Muscles of the Trunk

Question 1

Multifidus

Answer 1

O:
Laminae of S4-C2
Including facet capsule
May be absent in thoracic region

I:
Superomedially 2-4 vertebrae to SP

A: 
Unilaterally
  -Lateral flexion of vertebral column 
  -Opposite rotation
Bilaterally 
  -Extend trunk 
  -Stabilize vertebral column 

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 2

Rotatores (Longus, Brevis)

Answer 2

O:
TP of whole vertebral column

I:
Brevis–superomedially to SP of next vert
Longus–superomedially of 2nd SP

A:
Rotate superior vertebrae to opposite side and bilaterally stabilizes column

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 3

Semispinalis (thoracis, cervicis, capitis)

Answer 3

O:
thoracis–TP of T6-T10
cervicis–TP of T1-T6
capitis–TP of T1-T6 and C7 articular process

I:
thoracis–SP of T1-T4 and C6-C7
cervicis–SP of C2-C5
capitis–inferior to superior nuchal line

A:
thoracis and cervicis–extend vertebral column
capitis
-bilaterally extends head
-unilaterally rotates trunk and head to opposite side

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 4

Iliocostalis (lumborum, thoracis, cervicis)

Answer 4

O:
Common for all 3
-Broad tendon from posterior iliac crest
-Sacrum, sacroiliac ligaments
-SP of sacral and inferior lumbar vertebrae

I:
Lumborum–inferior border of angle of ribs 12-6
Thoracis–all ribs
Cervicis–Ribs 1-6 and posterior tubercles of C4-C6

A: 
Unilaterally 
  -Laterally flex head and vertebral column to same side 
Bilaterally
  -Extensors of head and trunk 

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 5

Longissimus (Thoracis, cervicis, capitis)

Answer 5

O:
Common broad tendon from posterior iliac crest
Cervicis and capitis–TP at lower levels

I:
Thoracis–tips of TP of T1-T12 and tubercles of inferior borders of ribs 9+10
Cervicis–superior thoracic TP to cervical TP
Capitis–arises with cervicis and attaches to mastoid process

A: 
Unilaterally 
  -Flex head and vertebral column to same side 
Bilaterally
  -Extend head and trunk 
Capitis 
  -Rotates head to same side 

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 6

Spinalis (thoracis, cervicis, capitus)

Answer 6

O:
Common, from SP

I:
Thoracis–tips of SP of thoracic vertebrae
Cervicis–ligamentum nuchae to axis
Capitis–blends with cervicis

A:
Extends vertebral column and head

N:
Dorsal rami of cerv, thoracic, lumbar spinal nerves

Question 7

Splenius (cervicis, capitis)

Answer 7

O:
Cervicis–SP of T3-6
Capitis–SP of C7-T4 and ligamentum nuchae

I:
cervicis–TP of C2-C5
capitis–lateral part of superior nuchal line and mastoid process

A:
Bilaterally
-Contraction–extension of cervical region
Unilaterally
-contraction–lateral flexion and rotation to same side

N:
Dorsal rami of spinal nerves C3-C5 (capitis), C4-C8 (cerv)

Question 8

Obliquus Capitis Superior (Suboccipital Triangle)

Answer 8

O:
TP of C1

I:
Occipital bone
Deep to splenius, superficial to rectus capitis

A:
Rotation at AA joint
Stabilize occipital on C1
Extension and minor lateral flexion at AO

N:
Dorsal rami of C1 (suboccipital nerve)

Question 9

Obliquus Capitis Inferior (Suboccipital Triangle)

Answer 9

O:
SP of C2

I:
TP of C1

A:
Ipsilateral rotation of AA joint

N:
Dorsal rami of C1 (suboccipital nerve)

Question 10

Rectus Capitis Posterior Major (Suboccipital Triangle)

Answer 10

O:
SP of C2

I:
Occipital bone lateral to midline at inferior nuchal line

A:
Extension at AO joint and ipsilateral rotation at AA

N:
Dorsal rami of C1 (suboccipital nerve)

Question 11

Rectus Capitis Posterior Minor (Suboccipital Triangle)

Answer 11

O:
Posterior tubercle of C1

I: 
Occipital bone (Medial to R cap posterior major) 

A:
Extension at AO joint

N:
Dorsal rami of C1 (suboccipital nerve)

Question 12

Levator Costarum

Answer 12

O:
Tips of thoracic TP

I:
Inferolaterally to angle of inferior adjacent rib

A:
Elevate ribs during inspiration

N:
Dorsal rami of thoracic spinal nerves

Question 13

Quadratus Lumborum

Answer 13

O:
Iliolumbar ligament and internal lip of iliac crest

I:
Tips of lumbar TP, inferior border of rib 12

A:
Extends and laterally flexes vertebral column
Fixes rib 12 during inspiration

N:
Branches of ventral rami of T12, L1-L3(4)

Question 14

Psoas Major

Answer 14

O:
TP of lumbar vertebrae
Sides of body of T12, L1-L5 and IV discs

I:
Lesser trochanter of femur

A:
Increase lumbar lordosis
Assist in lateral flexion
Flex hip, pelvis on trunk

N:
Lumbar plexus
Branches of primary ventral rami L1-L4

Question 15

Rectus Abdominis

Answer 15

O:
Pubic crest and symphysis

I:
Costal cartilages 5-7
Xyphoid process

A:
Flexes trunk

N:
Ventral rami of spinal nerves T5-T12

Question 16

External Abdominal Oblique

Answer 16

O:
External surface of ribs 5-8 (anterior fibers)
Ribs 9-12 (lateral fibers)

I:
Outer lip of iliac crest
Linea alba via aponeurosis

A: 
Bilaterally 
  -Flex trunk lateral fibers act on lumbar region to posteriorly tilt pelvis
Unilaterally 
  -Rotate to opposite side 
  -Compress abdomen

N:
Ventral rami of spinal nerves T5-T12

Question 17

Internal Abdominal Oblique

Answer 17

O:
Lateral 2/3 of inguinal ligament of iliac crest
Thoracolumbar fascia

I:
Crest of pubis
Pectineal line
Linea alba

A:
Upper anterior fibers–flex trunk
Unilaterally
-work with external oblique of opposite side to rotate trunk

N:
Ventral rami of spinal nervers T7-T12
Iliohypogastric and ilioinguinal nerves

Question 18

Transverse Abdominis

Answer 18

O: 
Lower 6 ribs 
Thoracolumbar fascia (attach TP of lumbar vert)
Iliac crest 
Inguinal ligament 

I:
Linea alba
Pubic crest

A:
Stabilize trunk via fixation of linea alba
Compress abdomen

N:
Ventral rami of spinal nerves T7-T12
Iliohypogastric and ilioinguinal nerves