Back Muscles

Question 1

Trapezius - origin, insertion, innervation, artery, actions

Answer 1

Origin - medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of vertebra C7-T12

Insertion - Lateral third of clavicle, medial side of acromion, upper crest of scapular spine

Innervation - Motor: spinal accessory (XI); proprioception: C3-C4

Artery - Transverse cervical artery, dorsal scapular artery, posterior intercostal artery

Actions - Elevate, depress and retract the scapula; rotate the glenoid surface superiorly (arm up)

Question 2

Latissimus dorsi - origin, insertion, innervation, artery, actions

Answer 2

Origin - vertebral spines from T6-12, thoracolumbar fascia
posterior third of the iliac crest
lower 3 or 4 ribs
sometimes from inferior angle of scapula

Insertion - floor of intertubercular groove on the humerus

Innervation - thoracodorsal nerve (C6, 7, 8)

Artery - thoracodorsal artery,
dorsal perforating branches of 9th, 10th, 11th posterior intercostal
subcostal
first three lumbar arteries

Actions - extends, adducts, and medially rotates arm

Question 3

Rhomboid major - origin, insertion, innervation, artery, actions

Answer 3

Origin - spines of vertebrae T2-5

Insertion - medial border of scapula inferior to spine of scapula

Innervation - dorsal scapular nerve (C4, 5)

Artery - dorsal scapular artery

Actions - retracts scapula and rotates the scapula inferiorly

Question 4

Rhomboid minor - origin, insertion, innervation, artery, actions

Answer 4

Origin - inferior end of ligamentum nuchae, spines of vertebra C7 and T1

Insertion - medial border of scapula at the root of spine of scapula

Innervation - dorsal scapular nerve (C4, 5)

Artery - dorsal scapular artery

Actions - retracts scapula and rotates the scapula inferiorly

Question 5

Levator scapulae - origin, insertion, innervation, artery, actions

Answer 5

Origin - posterior tubercles of C1-4 vertebra

Insertion - medial border of scapula - spine to superior angle

Innervation - dorsal scapular nerve (C4, C5); anterior primary rami of C3, C4

Artery - dorsal scapular artery

Actions - elevates medial part of scapula, causes inferior rotation of glenoid cavity

Question 6

Serratus Posterior Superior - origin, insertion, innervation, artery, actions

Answer 6

Origin - nuchal ligament, spinous process of C7-T3

Insertion - superior borders of ribs 2-5

Innervation - anterior primary rami (first four)

Artery - posterior intercostal artery

Action - elevate ribs, proprioception

Question 7

Serratus Posterior Inferior - origin, insertion, innervation, artery, actions

Answer 7

Origin - spinous process T11-L2

Insertion - inferior borders of ribs 9-12

Innervation - anterior primary rami (last four)

Artery - posterior intercostal

Action - depress ribs, proprioception

Question 8

Splenius - origin, insertion, innervation, artery, actions

Answer 8

Origin - ligamentum nuchae and spinous process C7-T6

Insertion -
Capitis: mastoid process and superior nuchal line
Cervicis: posterior tubercles of transverse process of C1-3

Innervation - dorsal primary rami of C2-6

Artery - occipital artery, deep cervical artery

Action -
Bilateral contraction: extends head and neck
Unilateral contraction: laterally flexes neck and head, rotates head ipsilaterally

Question 9

Erector Spinae - origin

Answer 9

iliac crest
Sacrum
processes of lower lumbar vertebra and sacrum
supraspinous ligament
sacrospinous ligament

Question 10

Erector Spinae - insertion

(Spinalis, Longissimus, and Iliocostalis)

Answer 10

Spinalis: Spinous processes of superior vertebral levels, cranium

Longissimus: Transverse process of superior vertebral levels, mastoid process

Iliocostalis: angles of lower ribs, cervical transverse process

Question 11

Erector Spinae - innervation

Answer 11

Dorsal primary rami of spinal nerves

Question 12

Erector Spinae - action

Answer 12

bilateral contraction extends back and head
unilateral contraction laterally bends trunk and neck

Question 13

Erector Spinae - artery

Answer 13

Occipital artery
Deep cervical artery
Vertebral artery
Posterior intercostal artery
Subcostal artery
Lumbar artery
Lateral sacral artery

Question 14

Transversospinalis group - origin

(Semispinalis, multifidus, rotatores)

Answer 14

Semispinalis: transverse processes of C4-T12

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

Rotatores: transverse processes

Question 15

Transversospinalis group - insertion

(Semispinalis, multifidus, rotatores)

Answer 15

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

Multifidus: spinous process 2-4 vertebra levels superior to origin

Rotatores: spinous process 2 vertebrae above origin (longus) or 1 vertebra above origin (brevis)

Question 16

Transversospinalis group - innervation

Answer 16

Dorsal primary rami of spinal nerves

Question 17

Transversospinalis group - action

Answer 17

Bilateral contraction extends trunk
unilateral contraction rotates trunk contralaterally
stabilizes spine

Question 18

Transversospinalis group - artery

Answer 18

Supplied segmentally

Occipital a.
Deep Cervical a.
Vertebral a.
Posterior intercostal a.
Subcostal a.
Lumbar a.
(semispinalis and multifidus only) Lateral sacral a.

Question 19

Obliquus capitis inferior

Answer 19

origin - spinous process of the axis
insertion - transverse process of the atlas
innervation - suboccipital nerve
artery - vertebral a, occipital a
action - rotates head ipsilaterally

Question 20

Obliquus capitis superior

Answer 20

origin - transverse process of the atlas
insertion - occipital bone inferior to nuchal line
innervation - suboccipital nerve
artery - vertebral a, occipital a
action - extends and bends head laterally

Question 21

Rectus capitis posterior major

Answer 21

origin - spinous process of the axis
insertion - inferior nuchal line
innervation - suboccipital nerve
artery - vertebral a, occipital a
action - extends head, rotates ipsilaterally

Question 22

Rectus capitis posterior minor

Answer 22

origin - posterior tubercle of atlas
insertion - inferior nuchal line medially
innervation - suboccipital nerve
artery - vertebral a, occipital a
action - extends head, rotates ipsilaterally