Back Muscles

Question 1

trapezius

Answer 1

origin: external occipital protuberance; nuchal ligament; superior nuchal line; SP of C7-T12
insertion: spine of scapula; acromion, lateral 1/3 of clavicle
action: elevate, depress, rotate, retract scapula

blood supply: superficial branch of transverse cervical artery

innervation: cranial nerve XI (spinal accessory nerve); spinal nerves C3-C4

Question 2

latissimus dorsi

Answer 2

origin: SP of T7-T12; thoracolumbar fascia; iliac crest; ribs 9-12
insertion: floor of intertubercular sulcus on humerus
action: extend, adduct, medially rotate humerus

blood supply: thoracodorsal artery

innervation: thoracodorsal nerve (C6-8)

Question 3

rhomboid minor

Answer 3

origin: nuchal ligament, SP of C7-T1
insertion: medial border of scapula at level of scapular spine
action: retract, rotate, and hold scapula close to thoracic wall

blood supply: dorsal scapular vessels

innervation: dorsal scapular nerve (C5)

Question 4

rhomboid major

Answer 4

origin: SP of T2-T5
insertion: medial border of scapula inferior to scapular spine
action: retract, rotate, and hold scapula close to thoracic wall

blood supply: dorsal scapular vessels

innervation: dorsal scapular nerve (C5)

Question 5

levator scapulae

Answer 5

origin: TP of C1-C4
insertion: medial border of scapula from superior angle to spine
action: elevate and rotate scapula

blood supply: dorsal scapular vessels

innervation: dorsal scapular nerve (C5)

Question 6

serratus posterior superior

Answer 6

origin: nuchal ligament; SP of C7-T3
insertion: superior border of ribs 2-5
action: respiratory

blood supply: intercostal arteries

innervation: intercostal nerves T1-T4

Question 7

serratus posterior inferior

Answer 7

origin: SP of T11-L2
insertion: inferior borders of ribs 9-12
action: respiratory

blood supply: intercostal arteries

innervation: intercostal nerves T9-T12

Question 8

splenius capitus

Answer 8

origin: nuchal ligament; SP of C7-T3
insertion: mastoid process of temporal bone; lateral 1/3 of superior nuchal line
action: extends head; laterally bends and rotates face

blood supply: descending branch of occipital artery

innervation: dorsal rami of middle cervical nerves

Question 9

splenius cervicis

Answer 9

origin: SP of T3-T6
insertion: TP of C1-C3/C4
action: extends neck; laterally bends and rotates neck

blood supply: descending branch of occipital artery

innervation: dorsal rami of lower cervical nerves

Question 10

iliocostalis

Answer 10

origin: iliac crest; sacrum; sacro-iliac ligaments; SP of lower lumbar and sacral vertebrae
insertion: angles of lower ribs; cervical TPs
action: extend and laterally bend vertebral column and head

blood supply:
cervicis- occipital, deep cervical, and vertebral arteries
thoracis: dorsal branches of posterior intercostal, subcostal, and lumbar arteries
lumborum: dorsal branches of lateral sacral arteries

innervation: dorsal rami of each region

Question 11

longissimus

Answer 11

origin: iliac crest; sacrum; sacro-iliac ligaments; SP of lower lumbar and sacral vertebrae
insertion: between tubercles and angles of ribs; TP of thoracic and cervical vertebrae; mastoid process
action: extend and laterally bend vertebral column and head

blood supply:
cervicis- occipital, deep cervical, and vertebral arteries
thoracis: dorsal branches of posterior intercostal, subcostal, and lumbar arteries
lumborum: dorsal branches of lateral sacral arteries

innervation: dorsal rami of each region

Question 12

spinalis

Answer 12

origin: iliac crest; sacrum; sacro-iliac ligaments; SP of lower lumbar and sacral vertebrae
insertion: SP of upper thoracic and mid-cervical vertebrae
action: extend and laterally bend vertebral column and head

blood supply:
cervicis- occipital, deep cervical, and vertebral arteries
thoracis: dorsal branches of posterior intercostal, subcostal, and lumbar arteries
lumborum: dorsal branches of lateral sacral arteries

innervation: dorsal rami of each region

Question 13

semispinalis

Answer 13

origin: TP of C4-T10
insertion: occipital bone (capitus); SP of upper thoracic and cervical regions (cervicis and thoracis)–span 4-6 segments
action: extend head and thoracic and cervical regions of column

blood supply:
cervical–occipital, deep cervical, vertebral arteries
thoracic: dorsal branches of posterior intercostal arteries

innervation: dorsal rami of each region

Question 14

multifidus

Answer 14

origin: sacrum, ilium, TP of T-T12, articular processes of C4-C7
insertion: SP of vertebrae above, spanning 1-4 segments
action: stabilize spine

blood supply:
cervicis- occipital, deep cervical, and vertebral arteries
thoracis: dorsal branches of posterior intercostal, subcostal, and lumbar arteries
lumborum: dorsal branches of lateral sacral arteries

innervation: dorsal rami of each region

Question 15

rotatores

Answer 15

origin: TP; best developed in thoracic region
insertion: TP or SP of 1-2 vertebrae above (brevis and longus, respectively)
action: stabilize, extend, rotate spine

blood supply: dorsal branches of segmental arteries

innervation: dorsal rami of each region

Question 16

obliquus capitis inferior

Answer 16

origin: SP of C2
insertion: TP of C1
action: rotates atlas to turn face to same side

blood supply: vertebral artery; descending branch of occipital artery

innervation: suboccipital nerve (dorsal rami of C1)

Question 17

obliquus capitis superior

Answer 17

origin: TP of C1
insertion: occipital bone between superior and inferior nuchal lines
action: extend and bend head laterally

blood supply: vertebral artery; descending branch of occipital artery

innervation: suboccipital nerve (dorsal rami of C1)

Question 18

rectus capitis posterior major

Answer 18

origin: SP of C2
insertion: inferior nuchal line
action: extend and rotate head to same side

blood supply: vertebral artery; descending branch of occipital artery

innervation: suboccipital nerve (dorsal rami of C1)

Question 19

rectus capitis posterior minor

Answer 19

origin: posterior tubercle of posterior arch of C1
insertion: inferior nuchal line
action: extend head

blood supply: vertebral artery; descending branch of occipital artery

innervation: suboccipital nerve (dorsal rami of C1)