Vertebral Column & Back Muscles – Comprehensive Bullet-Point Notes

Instructor & Course Context

• Lecturer: Estelle Bishop, PhD
  • E-mail: Estelle.Bishop@uvm.edu
  • Course code: ANNB 6000 – Vertebral Column and Back Muscles
• Institution: The University of Vermont

Effective Study Strategies (as recommended in class)

• Quiz Yourself
  • Redraw or print blank diagrams; label bones, features, muscle attachments, innervations, actions.
• Peer Quizzing
  • Share written questions (e.g., a shared Google Drive).
  • Use real gross-anatomy photos (NetAnatomy).
  • Meet in the lab for in-person testing.
• Peer Teaching
  • Begin & end lab sessions with mini-lessons.
  • Rotate teaching roles outside of lab.
• Digital / Multimedia Aids
  • UVM Anatomy videos (Blackboard & lab iPads).
  • YouTube – Armando Hasudungan, Adapt to Perform, Ekhart Yoga, Man Flow Yoga.
  • NetAnatomy (web & iPhone).
  • 3D4 MED “Complete Anatomy” (annual subscription).
  • BioDigital (subscription-based 3-D anatomy).
• Ask for Help – reach out early to instructors, TAs, or classmates.

Learning Objectives (guide your self-assessment)

1. Identify & name bony landmarks of every vertebra.
2. Compare vertebrae across cervical, thoracic, lumbar, sacral, coccygeal regions.
3. Explain how specific joints generate spinal motion.
4. Relate cartilage & ligament positions to spinal support.
5. Distinguish superficial, intermediate, and deep back-muscle groups & their functions.
6. Describe orientation, innervation, & actions of suboccipital-triangle muscles.

Axial vs. Appendicular Skeleton Review

• Axial: skull, vertebral column, rib cage.
• Appendicular: upper & lower limb bones plus pectoral (clavicle, scapula) & pelvic girdles.

Key Surface & Bony Landmarks of the Back

• Skull: inion, superior & inferior nuchal lines, mastoid process.
• Scapula: spine, acromion, superior & inferior angles.
• Humerus, clavicle, iliac crest also serve as muscular anchor points.

Arrangement & Physiologic Curvatures of the Vertebral Column

• Region count:
  • Cervical $C1{-}C7$
  • Thoracic $T1{-}T12$
  • Lumbar $L1{-}L5$
  • Sacral $S1{-}S5$ (fused)
  • Coccygeal $Co1{-}Co4$ (fused).
• Primary (fetal/kyphotic): thoracic & sacral.
• Secondary (post-natal/lordotic): cervical (develops with head control) & lumbar (develops with bipedal gait).

Typical Vertebra – Superior-View Anatomy

• Vertebral body, arch (pedicles + laminae), vertebral foramen.
• Processes: transverse (lat.), spinous (post.), superior & inferior articular facets (form zygapophyseal joints).

Typical Vertebra – Lateral-View Highlights

• Inferior & superior vertebral notches align to create the intervertebral foramen (exit for spinal nerves).
• Facet-to-facet articulations = zygapophyseal joints (guide regional motion).

Regional Morphology at a Glance

• Cervical
  • Small body, large triangular foramen.
  • Transverse foramen for vertebral artery.
  • Bifid spinous process; slight inferior angle.
• Thoracic
  • Heart-shaped body.
  • Costal facets & demifacets on bodies & transverse processes (rib articulation).
  • Spinous process projects sharply inferiorly.
• Lumbar
  • Massive kidney-shaped body, small foramen.
  • Blunt spinous process.
  • Mammillary processes on superior facets.

Specialized Cervical Vertebrae

• Atlas (C1)
  • No body or spinous process; anterior & posterior arches with tubercles.
  • Large lateral masses → atlanto-occipital joint (≈ $50\%$ of cervical flex/ext).
  • Groove for vertebral artery.
• Axis (C2)
  • Odontoid process (dens) projects superiorly.
  • Atlanto-axial joint (dens + anterior arch of C1) provides ≈ $50\%$ of cervical rotation.

Sacrum & Coccyx Essentials

• Sacral promontory, anterior & posterior sacral foramina, sacral canal, sacral hiatus.
• Coccyx: vestigial tail; attachment for pelvic floor ligaments & muscles.

Ligamentous Support of the Spine

• Anterior Longitudinal Ligament (ALL) – anterior vertebral bodies; limits extension.
• Posterior Longitudinal Ligament (PLL) – posterior bodies; limits flexion.
• Ligamentum Flavum – elastic bands joining laminae; aids recoil to extension.
• Interspinous Ligament – between spinous processes.
• Supraspinous Ligament – tips of spines $C7\rightarrow sacrum$; expands into nuchal ligament $\,(C1{-}C7)$ for muscle attachment & head support.

Vertebral Spaces & Disc Anatomy

• Vertebral canal (stacked vertebral foramina) encloses spinal cord.
• Intervertebral disc in disc space between bodies:
  • Anulus fibrosus – concentric fibrocartilage layers.
  • Nucleus pulposus – gelatinous core; $\approx90\%$ water at birth → $\approx70\%$ by mid-age (clinical relevance: dehydration = height loss & herniation risk).
• Intervertebral foramen – passage for spinal nerve, vessels, dorsal root ganglion.

Functional Muscle Groups of the Back

• Superficial (extrinsic; upper limb movers): trapezius, latissimus dorsi, rhomboid major & minor, levator scapulae.
• Intermediate (respiratory accessory): serratus posterior superior & inferior.
• Deep (intrinsic; spine movers/stabilizers): splenius, erector spinae, transversospinalis, suboccipital.

Superficial Back Muscles – Key Innervation

• Trapezius – Accessory nerve (CN XI).
• Latissimus dorsi – Thoracodorsal nerve.
• Rhomboids (major & minor) – Dorsal scapular nerve.
• Levator scapulae – Dorsal scapular nerve.
  (Note: attachments & actions covered in a later unit.)

Intermediate Back Muscles – Attachments & Function

• Serratus Posterior Superior
  • Prox: nuchal ligament & spinous processes.
  • Dist: ribs 2-5.
  • Action: elevates ribs during inhalation.
  • Innervation: intercostal nerves T2-T5.
• Serratus Posterior Inferior
  • Prox: spinous processes T11-L2.
  • Dist: ribs 9-12.
  • Action: depresses ribs during exhalation.
  • Innervation: intercostal nerves T9-T12.

Deep Back – Splenius Group

• Splenius capitis & cervicis
  • Prox: nuchal ligament (capitis) + spinous processes (both).
  • Dist: mastoid process & superior nuchal line (capitis); cervical transverse processes (cervicis).
  • Action:
  – Bilateral: extend head/neck.
  – Unilateral: lateral flex & ipsilateral rotation.
  • Innervation: dorsal rami of cervical spinal nerves.

Deep Back – Erector Spinae (I Like Standing)

• Iliocostalis, Longissimus, Spinalis share:
  • Common (inferior) origin – thoracolumbar fascia, iliac crest, sacrum, spinous processes.
  • Distal patterns:
  – Iliocostalis → ribs & cervical transverse processes.
  – Longissimus → transverse processes & mastoid process (longissimus capitis).
  – Spinalis → spinous processes (cervical & thoracic).
  • Action:
  – Bilateral: spinal extension.
  – Unilateral: ipsilateral lateral flexion.
  • Innervation: dorsal rami.
• Thoracolumbar fascia: thick aponeurotic envelope enclosing erector group; provides lumbar stability & abdominal-wall muscle attachment.

Deep Back – Transversospinalis Group

• Semispinalis (spans ≈6 levels), Multifidus (≈4), Rotatores (≈2).
• Attachment rule: transverse process → superior spinous process (or occiput for semispinalis capitis).
• Actions:
  • Bilateral: spine extension (all); head extension (semispinalis capitis).
  • Unilateral: ipsilateral lateral flexion (all) with contralateral rotation for semispinalis & multifidus.
• Innervation: dorsal rami.

Suboccipital Triangle – Borders, Contents, Function

• Borders:
  • Rectus capitis posterior major (medial & superior).
  • Obliquus capitis superior (lateral & superior).
  • Obliquus capitis inferior (inferior).
• Floor: posterior atlanto-occipital membrane & posterior arch of C1.
• Roof: semispinalis capitis.
• Contents (all emerge centrally):
  • Vertebral artery (after exiting transverse foramen of C1).
  • Suboccipital nerve (dorsal ramus C1 – motor to all 4 muscles).
• Nearby: Greater occipital nerve (dorsal ramus C2 – sensory to posterior scalp) exits below obliquus capitis inferior.

Individual Suboccipital Muscles – Attachments & Motions

• Rectus Capitis Posterior Minor
  • C1 posterior tubercle → inferior nuchal line.
  • Bilateral: head extension; Unilateral: ipsilateral rotation.
• Rectus Capitis Posterior Major
  • C2 spinous process → inferior nuchal line.
  • Same actions as minor (larger moment arm).
• Obliquus Capitis Superior
  • C1 transverse process → inferior nuchal line.
  • Bilateral: extension.
  • Unilateral: lateral flexion (ipsilateral) & contralateral rotation.
• Obliquus Capitis Inferior
  • C2 spinous process → C1 transverse process.
  • Bilateral: extension.
  • Unilateral: strong ipsilateral rotation of atlas/head.

Vertebral Artery – Clinical & Practical Notes

• Origin: subclavian artery.
• Enters transverse foramen at C6, ascends through C6 → C1, curves medially across posterior arch of atlas, pierces dura to enter foramen magnum.
• Supplies posterior brain (basilar circulation).
• Path makes it vulnerable to trauma during extreme cervical rotation (e.g., chiropractic manipulation, sports injuries).

Dissection & Lab Integration

• Reflect superficial layers (trapezius, latissimus, rhomboids) to expose deeper structures.
• Sequentially remove splenius & semispinalis to see suboccipital region.
• Identify: 4 triangle muscles, vertebral artery, suboccipital & greater occipital nerves, bony landmarks.
• Practice drawing triangle elements to solidify 3-D relationships.

Real-World & Clinical Connections

• Disc dehydration (↓water from $90\%$ → $70\%$) contributes to degenerative disc disease & nerve compression.
• Rupture of ALL vs. PLL differentiates hyper-extension vs. hyper-flexion injuries (e.g., whiplash).
• Nuchal ligament palpation helps locate cervical midline for epidural/LP orientation.
• Weak multifidus implicated in chronic low-back pain; targeted strengthening improves lumbar stability.

Suggested Self-Testing Prompts

• Trace a path a spinal nerve travels from spinal cord out to body, naming every space & ligament it passes.
• Explain why thoracic spine has limited flexion/extension but robust rotation.
• Predict deficits after lesion of dorsal scapular nerve vs. accessory nerve.
• During a yoga pose showing lumbar lordosis, list the muscles actively contracting and the ligaments under tension.