2

CONTENTS OF VERTEBRAL

CANAL AND ITS APPLIED

ASPECTS

(superior view)

Vertebral Column

� Central bony pillar of the body.

� Supports the skull, pectoral girdle, upper

limbs and the thoracic cage.

� Within its cavity lie the spinal cord, the roots

of the spinal nerves, the covering-meninges.

� Composed of 33 vertebrae: 7 cervical, 12

thoracic, 5 lumbar, 5 sacral, 4 coccygeal.

� It is a flexible structure made up of

fibrocartilage called intervertebral discs.

8

VERTEBRAL CANAL

� The vertebral canal is formed by placing the vertebra in a sequence, that their vertebral foraminae are lie one below the other forming continuous canal

9

The vertebral canal

� The vertebral canal is bounded

anteriorly by the vertebral bodies and

the intervertebral discs, each

covered by the posterior longitudinal

ligament, which is continuous from

the back of the body of the axis to

the sacrum.

10

The vertebral canal

� Posteriorly it is bounded

by the laminae,

ligamenta flava and the

arch of the vertebra.

� The vertebral canal is

usually larger in the

cervical and lumbar

regions.

11

CONTENTS OF VERTEBRAL CANAL

� The contents –from outwards;

� 1.epidural or extra dural space

� 2.thick dura mater or pachymenix

� 3.subdural capillary space

� 4.delicate arachnoid mater

� 5.wide subarachnoid space containing CSF

� 6.firm pia mater .The Arachnoid and Piamater together-leptomeninges

� 7.spinal cord and the cauda equina

� 8.Blood supply [arteries and lodges, valveless, dangerous venous plexus [Batsons].. 12

13

CONTENTS OF THE VERTEBRAL CANAL

� Spinal cord

� is a cylindrical, grayish-white structure, 42-45 cm in length that begins above the foramen magnum, where it is continuous with the medulla oblongata of the brain.

� It terminates below in the adult at the level of the lower border of the first lumbar vertebra.

� In the young child it is relatively longer and ends at the upper border of the third lumbar vertebra.

14

BLOOD SUPPLY OF THE SPINAL CORD

� The spinal cord receives its

arterial supply from three

small, longitudinally running

arteries-the two posterior

spinal arteries branches of

posterior inferior cerebellar

arteries and the one anterior

spinal artery branch of

Vertebral artery,15

� The veins of the spinal

cord drain into the

internal vertebral

venous plexus

16

Meninges of the spinal cord1. Dura mater

� the most external membrane and is a dense, strong, fibrous sheet that encloses the spinal cord and cauda equina.

� Continuous above through the foramen magnum with the meningeal layer of duracovering the brain.

� Inferiorly, it ends on the filumterminale at the level of the lower border of the second sacral vertebra.

� Epidural space- contains loose areolar tissue and the internal vertebral venous plexus.

17

2. Arachnoid mater

� a delicate impermeable membrane covering the spinal cord and lying between the pia mater internally and the dura mater externally.

� Separated from the dura by the subdural space that contains a thin film of tissue fluid.

� Separated from the pia mater by a wide space, the subarachnoid space, which is filled with cerebrospinal fluid.

� Inferiorly , it ends on the filum terminale.

18

3. Pia mater

� A vascular membrane

that closely covers the

spinal cord.

� Below it fuses with the

filum terminale

� The pia mater is

thickened on either side

between the nerve roots

to form the ligamentum

denticulum, which

passes laterally to be

attached to the dura.

19

LIGAMENTUM DENTICULATUM

� These are the ribbon like

thickened bands of pia

mater,extending

laterally,piercing the arachnoid

and attached to the inner

surface of the duramater

� The first teeth of denticulatum

lies at the level of foramen

magnum

� The last between T12andL1

� The lowest tooth is forked and

the posterior root of the L1 lie

at the outer prong of the fork

� Serve as a guide in cardotomy

20

(anterior view)

dorsal n. root

ventral n. root

denticulate

ligaments

CONUS MEDULLARIS and CAUDA

EQUINA

� The roots of the nerves lumbar, sacral and coccygeal leave through appropriate numbered intervertebral foramen

� They together look like a horse tail-cauda equina

� The terminal end of the spinal cord-conus medullaris.

22

CONUS-MEDULLARIS

� The Terminal end of

the spinal cord-conus

medullaris.

� Adult-L1.

� Children-L3

Conus medullaris and cauda equina

24

EPIDURAL SPACE

� Lies between the spinal duramater and the periosteum and ligaments lining the vertebral canal

� 1.loose areolar connective tissue

� 2.semiliquid fat

� 3.spinal arteries

� 4.the internal vertebral venous plexus.

25

Applied anatomy

� Lumbar epidural anaesthesia

� Between L3 and L4 spine n eedle course through, skin, fat, supraspinous and interspinous ligaments, ligamentum flava, epidural space.

� This space is confirmed by the fact that it is a space with negative pressure

26

CAUDAL EPIDURAL ANAESTHESIA

� The needle is passed

through sacral hiatus

which lies equidistant

from the right and left

posterior superior iliac

spines and enters the

sacral canal

� This space lies below

S2

27

SUBDURAL SPACE

� Is a potential space between the duramaterand the arachnoid, containing thin film of serous fluid.

� Permits movements of dura over the arachnoid

� Continued for a short distance on to the spinal nerve

� Free comunication with the lymph spaces around the nerves

28

Figure 12.29a

Cervical

enlargement

Dura and

arachnoid

mater

Lumbar

enlargementConus

medullarisCauda

equina

Filum

terminale

Cervical

spinal nerves

Lumbar

spinal nerves

Sacral

spinal nerves

Thoracic

spinal nerves

FILUM TERMINALE

� he filum terminale("terminal thread"), is a delicate strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris. It is one of the modifications of piamater.

SUB ARACHNOID SPACE

� IS a wide space

between the pia and

the arachnoid filled

with CSF

� Spinal sub arachnoid

space is wider then the

space around the brain

� Widest below where it

encloses the caudae

30

Applied aspects

� LUMBAR PUNCTURE:

� Done through the

Intervertabral disc

between L3 and L4 for

threuptic and diagnostic

purpose.

� In children-vertabrel

level-L1.

31

VERTABREL SYSTEM OF VEINS.

VERTESBRAL SYSTEM OF VEINS

� The vertebral venous

system –

valveless,complicated

network ,with

longitudinal pattren

� Runs parallel to SVC

andIVC and

anastomoses with

them

34

35

� This network has three intercommunicatiingsub divisions

� 1,the epiduralplexus lies in the vertebral canal outside the durameter

� Consists of 1. postcentral2.pre laminar portion

� This plexus drains the structures in the vertebral canal

� Itself drained at regular intervals by

� Segmental veins-vertebral,posteriorintercostal,lumbar and lateral sacral .

36

� Plexus within the

veretebral bodies-

drains backwards into

the epidural plexus

� Anterolaterally-into

the external vertebral

plexus

37

3. External vertebral venous plexus-

� It consists of anterior vessels lying in front of the vertebral bodies

� Posterior vessels on the back of the vertebral arches and on adjacent muscles- drained by segmental veins

� The sub occipital plexus of veins lying in the sub occipital triangle is a part of external venous plexus

� It receives the occipital veins of the scalp – connected with the transverse sinus by emissary veins and drains into the subclavian veins

38

BATSON’S PLEXUS

39

The azygos system also

communicates with a valveless

venous network known as

BATSON’S PLEXUS. When the

vena cava is partially or totally

occluded, Batson’s plexus

provides an alternate route for

blood return to the heart.

The vessels of Batson’s

plexus may be referred to as

epidural veins

Batson’s plexus

� Communications- valveless vertebral system of veins communicates

1. Above with intracranial venous sinuses

2. Below with the pelvic veins, portal vein and cavalsystem of veins

� The veins are valveless and so the blood can flow in either direction

� An increase in intra thoracic or intra abdominal pressure due to coughing and straining may cause blood to flow either upwards or downwards away from heart

� Such periodic changes in venous pressure are clinically important

40

� There may possible spread of tumours or

infection-eg: cells from pelvic, abdominal

thoracic and breast tumours-venous system-

lodge in the vertebra, spinal cord, skull or the

brain

� Primary sites of tumours causing secondaries in

vertebra are breast, prostate and kidney

� Vertebral caries – tuberculous infection with in

the veretebrae

41

46