Deep Intrinsic

Question 1

Semispinalis

Answer 1

Origin: transverse processes of C4-T12

Insertion: spinous processes of cervical and thoracic regions (spans 5-6 levels)

Innervation: dorsal rami of spinal nerves

Blood Supply: cervical portions - occipital artery, deep cervical artery, and vertebral artery, thoracic portions - dorsal branches of posterior intercostal arteries

Action: extend head, neck, and thorax and rotates head, neck, and thorax to opposite side

Question 2

Multifidus

Answer 2

Origin: sacrum, ilium, transverse processes of T1-T12, and articular processes of C4-C7

Insertion: spinous processes of vertebrae above, spanning 2-4 levels

Innervation: dorsal rami of each region

Blood Supply: cervical portions - occipital, deep cervical, and vertebral arteries, thoracic portions - dorsal branches of posterior intercostal, subcostal, and lumbar arteries, sacral portions - dorsal branches of lateral sacral arteries

Action: stabilizes spine

Question 3

Rotatores

Answer 3

Origin: transverse processes of cervical, thoracic, and lumbar regions

Insertion: lamina and transverse process of spine above, spanning one or two segments

Innervation: dorsal rami of spinal nerves

Blood Supply: dorsal branches of segmental arteries

Action: stabilizes, extends, and rotates spine