Anatomy of the Spine, Muscles, and Ligaments: Key Concepts for Students

Cervical Vertebrae Count & Curve

7 vertebrae; Lordotic curve

Thoracic Vertebrae Count & Curve

12 vertebrae; Kyphotic curve

Lumbar Vertebrae Count & Curve

5 vertebrae; Lordotic curve

Sacral Spine Curve

Kyphotic curve

Iliocostalis Muscle (Erector Spinae)

Most lateral muscle of the erector spinae group; attaches to ribs

Longissimus Muscle (Erector Spinae)

Intermediate muscle of the erector spinae group

Spinalis Muscle (Erector Spinae)

Most medial muscle of the erector spinae group; attaches along spinous processes

Erector Spinae Bilateral Action

Extends the vertebral column

Erector Spinae Unilateral Action

Laterally flexes the vertebral column to the same side

Multifidi & Rotatores Unilateral Action

Rotates the vertebral column to the opposite side

Quadratus Lumborum Action

Unilaterally laterally tilts pelvis and laterally flexes vertebral column; Bilaterally fixes 12th rib

Rectus Abdominis Action

Flexes the vertebral column and tilts pelvis posteriorly

External Oblique Unilateral Action

Laterally flexes to same side; rotates vertebral column to opposite side

Internal Oblique Unilateral Action

Laterally flexes to same side; rotates vertebral column to same side

Transverse Abdominis Action

Compresses abdominal contents

Intervertebral Disc Components

Nucleus pulposus (inner semigelatinous, 60-70% water) and Annulus fibrosus (outer multilayered fibers)

Number of Intervertebral Disks

23 discs (no disc between C0-C1 and C1-C2)

Ligament Stressed in Spinal Extension

Anterior longitudinal ligament

Ligaments Stressed in Spinal Flexion

Posterior longitudinal ligament, supraspinous, interspinous, and ligamentum flavum

Lumbar Plexus Roots & Major Branches

T12-L5 roots; forms Femoral nerve (posterior branches) and Obturator nerve (anterior branches)

External Intercostals Action

Draws ribs superiorly to assist with inhalation

Internal Intercostals Action

Draws ribs inferiorly to assist with exhalation