dpt anatomy - back 2

suboccipital triangle is located

• deep to semispinalis capitis

• between occipital bone and posterior aspects of C1 and C2

the spinal cord is a continuation of

the medulla oblongata (part of the brainstem) that extends from the foramen magnum at the base of the skull

where does spinal cord extend to and what does it terminate as

• extends down to L1/L2 vertebral level

• terminates as conus medullaris

what is cauda equina

a collection of dorsal and ventral roots that will from spinal nerves but that need to exit through intervertebral foramina that are below the vertebral level of the conus medullaris

how many cervical, thoracic, lumbar, sacral, and coccygeal segments does the spinal cord contain

• 8 cervical

• 12 thoracic

• 5 lumbar

• 5 sacral

• 1 coccygeal

each spinal cord segment gives rise

dorsal and ventral roots that join together to form a spinal nerve

what is each spinal nerve responsible for

contributing to the innervation of a specific myotome and dermatome

the spinal cord is covered by

3 layers of meninges

• dura mater

• arachnoid mater

• pia mater

dura mater

outer tough collagenous tissue that encloses the spinal cord and the cauda equina

dura mater is continuous with ___ and extends to ___

continuous with dura of the brain at the foramen magnum and extends as a tube down to S2 (we call this the end of the dural sac)

dural sleeves

extends out around spinal nerves as they exit, then dura blends with epineurium of nerve

epidural space

space between the dura and the bony interior of the vertebral canal

subdural space

space between the dura mater and the arachnoid layer

where is the arachnoid mater located

lines the inside of the dural sac and extends as a web through subarachnoid space to attach to the pia mater

what is the subarachnoid space and what does it contain

• space between arachnoid and pia mater

• contains cerebrospinal fluid

lumbar cistern

subarachnoid space between L2-S2

• good place to get fluid samples (safest to get fluid from L4 and below during spinal tap)

• contains cauda equina and filum terminale internum

• 

pia mater

• bound to the surface of the spinal cord and nerve roots

pia mater continues as

filum terminale internum (FTI) inferior to the conus medullaris

• FTI is surrounded by cauda equina until it reaches the end of dural sac at S2

denticulate ligaments

lateral projections of the pia mater that form triangular shaped ligaments that extend from the spinal cord to the internal surface of the dura mater

function of denticulate ligaments

stabilizing

how many pairs of denticulate ligaments are there

21

where are dorsal and ventral roots in relation to denticulate ligament

• dorsal roots are on posterior sides of denticulate ligaments

• ventral roots are on anterior side of denticulate ligaments

what happens to the filum terminale internum at the end of dural sac

FTI passes through (and gains a layer of dura) and continues as filum terminale externum (FTE)

• FTE continues inferiorly and attaches to coccyx as the coccygeal ligament

enlargement of spinal cord are in

cervical and lumbar

• bc there are so many axons that need to exit in the lower cervical and lumbar region

why is cervical and lumbar enlargement clinically important

the enlargement might be more susceptible to having compression at the spinal nerves

where do cervical nerves exit?

above their corresponding segment

i.e. C2 spinal nerve exits above C2 (through the intervertebral foramen between C1 and C2)

C8 exits BELOW C7 (between C7 and T1)

where do thoracic, lumbar, sacral, and coccygeal spinal nerves exit?

BELOW their corresponding spinal vertebra

i.e. T 1 spinal nerve exits below T1 (through intervertebral foramen between T1 and T2)

why are lumbar and sacral roots the longest

because they are the farthest from the intervertebral foramina where they will exit

how does herniated disc affect the vertebra

• when small, an HNP usually affects spinal nerve whose number corresponds to the number of the vertebra below the disc

• i.e. HNP at L5/S1 (most common) will usually affect S1

spinal block (anesthesia)

inject into subarachnoid space for child birth

• inferior to waist level

epidural block

inject into epidural space

• doesn’t go into SC or CSF

• can target a region

• common during childbirth as they can target L3/L4 level (anesthesia for uterus and cervix) but doesn’t affect lower limbs as much

caudal epidural anesthesia

• acts on S2-Co1 spinal nerves

• injected into sacral canal via sacral hiatus

• pudendal nerve block - popular for childbirth - bathes S2-4 spinal nerves so can’t feel birth canal, pelvic floor, but usually doersn’t affect lower limbs so patient can participate