4. Deep back and Suboccipital Triangle

Lecture 4 - Halliday

vertebral column review

33 vertebrae - 24 movable

provides posture, supports body weight, locomotion, and spinal cord protection

vertebral column curvatures

primary curvature - concave anteriorly (kyphosis - thoracic and sacral; fetal)

secondary curvature - concave posteriorly (lordosis - cervical and lumbar; weight bearing)

cervical vertebrae - typical and atypical

atypical: atlas (C1) and axis (C2). sometimes vertebral prominens C7) is included

typical: C3-C7

characteristics of typical vertebra

body: cylindrical mass of bone on the anterior aspect, primary weight-bearing structure, adjacent vertebral bodies are connected by intervertebral discs

vertebral arch: surrounds the vertebral foramen

• pedicles (2) attach to the body and form the lateral walls of the arch

• laminae (2) flat plates that form the posterior (dorsal) wall of the arch

• spinous process (1) projects posteriorly from the junction of the laminae

Projections: 7 total per vertebrae

• spinous process posterior projection

• 2 transverse processes - arise from the junction of pedicles and laminae

• 2 superior articular processes - articulate with the vertebra above

• 2 inferior articular processes - articulate with the vertebra below

• mammillary processes (lumbar only) - tubercles on the superior articular processes. attachment point of multifidus muscle

foramen:

• vertebral foramen and vertebral canal- formed by the body, pedicles and laminae, collectively create the vertebral canal when vertebrae are articulated, house the spinal cord and meninges

• intervertebral foramina - located between adjacent vertebrae (between superior and inferior pedicles), transmit segmental spinal nerves

• transverse foramina (cervical vertebrae only) - located within the transverse process, transmit the vertebral artery (except C7) and accompanying veins

(7) cervical vertebra regional characteristics

most movable. found in the neck. transverse foramina present. transmit vertebral vessels

C2-C6 vertebra regional characteristics

bifid spinous processes

C7 vertebra regional characteristics

vertebra prominens

long prominent spinous process (not bifid)

C1 (atlas) vertebra regional characteristics

no body and no spinous process. consists of anterior and posterior arches. superior articular facets articulate with occipital condyles

support the head

atlanto-occipital joint - synovial joint. flexion and extension (yes motion)

C2 (axis) vertebra regional characteristics

contains the dens (odontoid process). projects superiorly, dens articulates with the anterior arch of C1, serves as a pivot for rotation

atlanto-axial joint allows lateral rotation (“no” movement)

ligamentous support of the dens: transverse ligament. alar ligaments, superior and inferior longitudinal bands. these ligaments prevent posterior displacement of the dens toward the spinal cord

relationship of vertebral arteries and cervical vertebrae

vertebral arteries arise in neck. pass superiorly through transverse foramen of cervical vertebrae (except C7). branches supply spinal cord. medulla, cerebellum. join to form basilar artery in the cranium

intervertebral foramen transmit spinal nerves.

transverse foramen transmit vertebral arteries

Thoracic vertebrae characteristics

thicker body than cervical

long spinous process (T1-T10 project inferiorly)

costal facets for rib attachment

superior and inferior articular facets (oriented more vertically)

T9 is at same axial plane as xiphoid process

Lumbar vertebrae characteristics

typically short with the thickest body. processes are short and thick

no costal facets

have mammillary and accessory processes for muscle attachments

sacrum characteristics

superior L5 articulation. inferior articulation with coccyx. iliac bone articulation laterally

transmits weight to lower limbs

sacral crest is missing 5th spinout process

sacral canal is a continuation of vert. canal. contains cauda equina

sacral hiatus is formed by lack of fusion of S5 laminae with sacral cornu on each side

coccyx vertebrae characteristics

typically 4 fused vertebrae

site of muscle attachment

vertebral processes joints

zygapophyseal (synovial, joint capsule, ligaments)

vertebral bodies joints

intervertebral (IV) discs, ligaments, sumphyses

annulus fibrosis

rings of fibrocartilage. fibers attach to epiphysial rim of adjacent vertebran

nucleus pulposus

semi-fluid gel

withstands compressive forces

remnant of notochord (embryo)

herniation (of a disc)

stress or aging can lead to a loss of integrity of the annulus fibrosis

most herniations are posterolateral (annulus fibrosis is thinner posteriorly. posterior longitudinal ligament is not very wide)

pain radiating down the leg and muscle weakness

herniation of the disc below L4 with impinge the L5 spinal root

ligamentum flavum

binds lamina of adjacent vertebra and stabilize joints of the arches

interspinous and supraspinous ligaments

connect spinous process

intertransversarii ligament

connects transverse processes

anterior longitudinal ligament

limites extension and prevents hyperextension

longitudinal ligaments stabilize joints of vertebral bodies

posterior longitudinal ligament

limits excessive flexion and prevents hyperflexion

longitudinal ligaments stabilize joints of vertebral bodies

in vertebral canal

atlanto-occipital joint

craniovertebral joint

articulation with occiput

permits flexion/extension

antlanto-axial joint

craniovertebral joint

articulation with C1 (3)

permits rotation of head (side to side)

cruciform ligament

cross-shaped ligament at the craniovertebral junction

stabilizes atlanto-axial joint (C1-C2)

includes a strong transverse band that secures the dens and vertical bands connection the body of C2 to the occipital bone

transverse ligament of the atlas, superior longitudinal band, inferior longitudinal bands

arteries of the vertebrae

arise from branches of regional arteries

divide into anterior and posterior branches

posterior branch gives off spinal branches

veins of the vertebrae

internal (and external) vertebral plexus that connect to segmental veins and inferior vena cava

both anterior and posterior plexuses that lack valves

these provide a route for cancer metastasis to the vertebral column

what is the most common site for bony metastases

the vertebral column due to the veinous plexuses

dorsal horn of spinal cord

receives sensory (afferent) input

ventral horn of spinal cord

contains motor neurons (efferent output to skeletal muscle)

lateral horn of spinal cord

present in thoracic and upper lumbar regions

contains autonomic (sympathetic) neurons

dorsal root

carries sensory fibers into the spinal cord

dorsal root ganglion (DRG)

contains cell bodies of sensory neurons

ventral root

carries motor fibers out of the spinal cord

mixed spinal nerve

formed by the union of dorsal and ventral roots

contains both sensory and motor fibers

dorsal ramus

supplies intrinsic back muscles and skin of the back

ventral ramus

supplies the anterolateral body wall and limbs

rami communicans

connect spinal nerves to the sympathetic trunk

regional differences of spinal cord

there is variation in grey matter depending on function

EX: cervical and lumbar enlargements for limb innervation

epidural space

contains fat and the vertebral venous plexus

dura mater

tough outer covering (durable)

dural sac ends at S2

subdural space

potential space between dura and arachnoid

arachnoid mater

thin, web-like membrane, connected to pia via trabeculae

subarachnoid space

contains CSF

extends to S2

cushions and supports the spinal cord

pia mater

adheres directly to the spinal cord

dentate ligaments

lateral extensions of pia mater that anchor the spinal cord to the dura

filum terminale

an extension of the pia mater that spans from the conus medullaris to the coccyx

anchors the spinal cord inferiorly

cerebrospinal fluid (CSF)

located in the subarachnoid space and central canal of spinal cord

cushions and supports the spinal cord; helps maintain a stable chemical environment

blood supply to the spinal cord

contributions from vertebral, ascending cervical, posterior intercostal, lumbar and sacral arteries

one anterior spinal artery, two posterior spinal arteries, reinforced by segmental vessels

drains into superior vena cava, azygos system, and inferior vena cava

intrinsic (deep) back muscles function

postural

movement of the spine

thoracolumbar fascia

deep fascia of the back

invests intrinsic back muscles

splenius muscle proximal attachment

nuchal ligament and spinous processes C7-T6

splenius distal attachment

capitus: mastoid process and lateral superior nuchal line

cervicis: transverse processes of cervical vertebrae (C1-C4)

Splenius actions

unilateral: lateral flexion and rotation to same side

bilateral: neck and head extension

erector spinal muscles

extensor of the vertebral column (bilateral)

lateral flexion (unilateral)

divided into 3 columns: iliocostalis, longissimus, and spinalis

innervated by the dorsal rami of spinal n

transversospinalis group of muscles

deepest layer of back

layers: semispinalis, multifidus, rotatores

gutter between transverse and spinous processes

semispinalis action

extends head and vertebral column (cervical and thoracic)

rotate to contralateral side

multifidus action

stabilizes vertebrae during local movements

rotatores action

stabilizes vertebrae and assists with local extension and rotation of vertebral column

splenius group

superficial layer of deep back muscles

erector spinae group

primary back extensors

transversospinalis group

stabilization and fine control

innervation of true back muscles

dorsal primary rami

motor - intrinsic back muscles

motor- suboccipital muscles

sensory - 2” vertical strip of skin on both sides of midline of back

suboccipital region

area defined by short muscles that move the occiput

boundaries of suboccipital region

3 suboccipital muscles

roof: semispinalis capitis

floor: posterior arch of atlas, atlanto-occipital membrane

3 muscles of suboccipital triangle

rectus capitis posterior major

obliquus capitis superior

obliquus capitis inferior

suboccipital muscles action

involved in extension and rotation of the head

suboccipital muscles attachments

span from C1 or C2 to the occipital bone

(except obliquus capitis inferior)

blood supply to the suboccipital region

muscular branches of the vertebral artery and branches of the occipital artery supply these muscles