Deep Back Muscles

Question 1

Serratus posterior inferior (Netter’s plates 171, 174, & 175)

Answer 1

Origin: Thoracolumbar fascia, spines of vertebrae T11-T12 and L1-L2

Insertion: Ribs 9-12, lateral to the angles

Innervation: Branches of the ventral primary rami of spinal nerves T9-T12

Blood supply: Intercostal arteries

Function: Depresses ribs 9 thru 12 and prevents ribs from elevating when the diaphragm contracts.

Question 2

Serratus posterior superior (Netter’s plate 175)

Answer 2

Origin: Ligamentum nuchae, spines of vertebrae C7 and T1-T3

Insertion: Ribs 1-4, lateral to the angles

Innervation: Branches of the ventral primary rami of spinal nerves T1-T4

Blood supply: Posterior intercostal aa. 1-4

Function: Elevates ribs 2 thru 5

Question 3

Splenius capitis (Netter’s Plate 174 & 175)

Answer 3

Origin: Nuchael ligament and spinous proccesses of C7 through T3

Insertion: Mastoid process of temporal bone and the latteral 1/3 of the superior nuchael line

Innervation: Dorsal rami of middle cervical nerves

Blood supply: Descending branch of occipital artery and the deep cervical artery

Function: Along with S. cervicis, draws head backwards and extends the neck.

By itself, it rotates the head to the left and right.

Question 4

Splenius cervicis (Netter’s 171, 174, & 175)

Answer 4

Origin: Spinous proccess of T3-T6

Insertion: Transverse processes of C1-C3

Innervation: Dorsal rami of lower cervical nerves

Blood supply: Descending branch of occipital artery and the deep cervical artery

Function:

Along with S. capitis, draws head backwards and extends the neck.

By itself, it rotates the head to the left and right.

Question 5

Erector Spinae Group (Illiocostalis, Longissimus, and Spinalis)

Answer 5

Origin: Iliac crest, sacrum, transverse and spinous processes of vertebrae and supraspinal ligament

Insertion: Angles of the ribs, transverse and spinous processes of vertebrae, posterior aspect of the skull

Innervation: Segmentally innervated by dorsal primary rami of spinal nerves C1-S5

Blood supply: Supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Function: Extends and laterally bends the trunk, neck and head

Question 6

Semispinalis

Answer 6

Origin: Transverse proccess of C4-T12

Insertion: Spinous proccesses of cervical and thoracic vertebrae

Innervation: Dorsal rami of spinal nerves

Blood supply: Occipital deep cervical and vertebral arteries, subcostal and posterior intercostals

Action: Extends head, neck and thorax. Rotates these things to the opposite side.

Question 7

Multifidus

Answer 7

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

Insertion: Spinous processes of vertebrae above, spanning two to four segments

Innervation: Dorsal rami of each region

Blood supply: Occipital deep cervical and vertebral arteries, subcostal and lumbar arteries, lateral sacral arteries

Action: Stabilizes spine

Question 8

Rotators

Answer 8

Origin: Transverse proccesses pf cervical, thoracic, and lumbar vertabrae.

Insertion: Lamina and transverse proccesses of spine

Innervation: Dorsal rami of spinal nerves

Blood supply: Occipital, deep cervical, and vertebral arteries. Intercostal arteries.

Action: Extends head, neck and thorax. Rotates these things to the opposite side.