Exam 1 (Anatomy & Kinesiology)

What are the functions of the spine?

• Shock absorption

• Rigid column

• Attachment for muscles & ligaments

• Protect spinal cord

• Support thorax

How many vertebrae are in each spinal region?

• 7 cervical

• 12 thoracic

• 5 lumbar

• 5 sacral (fused)

• 4 coccygeal (fused

What defines a spinal segment?

Two adjacent vertebrae and all structures connecting them (disc, facet joints, ligaments)

Which spinal structures are primary weight-bearing components?

Vertebral bodies and intervertebral discs (~80% load in lumbar spine)

What structures bear the remaining spinal load?

Facet (zygapophyseal) joints (~20%), depending on posture and curvature

What is the function of facet (zygapophyseal) joints?

Guide and limit intervertebral motion based on their orientation

What are the spinal curves?

• Lordosis (cervical & lumbar) - inward, anterior projection

• Kyphosis (thoracic & sacrococcygeal) - outward, posterior projection

What is the effect of an anterior tilt on the spine?

Increases lordosis

What is the effect of an posterior tilt on the spine?

Decreases lordosis

What does extreme extension/anterior pelvic tilt have on load distribution on the spine?

• Increase load on facets

• Ex: 60/40 load instead of 80/20

• Facet joint problem

What does extreme flexion/posterior pelvic tilt have on load distribution on the spine?

• Increase load on vertebral bodies/discs

• Ex: 90/10 load instead of 80/20

What is unique about the upper cervical spine (C0–C2)?

C0–C1 allows flexion/extension; C1–C2 allows the majority of cervical rotation due to horizontal facet orientation

What is the orientation of lower cervical facets (C2–C7)?

Approximately 45° between the frontal and transverse planes

What coupled motion occurs in the lower cervical spine?

Side-bending and rotation occur in the same direction.

What motion is most permitted in the thoracic spine?

Side-bending, due to frontal plane facet orientation

Why is thoracic motion limited compared to cervical and lumbar regions?

Rib cage attachments restrict motion

What is the “shingle effect”?

Inferiorly slanted thoracic spinous processes that overlap the vertebra below

Which thoracic vertebra is a transitional vertebra and why?

T12—upper facets are thoracic-oriented; lower facets are lumbar-oriented

What is the orientation of lumbar facet joints?

Sagittal plane

What primary motions are allowed in the lumbar spine?

Flexion and extension

Why is lumbar rotation limited?

Facet joint opposition restricts rotation

What are the anatomical components of the vertebral arch?

• transverse processes

• spinous process

• pedicles: connect arch to vert. body

• lamina: spinous to transverse

• articulating facets

What is the primary function of the sacrum?

load transfer between spine and pelvis

Why is motion minimal in the sacral and coccygeal regions?

Vertebrae are fused for stability

What are the three major factors determining spinal motion?

• Facet joint orientation

• disc thickness

• rib cage presence

How does disc thickness affect motion?

Thicker discs allow greater motion per segment

How do facet orientations determine regional spinal motion?

• Transverse plane → rotation

• Frontal plane → side-bending

• Sagittal plane → flexion/extension

What are the two main components of the intervertebral disc?

Nucleus pulposus and annulus fibrosus

Describe the nucleus pulposus.

• Gel-like

• 70–90% water

• avascular

• aneural

• redistributes load

Describe the annulus fibrosus.

15–25 concentric collagen rings oriented at alternating angles

Which portion of the annulus is innervated?

Outer one-third only

Why are posterolateral disc herniations common?

Annular fiber overlap is weakest posterolaterally and PLL is narrower in the lumbar spine

How does disc hydration change throughout the day?

• Decreases during weight-bearing

• increases during rest/sleep

How does movement affect disc health?

Promotes nutrient diffusion and waste removal through end plates

How do lumbar facets move during flexion?

Superior facets glide up and forward (open)

How do lumbar facets move during extension?

Superior facets glide down and backward (close).

What happens to the disc during flexion?

• Anterior compression

• posterior nuclear migration

What happens to the disc during extension?

• Posterior compression

• anterior nuclear migration

What is the primary action of the erector spinae group?

• Bilateral spinal extension

• unilateral side-bending

What muscles make up the erector spinae?

• Iliocostalis

• longissimus

• spinalis

What does the dorsal (afferent) side of the mixed nerve root carry?

Sensory info

What does the ventral (efferent) side of the mixed nerve root carry?

Motor info

What are the three types of spinal joints?

• Intervertebral disc: between adjacent vertebrae

• (Zyg)Apophyseal (Facet) joint: 2 between adjacent vertebrae

• Special/Atypical joints

What are the functions of the intervertebral discs?

• Absorb shock

• Disperse stress

• Bind vertebrae

• Contribute to spine curves

• Allow movement

What are the spinal ligaments?

• Anterior longitudinal ligament (ALL)

• Posterior longitudinal ligament (PLL)

• Ligamentum flavum

• Supraspinous & interspinous ligament

What is the function of the anterior longitudinal ligament?

• limits extension (runs anterior)

• minimizes anterior disc herniations

What is the function of the posterior longitudinal ligament?

• limits flexion (runs posterior)

• minimizes posterior disc herniations

What is the function of the ligamentum flavum?

limits flexion

What is the function of the supraspinous & interspinous ligament?

limit flexion

What is the role of the transversospinalis group?

Segmental stability and fine motor control

Name muscles of the transversospinalis group.

• Multifidus

• rotatores

• semispinalis

Why is multifidus clinically important?

Primary stabilizer of lumbar segments

Which muscles have larger moment arms for spinal extension?

Paraspinal muscles

Which muscle group is better suited for spinal stabilization?

Abdominal muscles (shorter moment arms but greater compressive control)

Why are abdominals important despite smaller moment arms?

They reduce shear forces and stabilize the spine through intra-abdominal pressure

What is the coupled motion in the lumbar spine?

side bending & rotation in the opposite direction

What is the coupled motion in the thoracic spine?

side bending & rotation in the opposite direction

What is the coupled motion in the lower cervical spine?

side bending & rotation in the same direction

What part of the thoracic spine is considered the functional/true t-spine segments?

T3-T9

What are the two trabecular systems?

• Vertical system: resists compressive force

• Oblique/Horizontal system: resist shear force

Where is the area of weakness in the thoracic spine trabecular systems?

anterior vertebral body

What are the flexion arthrokinematics of the AO (O-C1) Joint?

• Roll Anterior

• Slide Posterior

What are the extension arthrokinematics of the AO (O-C1) Joint?

• Roll Posterior

• Slide Anterior

What are the L Lateral Flexion arthrokinematics of the AO (O-C1) Joint?

• Roll Lateral (Left)

• Slide Medial (Right)

What are the R Lateral Flexion arthrokinematics of the AO (O-C1) Joint?

• Roll Lateral (Right)

• Slide Medial (Left)