sheath, can be cranial or spinal

Ganglion: Collection of nerve bodies outside theCNS

T2 L1 segmental innervation of skin andmuscles

Other areas: nerve plexii


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1. Cervical plexus (C1 C4)

Ansa cervicalis:

superior (C1) & inferior

(C2,3) radix

Minor occipital n. (C2)

Greater auricular n.

(C2,3)

Transverse cervical n.

(C2,3)

Supraclavicular n.

(C3,4)

Deep branches

Phrenic n. (C3,4,5)


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1. Cervical plexus in situ


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2. Brachial plexus (C5 T1)

Roots (C5-T1) Trunks: Upper (C5,6),

middle (C7), lower(C8,T1)

Divisions: anterior &posterior

Cords: Lateral cords formed by

the anterior divisions ofthe upper end middle

trunks Medial cord formed by

the anterior division ofthe lower trunk

Posterior cord formed bythe posterior division of

the middle, lower & uppertrunks


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3. Lumbar plexus (L1 L4)

Iliohypogastric n. (L1)

Ilioinguinal n. (L1)

Genitofemoral n.

(L1,2)

Lateral cutaneous n.

of thigh (L2,3)

Femoral n. (L2-L4)

Obturator n. (L2-L4)


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4. Sacral plexus (L4 S4)

To LL and gluteal regions:

Sciatic n.

Superior gluteal n. (L4-S1)

Inferior gluteal n. (L5-S1)

Posterior cutaneous nerve ofthe thigh (S1-3)

To quadriceps femoris (L4 S1)

To obturator internus (L5,S1)

To Pelvis:

Pudendal nerve (S2-4) Nn. Splanchini pelvini (S2-4)

To levator ani & coccygeus

(S3-4)

Perineal branch (S4)

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