Muscle | Function | Origin/Insertion | Innervation | Layer | Location |
Latissimus dorsi | Extends, adducts, and medially rotates arm; raises body toward arms during climbing stairs | Origin: T6 - T12 sp, Thoracolumbar fascia, iliac crest, lower 3-4 ribs. Insertion: Humerus | thoracodorsal nerve | Layer 1 | fan-shaped muscle on lower back |
Levator scapula | elevates scapula | ORIGIN: C1 - C4 transverse processes, INSERTION: medial border (superior angle) of scapula | dorsal scapular and cervical nerves | Layer 2 (extrinsic muscles) | (blank) |
Rhomboid major & minor | retract scapula, rorate scapula, fix scapula to thoracic wall | ORIGIN: Nuchal ligament, Spinous processes; INSERTION: medial end of spine of scapula | dorsal scapular nerve | Layer 2 (extrinsic muscles) | Superior to Rhomboid Major between scapula and vertebrae |
Serratus posterior superior | elevate ribs, move ribs | ORIGIN: nuchal ligament and C7 - T3 spinous processes; INSERTION: ribs 2-4 | intercostal nerves | Layer 3 (extrinsic muscles) | Under Rhomboids |
Serratus posterior inferior | depress ribs | ORIGIN: T11 - L2 spinous processes, INSERTION: ribs 8 -12 | intercostal nerves | Layer 3 (extrinsic muscles) | Under lats |
Splenius capitis (head) /cervicis (neck) | UNILATERAL: Rotate, sidebend HEAD/NECK to same side; BILATERAL: Extension | Upper 6 thoracic vertebrae to upper 4 cervical vertebrae & posterior skull | dorsal primary rami of spinal nerves C2-C6 | Layer 4 (intrinsic muscles) | (blank) |
Iliocostalis | Elevate/depress ribs; BILATERALLY: extend spine and head; UNILATERALLY :flex spine | Longitudinal Orientation: Spans from skull to pelvis | dorsal primary rami of spinal nerves C4-S5 | Layer 5: erector spinae | (blank) |
Longissimus (cervicis & capitis) | Ipsilateral Rotation and laterally flex the neck | Longitudinal Orientation: Longitudinal Orientation: Spans from skull to pelvis | dorsal primary rami of spinal nerves C1-S1 | Layer 5: erector spinae | (blank) |
Spinalis | BILATERALLY: extend spine and head; UNILATERALLY :flex spine | Longitudinal Orientation: Spans from skull to pelvis | dorsal primary rami of spinal nerves C2-L3 | Layer 5: erector spinae | (blank) |
Semispinalis (capitis,cervicis, thoracis) | UNILATERALLY: extends and rotates to opp side; BILATERALLY: extends | ORIGIN: transverse processes of C7-T12; INSERTION: sp's of thoracic and cervical vertebra | dorsal primary rami of spinal nerves C1-T12 | layer 6 DEEPEST BACK MMS, Transverso-spinalis | spans 4-6 segments |
Multifidus | UNILATERALLY: Rotate to opp side; BILATERALLY: stabilize w/ minimal extension | ORIGIN: sacrum, transverse processes of C3-L5, INSERTION: spinous processes 2-4 vertebral levels superior to their origin | dorsal primary rami of spinal nerves C1-L5 | layer 6 DEEPEST BACK MMS, Transverso-spinalis | spans 2-4 segments, thickest in lumbar region |
Rotatores | UNILATERALLY: Rotate to opp side; BILATERALLY: stabilize w/ minimal extension | ORIGIN: transverse processes; INSERTION: long rotatores: spines 2 vertebrae above origin; short rotatores: spines 1 vertebrae above origin | dorsal primary rami of spinal nerves C1-L5 | layer 6 DEEPEST BACK MMS, Transverso-spinalis | thoracic region best development |
Interspinales | stabilize w/ minimal extension | ORIGIN: upper border of spinous process; INSERTION: angles of the ribs | dorsal primary rami of spinal nerves C1-L5 | Deep muscle | (blank) |
Intertransversarii | stabilize w/ minimal extension | ORIGIN: upper border of transverse process; INSERTION: lower border of transverse process above | dorsal primary rami of spinal nerves C1-L5 | Deep muscle | (blank) |
Trapezius | Upper area elevates scapula,Lower area depresses and lowers shoulder,entire muscle retracts scapula | ORIGIN: Occiput, nuchal ligament, C7 - T12 SP's. INSERTION: clavicle, acromion, and spine of scapula | ORIGIN: Occiput, nuchal ligament, C7 - T12 SP's. INSERTION: clavicle, acromion, and spine of scapula | Layer 1 | Covers upper back;attaches upper limb to trunk |
Erector Spinae Group | Unilateral contraction = ipsilateral side bending; Bilateral contraction = extension | from skull to pelvis | Dorsal primary rami | I LOVE SPAGHETTI muscles | Illiocostalis, longissimus, spinalis |
Longissimus thoracis | Depress the ribs | ORIGIN: Posterior iliac crest and sacrum; sp's of lumbar vertebra; INSERTION: ribs, Thoracic and Cervical transverse processes, and occiput | dorsal primary rami of spinal nerves C1-S1 | Layer 5: erector spinae | (blank) |