Back Muscles

Question 1

Erector Spinae

Answer 1

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

Action: extends and laterally bends the trunk, neck and head

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

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

Question 2

Iliocostalis

Answer 2

Origin: iliac crest and sacrum

Insertion: angles of the ribs

Action: extends and laterally bends the trunk and neck

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C4-S5

Question 3

Interspinales

Answer 3

Origin: upper border of spinous process

Insertion: lower border of spinous process above

Action: extend trunk and neck

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-L5

Question 4

Intertransversarii

Answer 4

Origin: upper border of transverse process

Insertion: lower border of transverse process above

Action: laterally bend trunk and neck

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-L5

Question 5

Longissimus

Answer 5

Origin: transverse process at inferior vertebral levels

Insertion: transverse process at superior vertebral levels and mastoid process

Action: extends and laterally bends the trunk, neck and head

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-S1

Question 6

Multifidus

Answer 6

Origin: sacrum, transverse processes of C3-L5

Insertion: spinous processes 2-4 vertebral levels superior to their origin

Action: extend and laterally bend trunk and neck, rotate to opposite side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-L5

Question 7

Obliquus Capitis Inferior

Answer 7

Origin: spinous process of the axis

Insertion: transverse process of atlas

Action: rotates the head to the same side

Artery: occipital a.

Innervation: suboccipital nerve (DPR of C1)

Question 8

Obliquus Capitis Superior

Answer 8

Origin: transverse process of atlas

Insertion: occipital bone above inferior nuchal line

Action: extends the head, rotates the head to the same side

Artery: occipital a.

Innervation: suboccipital nerve (DPR of C1)

Question 9

Rectus Capitis Posterior Major

Answer 9

Origin: spinous process of axis

Insertion: inferior nuchal line

Action: extends the head, rotate to same side

Artery: occipital a.

Innervation: suboccipital nerve (DPR of C1)

Question 10

Rotatores

Answer 10

Origin: transverse processes

Insertion: long rotatores: spines 2 vertebrae above origin; short rotatores: spines 1 vertebrae above origin

Action: rotates the vertebral column to the opposite side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-L5

Question 11

Semispinalis

Answer 11

Origin: transverse processes of C7-T12

Insertion: capitis: back of skull between nuchal lines; cervicis & thoracis: spines 4-6 vertebrae above origin

Action: extends the trunk and laterally bends the trunk, rotates the trunk to the opposite side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C1-T12

Question 12

Spinalis

Answer 12

Origin: spinous processes at inferior vertebral levels

Insertion: spinous processes at superior vertebral levels and base of the skull

Action: extends and laterally bends trunk and neck

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Innervation: dorsal primary rami of spinal nerves C2-L3

Question 13

Splenius

Answer 13

Origin: ligamentum nuchae and spines C7-T6

Insertion: capitis: mastoid process & superior nuchal line laterally; cervicis: posterior tubercles of C1-C3 vertebrae

Action: extends and laterally bends neck and head; rotates head to same side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa.

Innervation: dorsal primary rami of spinal nerves C2-C6

Question 14

Splenius Capitis

Answer 14

Origin: ligamentum nuchae and spines of C7-T6 vertebrae

Insertion: mastoid process and lateral end of the superior nuchal line

Action: extends and laterally bends the neck and head, rotates head to the same side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa.

Innervation: dorsal primary rami of spinal nerves C2-C6

Question 15

Rectus Capitis Posterior Minor

Answer 15

Origin: posterior tubercle of atlas

Insertion: inferior nuchal line medially

Action: extends the head

Artery: occipital a.

Innervation: suboccipital nerve (DPR of C1)

Question 16

Splenius Cervicis

Answer 16

Origin: ligamentum nuchae and spines of C7-T6 vertebrae

Insertion: posterior tubercles of the transverse processes of C1-C3 vertebrae

Action: extends and laterally bends neck and head, rotates head to the same side

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa.

Innervation: dorsal primary rami of spinal nerves C2-C6