Spinal Cord Anatomy Flashcards by Carol Dumond

The spinal cord begins as the brainstem transitions through the ________ and ends at ________ in adults and _______ in children.

Foramen Magnum; L1-L2; L2-L3

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Rootlets -> Dorsal or Ventral Root -> Spinal Nerve (roots come together) -> Dorsal Primary Rami & Ventral Primary Rami

Spinal Cord Formation

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How many spinal cord segments are there total?

31 spinal cord segments

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Cervical Segments:
Thoracic Segments:
Lumbar Segments:
Sacral Segments:
Coccygeal Segments:

8
12
5
5
1

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How many pairs of spinal nerves are there?

31 pairs of spinal nerves

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Sensory root that carries information from the body to the spinal cord for processing.
-Ganglion is found outside the spinal cord

Dorsal Root

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Motor root that carries signals from the CNS out to the body.
-Ganglion is within the spinal cord

Ventral Root

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A group of fibers that comes directly off of the Spinal Nerve, goes to the side of the spinal column and projects into a Sympathetic Chain Ganglion.
-Also called White Rami Communicantes (myelinated)
-Type B Fibers = Motor

Preganglionic Sympathetics

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New fibers initiated from the Sympathetic Chain Ganglion that rejoin the spinal nerve.
-Exist between T1-L2,L3
-Gray Rami Communicantes (Unmyelinated).
-Type C Fibers = Motor

Postganglionic Sympathetics

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The major plexi all come from what?

Ventral Primary Rami

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C1-C4, with a small part of C5 contribution for Phrenic Nerve (diaphragm)

Cervical Plexus

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C5-T1

Brachial Plexus

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L1-S4, with about 50% of the population having a contribution from T12

Lumbosacral Plexus

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S4, S5, and Coccygeal Nerve

Coccygeal Plexus

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How long is the spinal cord?

58-60 cm (23-24 in)

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How long is the vertebral column?

About 2.5 ft in length (about 0.5 foot longer than spinal cord)

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Why is the area below the end of the spinal cord (below L1-L2) good for spinal injections and spinal fluid withdraws?

Because below the spinal cord are dorsal/ventral roots (Cauda Equina) floating in CSF. Floating in a big bag of Dura Mater containing fluid.

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Where does the Conus Medullaris occur?

Between L1-L2

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The Conus Medullaris continues down as a little filament that attaches to the coccyx to hold the spinal cord in place.
-Consists of rope of pia mater and glial cells.
-Runs in the sacral canal, exits via the sacral hiatus, and attaches to coccyx
-Without this, the spinal cord would be flopping around.

Filum Terminale

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A large arachnoid/Dura Mater ending that holds CSF. Forms a cavity.
-Continues down to S2 vertebra where it ends.
-Creates a bag of CSF that contains dorsal/ventral roots (Cauda Equina)

Lumbar Cistern

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Represents a line drawn across one iliac crest to the other. The top of iliac crests on both sides is L4.
-Have the patient bend over to visualize
-Safe spot for placing needle since it’s well below L1-L2.

Tuffier’s Line

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Where are the two enlargements of the spinal cord located?

-Cervical Enlargement exists between C5-T1 for the Brachial Plexus
-Lumbosacral enlargement between L1-S4 for the Lumbosacral Plexus

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Where does the Cauda Equina originate from?

The Lumbosacral enlargement of the spinal cord (L1-S4).

A trilaminar covering that surrounds the spinal cord, and extends out to the spinal nerves.
-When you do a lumbar puncture, you are anesthetizing the dorsal/ventral roots as well.

Dura, Arachnoid, and Pia Mater

Very thin, round layer that goes all the way out to the spinal nerve. -Tightly encases the spinal cord - "Tender Mother" -Can't see the spinal cord unless you strip this off

Pia Mater

Middle layer -Sub____ space is encases between this and Pia Mater. Contains CSF

Arachnoid Mater

Outer layer, fits very loosely on the spinal cord. Extends out over roots as well. - "Tough Mother"

Dura Mater

Modifications of Pia Mater. -Row of teeth coming off of spinal cord -Layer of Pia Mater -Occurs between Dorsal and Ventral Roots -Holds the Dura Mater in place, doesn't let it slide off, go up or down, etc. -Pierces the Arachnoid and attaches underneath it to the dura mater.

Denticulate Ligaments

How many Denticulate Ligaments are there?

21 on either side

Space between the Pia Mater and Arachnoid Mater -Real space; contains CSF -Continuous with the _______ space in the brain. -Intra-thecal

Subarachnoid

A potential space; have to pull layers apart to force it to exist. -Arachnoid sticks/adheres to Dura Mater

Subdural Space

A potential space in the brain, but a real space in the spinal cord. -Contains fat for padding & injury prevention -Has anterior/posterior venous plexi -To be reached, have to go through supraspinous, interspinous ligaments, and Ligamentum Flavum (which offers the most resistance).

Epidural Space

Why when you anesthetize the spinal cord, it is carried out to the spinal nerve. -More bang for your buck -Sensory and motor anesthesia

The spinal cord is encased with Pia Mater and Arachnoid Mater (and Dura Mater?) that are carried out to the spinal nerves. -Also anesthetizes the dorsal/ventral roots coming off of the spinal cord. -Gets sensory & motor anesthesia

Contained in the Epidural Space. -Anterior is more developed than posterior -Anterior > Posterior -Veins anastomose with each other

Anterior/Posterior Venous Plexi

Vein that drains the vertebral bodies. -Also picks up drainage from the anterior/posterior venous plexi -Runs over the body of the vertebrae

Basil Vertebral Vein

Looks like a butterfly. -Neuron cell bodies -Some unmyelinated fibers -Contains a Dorsal and Ventral Column -Lateral Column that is just a little pocket pushing out that contains cells. Kind of off of the Ventral Column

Gray Matter

Consists of myelinated axons -Contains a Dorsal, Ventral, and Lateral Column

White Matter

Near the commissure connecting the butterfly wings. A holdover remnant of the neural tube -Very tiny opening

Central Canal

The point where the two gray matter areas on either side connect across the midline of the butterfly

Gray Commissure

Pocket pushing out of the Ventral Gray Horn -Contains Cell bodies that originate preganglionic fibers of the SNS (T1-L2, L3) -Contains Cell bodies that originate preganglionic fibers of the PARASYMPATHETIC (S2-S4) and supplies innervation to the pelvic viscera

Lateral Gray Horn

A Cleft that runs deep in white matter. Divides the spinal cord into symmetrical halves (R and L)

Anterior Median Fissure

Divides the spinal cord into symmetrical halves (R and L) -Not as deep

Posterior Median Sulcus

Occur where Dorsal Rootlets enter the spinal cord -2 of them

Dorsolateral Sulci

Occur where Ventral Rootlets exit the spinal cord -2 of them

Ventrolateral Sulci

Bisect the dorsal white columns -Split white matter into lateral and medial halves -Start at about T8 and go up to C1. Don't have any in the lower spinal cord

Dorsal Intermediate Sulci

Portion of white matter that carries information from the upper half of the body. -Proprioception & tactile senses

Lateral Portions of White Matter (created by Dorsal Intermediate Sulci)

Portion of white matter in between the two dorsal intermediate sulci. -Carries information from the lower half of the body. -Proprioception & tactile senses

Medial Portion of White Matter (created by the Dorsal Intermediate Sulci)

Vertebral Artery goes upwards, passes through C1, and goes medially, then goes through the Foramen Magnum. Gives off tiny arteries called the _________ (left and right). Very small artery, like spiderwebs -DS Artery is accompanied by Feeder Arteries (Segmental Arteries) that boost arterial flow to the spinal cord. -Supplies the Dorsal 1/3 of the spinal cord

Dorsal Spinal Artery

Arteries at the conus medullaris that are mixing in with the nerves of the Cauda Equina. -Derived from Lateral Sacral Arteries

Cauda Equina Arteries

Lesion of injury here will involve these areas: -Tactile sense, 2 point discrimination, stereognosis, etc. -Dorsal White Column Injury

Posterior 1/3 of the spinal cord (Supplied by Dorsal Spinal Arteries, Feeder Arteries, and Cauda Equina Arteries)

Lesion here will cause: -Loss of motor control of upper & lower limbs -Loss of ability to act with cerebellum -Loss of pain & temperature

Anterior 2/3 of spinal cord (Supplied by the Ventral Spinal Artery, Feeder Arteries, and the Cauda Equina Arteries)

Vertebral Artery comes off of the Subclavian, goes upward, passes through C1, and goes medially, then goes through the Foramen Magnum. Gives off a BIG artery called the ______ Spinal Artery -Feeder/segmental arteries assist it, but not as many are needed because this is a bigger artery and carries more blood -Goes down to Cauda Equina Arteries and anastomoses with the Lateral Sacral Arteries -Lies superficially within the Anterior Median Fissure.

Ventral Spinal Artery

A feeder artery that is larger than the others -Gives good blood supply to the rest of the spinal cord -Located most of the time off of the left side -Generally at about T8-T12 spinal cord segments -VERY important in preventing lack of O2 to spinal cord from that point down. -Risk of severing it during surgery, especially during Abdominal Aneurysm repair -Injury to this causes loss of blood flow and partial paralysis -Anastomoses with the Anterior (Ventral) Spinal Artery

Anterior Medullary Artery of Adamkiewicz

Segmental Arteries that come off of the Posterior Intercostal Arteries. -Bifurcates into one small artery that goes over the ventral root, and one that goes over the dorsal root -Goes over the roots, so called Radicular Arteries (Radicular = Root) -Divides into anterior/posterior -Anastomoses with other arteries on the spinal cord to form a continuous loop of blood

Feeder Arteries

Run in Epidural Space -Anterior Internal: Runs up & down posterior aspect of vertebral bodies. Accepts drainage from vertebral bodies and from spinal cord to be recirculated -Posterior Internal: Smaller than anterior. -Anterior External -Posterior External Externals join with Internals by the Vertebral Anastomotic Veins

Venous Plexi

Cancer of nervous system or of Prostate will metastasize in these veins and spread. -Has a thick sheet of fascia that protects, but can eventually be broken down

Venous Plexi