Back Flashcards
Vertebral arch consists of:
- 2 pedicles that attach to the body (walls of the house)
- 2 laminae that unite to form the spinous process (roof)
How many vertebrae are in the vertebral column?
- 33 but only 24 individual: 7 cervical, 12 thoracic, 5 lumbar
- five fused sacral = sacrum
- four coccygeal = cocyx
Spina Bifida:
- when laminae fail to fuse to form the spinous process
- most common in the lower lumbar or sacral vertebrae
Types of Spina Bifida:
- occulta: spinous processes fail to form at lumbar or sacral level. Asymptomatic - may show tuft of skin over defect
- cystica: cyst protrudes from the defect at the vertebral arch. Diagnosed in utero due to elevated alpha-fetoprotein. May result in hydrocephalus and neurological defects.
- Cystic with Meningocele: cyst lined by dura/arahnoid and contains cerebrospinal fluid
- cystica with meningomyelocele: lumbosacral spinal cord displaced into the cyst. Lumbosacral spinal nerves stretch. Results in bladder, bowel, and lower limb weakness.
- Myeloschisis/rachischisis: caudal end of the neural tube fails to close in the dorsal midline and is exposed on the surface of the back
Transverse process:
formed by the costal processes and projects between the pedicle and the lamina
Four curvatures in adults:
- cervical and lumbar: secondary curves directed anteriorly
- thoracic and sacral: primary curves directed posteriorly
kyphosis:
- abnormal curvature of the spine
- an abnormal increase in the posterior curvature of the spine
- most common is postural kyphosis
- can also be caused by anterior wedge-shaped thoracic vertebrae OR resorption of the anterior parts of the thoracic vertebral bodies (from osteoporosis)
lordosis:
- abnormal curvature of the spine
- abnormal increase in the anterior curvature of the spine that may be caused by a weakening of the anterior abnormal wall musculature (due to weight gain)
scoliosis:
- abnormal lateral curvature that may be caused by:
1) an absent half of a vertebra or
2) a wedge-shaped vertebra OR
3) by an asymmetric weakness of back musculature
Individual vertebrate articulate at:
- facet joints
- through intervertebral disks
- supported by ligaments
Zygapophysel (facet) joints:
- formed between the facets of superior/inferior processes at the junction of each pedicle and lamina
- permit gliding motions
- deep back muscles act on facet joints
intervertebral disk consists of:
fibrocartilaginous annulus fibrosus that surrounds a nucleus pulposus (postnatal remnant of the fetal notochord)
intervertebral disk functions:
- movement of the adjacent bodies produce compression and tension in different parts of the disk
- the disks function to absorb shock and distribute weight over the entire surface of the body
anterior longitudinal ligament:
- covers the anterolateral parts of the body
- functions to limit vertebral extension
posterior longitudinal ligament:
- covers the posterior part (inside the vertebral foramen) of the disk
- functions to limit vertebral flexion
- narrower and weaker than anterior
elastic ligamentum flavum:
- extends between the laminae of adjacent vertebrae
- like posterior they limit vertebral flexion
- maintain normal vertebral curvatures
intervertebral foramina:
- separate individual vertebra
- transmit dorsal and ventral roots of spinal nerves into and out of the vertebral canal
- bounded by the pedicles of adjacent vertebrae, posteriorly by facet joints and anteriorly by bodies/intervertebral disks
vertebral canal:
- formed by all of the individual vertebral foramina/ligaments and disks that interconnect them
- consists of meninges, spinal cord, and the roots of spinal nerves
epidural space:
- outside the dural layer of the meninges
- contains fat and the internal venous plexus
internal venous plexus:
- connects veins that drain the thorax, abdomen, and pelvis with the dural venous sinuses of the cranial cavity
- provides a route for metastasis of neoplasms of the prostate, uterus, and rectum to the cranial cavity
dura mater:
- continuous with the meningeal dura of the cranial cavity
- ends at the level of S2
- lateral extensions of the dural sac contain the roots of spinal nerves
subdural space:
-potential space between the dura and the arachnoid mater
arachnoid mater:
-extends to the level of S2 and pressed against the dura by the pressure of CSF
subarachnoid space:
contains CSF
- CSF is secreted into ventricles of the brain then circulates through the subarachnoid space and returns to the venous system
- CSF has normal pressure of 100 mmH2O
CSF functions:
- cushions the brain & spinal cord
- absorbs waste products
- transports hormones
- it is a clear fluid containing few cells, low protein content, and lower glucose concentration than serum
pia mater:
- covers the spinal cord and roots of the spinal nerves
- denticulate ligaments: lateral extensions of pia that anchor the spinal cord to the dura
- filum teminale: consists of pia that extends from the inferior end of the cord at level L2 and joins the dura/arachnoid to end in the sacral canal (S2)
intervertebral disks and aging:
- as you age you lose annulus fibrosus as the nucleus pulposus invades
- lose some cushion
- nucleus pulposus becomes more brittle and vulnerable to tears
Spinal Cord location:
- occupies superior 2/3 of the vertebral canal
- ends inferiorly at L2
- conus medullaris: tapered inferior end of the spinal cord that contains the sacral and coccygeal cord segments (at L2)
Spinal nerves exit:
-through the intervertebral foramina, sacral foramina, or sacral hiatus
Cervical nerves exit:
-first seven exit superior to the cervical vertebra for which they are named
(IE) CN 4 exits between C3 and 4
**After T1 they exit inferiorly
How does the 8th cervical nerve exit:
-through the intervertebral foramen between C7 and T1
because there are 8 cervical nerves but only 7 cervical vertebrae
cauda equina:
formed by dorsal and ventral roots of lumbar and sacral spinal nerves that extend inferior to the end of the spinal cord at L2
Lumbar puncture:
- procedure used to sample CSF (cerebral spinal fluid) or to introduce anesthetic agents into the subarachoid space
- typically performed between the L4 and L5 (well below inferior end of spinal cord)
Meninges
- thin membranes that cover the spinal cord and brain
- pia (closest to the spinal cord) -> > subarachnoid space containing CSF -> arachnoid -> dura
in a midline lumbar puncture a needle will transverse:
- skin
- superficial and deep fascia
- supraspinous and interspinous ligaments
- intralaminar space
- epidural space
- dura
- arachnoid
*if it were done off of the midline it would transverse a ligamentum flavum instead of supraspinous/interspinous/intralaminar space
Radiculopathies:
What is it:
-compression of the roots of spinal nerves in the intervertebral foramina or vertebral canal
Symptoms:
- pain and paresthesia (tingling/numbness) in dermatomes supplied by the root
- weakness of skeletal muscle
Causes:
-osteoarthritis, spondylitis, spondylosis, herniated disk
Osteoarthritis:
inflammation that results in additional bone growth by osteophytes at the facet of bone joints
Spondylitis:
- inflammation that results in additional bone growth at the MARGINS of the vertebral bodies
- anterior longitudinal ligament and sacroiliac joint may undergo calcification
SYMPTOMS:
- ankylosis (joint stiffening)
- bamboo spine (Marie-Strumpell disease)
(“ITIS” = growth)
Spondylosis:
- degenerative changes in intervertebral disks
- usually combined with osteoarthritis at the margins of the vertebral bodies
(“SIS” = degeneration)
Cervical vertebrae characteristics:
- small bodies
- short spinous processes with bifid tips
- transverse processes that transmit vertebral arteries
- they have facet joints of C3-C7 vertebra that are oriented at a 45 degree angle relative to the transverse plane (allows flexion, extension, lateral bending, and rotation)
- uncinate processes on the bodies of C3-C7 form uncovertebral synovial joints with the vertebral bodies superior to them
Whiplash:
-caused by the strong extension then flexion of cervical vertebrae which results in an anterior dislocation of the facet joints
Osteoarthritic changes in uncovertebral synovial joints:
result in compression of the roots of C3-C7 cervical spinal nerves
Atlas:
- C1
- posterior arch and anterior arch (no body or spinous process)
- NO intervertebral disk between C1 and C2
- superior articular processes of the atlas articulate with the occipital condyles of the skull
- these facet joints permit flexion (tilt head forward - decrease angle of neck) and extension (tilt head back back - increase angle of neck)
- YES joint
Axis:
- dens articulates with the anterior arch of the atlas
- no (pivot) joint that permits rotation of the atlas and skull
Transverse ligament of the atlas
- holds the dens of the axis in place
- rupture causes dislocation of the atlantoaxial joint and displacement of the dens posteriorly into the cervical spinal cord
- compression of the ventrolateral part of the cervical spinal cord by the dens may result in quadriplegia
Alar ligaments:
- attach the dens to the margins of the foramen magnum
- rupture causes excessive rotation of the skull
C7 vertebra
- vertebra prominens
- long spinous process
- small transverse foramina that do not transmit vertebral arteries
Herniated disk (nucelus pulposus)
- occurs when the nucleus pulposus protrudes at the posterolateral part of an annulus fibrosus
- results in compression of spinal roots most commonly in the lower cervical and lower lumbar region
- compressed roots are usually from the inferior spinal nerve (IE: herniations at C5-6 disk compress C6 roots)
Herniated nucleus pulposus at cervical level:
- most commonly at the disk between C6 and C7 (C7 spinal nerve compression)
- less commonly between C7 and T1 (compresses C8 spinal nerve)
Compression of C7 spinal nerve:
- results in referred pain in the neck and shoulder
- pain and paresthesias in index/middle fingers
- diminished triceps reflex
- weakness in extension of the forearm at the elbow
- weakness in extension of the wrist and fingers (posterior forearm muscles)
Compression of C8 spinal nerves:
- results in pain in the neck and shoulder
- pain and parethesias of ring and little finger
- weakness in hypothenar and interosseous muscles of the hand
Cervical Rib
- may arise from the costal process of C7
- may compress the T1 spinal nerve and subclavian artery as they course superior to the cervical rib instead of superior to the first thoracic rib
SYMPTOMS:
- diminished radial pulse
- pain and paresthesias in medial forearm
- may also present similar to Horner’s Syndrome
Thoracic vertebrae characteristics:
- heart shaped bodies
- long, obliquely oriented spinous processes
- costal facets on the bodies
- transverse processes
- facet joints oriented at 60 degree angle relative to the transverse plane which allows lateral bending and rotation
- flexion and extension are limited by fixation provided by ribs
Lumbar vertebrae characteristics:
- kidney shaped bodies
- short, horizontally oriented spinous processes
- long transverse processes
- facet joints are oriented horizontally to the transverse plane allowing flexion and extension and lateral bending
- rotation limited
Isthmus (pars) interarticularis:
- connected the superior and inferior articular processes of the lumbar vertebrae
- Scottie Dog (it is the neck)
Spondylolysis:
- defect/fracture of the isthmus without anterior displacement of the vertebrae
- Scottish dog wear a collar at site of fracture
Spondylolisthesis:
- unilateral or bilateral defect or fracture of the isthmus accompanied by anterior displacement of the vertebral body
- Head of the Scottish Dog (transverse process) separated from body
- most commonly between L5 and sacrum
- may stretch the roots of lumbosacral spinal nerves in the cauda equina
SYMPTOMS:
-lower back pain that radiates into both lower limbs and muscle weakness in legs
Spinal stenosis:
- narrowing of the vertebral canal
- could be caused by spondolylosis in which degenerative changes occur in the L4 and L5 intervertebral disks
- may also be caused by osteoarthritis at the facet joints at L4 and L5
Herniated disk at lumbar level:
- most commonly between L4 and L5 (compress L5 nerve roots) or L5 and S1 (compress S1 nerve roots)
- small herniations compress the nerve roots of spinal nerves exiting through the intervertebral foramina below the affected disk
Compression of L5 or S1 spinal nerve roots:
- may result in sciatica (pain that radiates from the back into the thigh, leg, and foot)
- compression of L5: pain and paresthesias in the posterior thigh, anterolateral leg, and dorsum of the foot.
- there may be weakness in extension of the great toe (extensor hallucis longus) and weakness in dorsiflexion (tibialis anterior)
Compression of S1 spinal nerve roots:
- result in pain and paresthesias in the posterolateral leg, heel, and lateral side of the foot
- may be weakness in flexion of the leg at the knee (hamstrings), weakness in plantar flexion (gastrocnius and soleus), and diminished Achilles tendon reflex
Sacrum:
- composed of 5 fused sacral vertebrae
- superior aspect bears and transmits weight to the pelvic girdle
- contains median crest (fused sacral spinous processes) and intermediate crests (fused articular processes)
- promontory forms the ventral surface, boundary of the pelvic inlet (important in obstetrics)
- articulates at the sacroiliac joints (formed by the lateral surfaces of the superior part of the sacrum and medial surface of the ilium)
- four pairs of dorsal sacral foramina and four pairs of ventral sacral foramina that transmit the dorsal and ventral rami of S1-S4
- contains the sacral canal which ends at the sacral hiatus in the dorsal midline and contains the roots of the S1 coccygeal spinal nerves
- the sacral hiatus transmits S5 and coccygeal spinal nerves
Caudal Block
- epidural block
- performed by administering anesthetic through the sacral hiatus which diffuses through the meninges anesthetizes the roots of the sacral and coccygeal spinal nerves in the cauda equina
Coccyx
- formed by 3-5 fused coccygeal vertebrae
- it is an attachment site for the gluteus maximus and anococcygeal ligament (attachment site for muscles of the pelvic diaphragm)
Superficial muscles of the back:
- attached to the pelvic girdle and act on the upper extremity
- trapezius, latissimus dorsi, rhomboid major, rhomboid minor, and levator scapulae
- innervated by ventral rami of spinal nerves through branches of the brachial plexus (except for trapezius which is supplied by CN XI accessory nerve)
Intermediate muscles of the back:
- attach to the ribs and act as accessory muscles of respiration
- serratus posterior inferior and 12 pairs of levator costarum muscles
- innervated by ventral rami of spinal nerves
Deep (intrinsic) muscles of the back:
- attach mainly to transverse and spinous processes of vertebrae and act on the vertebral column at the intervertebral joints
- erector spinae (includes 3 parallel muscles: iliocostalis, longissimus, and spinalis (medial)
- splenius capitis and splenius cervicis (lie superficial to components of the erector spinae in the neck) and act unilaterally to produce lateral bending of the cervical vertebrae
- transversospinalis muscles: 3 muscle groups that lie deep to the erector spinae
- muscles of suboccipital triangle contribute to extension at the atlantooccipital joins and rotation at the atlantoaxial joints
- innervated by dorsal rami of spinal nerves
Function of the erector spinae:
- act bilaterally to extend the vertebral column at intervertebral joints
- act unilaterally to produce lateral bending of the vertebral column at intervertebral joints
splenius capitis
extends the head
splenius cervicis
rotates the head
transversospinalis muscles
-superficial to deep:
semispinalis -> multifidus -> rotatores
- acting bilaterally they extend the vertebral column
- unilaterally they produce rotation of the vertebral column
