L/S Anatomy Flashcards
describe the body of a typical lumbar vertebrae
- weight-bearing component of structure
- “kidney shaped”
- shell of cortical bone, inner cancellous bone
- ring apophysis: ring on periphery of caudal and cranial surfaces
describe typical lumbar pedicles
- short (stout) w/very thick walls
- transmit force from posterior components to vertebral bodies
describe typical lumbar transverse processes
- project posteriolaterally
- mammillary processes on superior articular process
describe the orientation of typical lumbar spinous process
nearly horizontal
what is the function of lamina?
protect neural structures
transmit forces from articular and spinous processes
where is the pars interarticularis and what is it’s function?
- between S/I articular processes
- oblique from lateral border of lamina to upper border
- transmits forces from horizontal pedicle to vertically oriented lamina
*subject to frx
describe foramen in the lumbar spine
- Spinal
- triangular
- larger than T/S but smaller than C/S
- L1 contains conus medullaris
- L2-5 contain cauda equina and spinal meninges
- Intervertebral
- superior notches are shallow
- inferior are deep
list the ligaments at the lumbar spine
- posterior longitudinal
- anterior longitudinal
- Interspinous
- Supraspinous
- Ligamentum flava
- Iliolumbar ligament
describe the posterior longitudinal ligament
blends w/IV discs
spans from posterior body of C2 to sacrum
describe the anterior longitudinal ligament
thick and pearly
mostly attaches to margins of anterior vertebral bodies
describe the interspinous ligament
attaches superior to inferior SP
paired-filled w/fat
likely proprioceptive in nature
describe the supraspinous ligament
attaches to tips of spinous processes
less common in lower lumbar region
describe the ligamentum flava
attach adjacent lamina
thick, yellow, elastic
checks flexion motion
medial edge fuses w/contralateral ligament (closes vertebral canal)
describe the Iliolumbar ligament
spans from transverse process of L5 to anteriomedial surface of ilium
prevents anterior slipping of L5 on sacrum
resists motions of rotation, flexion, and lateral flexion
List musculature involved with the lumbar spine
- Back muscles
- erector spinae
- multifidus
- interspinales
- intertransversarii
- QL
- Abdominal muscles
- TrA
- Internal oblique
- External oblique
- Psoas major
what is the role of the erector spinae?
what is their innervation?
- group of muscles important for stabilization of curvature
- compressive loads
- innervation: spinal nerves
- medial branch of posterior ramus
what is the largest and most medial of the lumbar muscles?
Multifidus
describe the multifidi
- spinotransverse group
- several fasicles w/varied origin/insertion
- stabilizer against shear during rotation
- eccentrically control flexion of vertebrae inter-segmentally when oblique abdominal muscles rotate the spine
how do multifidi impact zygophyseal joints?
they insert onto zygophyseal joint capsules
they pull the capsules out of the way during extension or during motions when the joints are closing down
what is the origin and insertion of the external oblique?
- originates lateral ribs 5-12
- attaches to:
- inguinal ligament
- linea alba
- ASIS
- iliac crest
- pubic tubercle
what is the action/role of the external oblique?
- Bilateral activation
- vertebral column flexor
- posterior rotation of pelvis
- Unilateral activation
- trunk lateral flexors
what is the origin and attachments of the internal oblique?
- attaches to:
- inguinal ligament
- thoracolumbar fascia
- iliac crest
- pubic crest
- TrA
- costal cartilage of ribs 7-9
what is the role/actions of the internal oblique?
- assists w/postural control during static and dynamic activities
- bilateral activation
- vertebral column flexor
- respiration
- unilateral activation
- trunk rotator
what is the origin and attachments of the TrA?
- Origins:
- inguinal ligament (lateral third)
- anterior 2/3 iliac crest (inner lip)
- thoracolumbar fascia
- lower (6) costal cartilages (along w/diaphragm)
- Upper and middle fibers run transversely around trunk
- blend w/fascia surrounding rectus abdominis
- Lower fibers insert on pubic crest w/internal oblique
what is the role/actions of the TrA?
- lumbar and SIJ stabilizer
- anticipatory activation prior to movement/perturbation
what is the origin and attachment of the QL?
what is it’s innervation?
- Origin → iliac crest and TP of spine
- Insertion → 12th rib and spine (TP of lumbar vertebrae and lateral body of T12)
- Innervated by ventral rami T12-L2
what is the origin and insertion of the psoas major?
what is it’s innervation?
- Origin → TP of lumbar vertebrae, T12-L5 bodies and IV discs
- Insertion → tip of lesser trochanter
- Innervated by ventral rami L1-L2
what is the role of psoas major?
- lumbar stabilizer
- compressive loading on lumbar spine
- lateral flexion moment on spine w/unilateral activation
- important hip flexor
what are the components of IV discs?
- nucleous pulposus
- annulus fibrosis
- vertebral endplates
*there is no clear boundary between nucleus and annulus
describe the nucleus of IV discs
- semifluid, mucoid material
- cartilage cells and irregularly arranged collagen fibers in semifluid ground matrix
- deformed, but not compressed (fluid)
- transmits pressure in all directions if deformed
describe the structure of annulus
- weight is 60-70% water
- dry weight
- 50-60% collagen → type I (resist tensile loading)
- 20% proteoglycans
- 10% elastic fibers
- 10-20 lamellae arranged in concentric rings
how does the thickness compare at different portions of the annulus?
- thicker toward center of disc, anteriorly, and laterally
- posteriorly the lamellae are thinner, finer, and more tightly packed
describe the structure of the vertebral endplate
- layers (0.6-1 mm thick)
- hyaline cartilage → toward vertebral body
- fibrocartilage → toward nucleus
- covers superior/inferior vertebral body
- covers nucleus, but not entire annulus
- encircled by ring apophasis
what is the function of IV discs?
- allow movement between vertebral bodies
- transmit loads between adjacent vertebral bodies
- absorbs and stores energy
how does the IV disc respond with compression?
annulus deforms and fluid “squeezed” from annulus
annulus braces the disc
nucles may be deformed, but not compressed
how does the IV disc absorb and store energy?
- collagen fibers of annulus stretch and store energy
- attenuates speed of force transmission between vertebral bodies
- elastic recoiling w/unloading = transmission of force to nucleus
T/F: IV discs are poorly vascularized
TRUE for the inner discs
there is some at the endplates at the outermost layers of annulus
describe the articulations of zygophyseal joints
inferior articular process of a vertebra with the superior process of adjacent vertebra
- superior facets = faces posteriomedially
- inferior facet = faces anteriolaterally
what is the function of facet joints in the lumbar spine?
guide and limit movement of spine
what type of joints are facet joints?
synovial
since facet joints are synovial, describe their structure
- synovial lining that is surrounded by a capsule
- 2 layers:
- outer collagen
- inner elastic fibers
- thick dorsally, reinforced by multifidi
- ballons superiorly and inferiorly
- tiny foramen in inferior and superior poles
- articular cartilage → 2 mm in height
T/F: the surface of facet joints are all the same
FALSE
they vary in shape and orientation
may be flat, or inferior facet may be concave
T/F: facet joints have fibro-adipose meniscoids
TRUE
they transmit loads and protect articular cartilage that would otherwise be exposed during motion
(they are also highly innervated)
describe the kinematics of lumbar flexion
- Facet joints
- forward sliding of Inf articular process on superior process by 5-8 mm
- “opening” of joints bilaterally, compression at end-range flexion
- Disc
- compression of annulus anteriorly
- stretching of annulus posteriorly
- Lateral foramen
- “open” (widen) as motion increases
describe the kinematics of lumbar extension
- Facet joints
- downward movement of inferior articular process
- compression of joint
- joints become weight-bearing
- Disc
- stretching of annulus anteriorly
- Lateral foramen
- “close” (narrow) as motion increases
describe the general trends for mean ranges for lumbar kinematics
- Mid to upper L/S get a good amount of lateral flexion
- Not much axial rotation throughout
- Less extension generally speaking
- Combined flexion and extension results in range from 13-16
what coupling motions occur at facet joints w/lateral flexion in the lumbar spine?
most commonly coupled w/extension
though variable in direction
what coupling motions occurs at facet joints with rotation in the lumbar spine?
coupling w/flexion and extension motions variable
describe lateral flexion and axial rotation coupling trends in the lumbar spine
- L1/L2-L3/L4 → contralateral rotation and lateral flexion motions
- L4/L5 → variable
- L5/S1 → ipsilateral lateral flexion and rotation motions
