Muscles of the Back

Question 1

What are two classes of muscles in the back? - give definitions

Answer 1

• extrinsic: do not develop in back/ covering muscles

- intrinsic: develop embryologically in the back

Question 2

Give an overview of the superficial extrinsic muscles (movements of the shoulder)

Answer 2

• superficial: trapezius/ lat dorsi

- deep: levator scapulae/ rhomboids

Question 3

Give origin, insertion, action, innervation of trapezius

Answer 3

• O: nuchal ligament/ spinous processes of C7-12
• I: medial border of scapula
• A: upper - elevates, middle - retracts, lower - pulls scapula inferiorly
• innervated by spinal accessory nerve

Question 4

Give origin, insertion, action, innervation of lat dorsi

Answer 4

• O: spinous processes T6-12, iliac crest, thoracocolumbar fascia & 1st 3 ribs
• I: bicipital groove of humerus
• A: adductor/ depresses scapula
• innervated by thoracodorsal nerve

Question 5

Give origin, insertion, action, innervation of rhomboids

Answer 5

• O: minor = spinous process of T2-5/ major = spinous process of T2-5
• I: medial border of scapula
• A: retract/ rotate scapula

Question 6

Give origin, insertion, action, innervation of levator scapulae

Answer 6

• O: transverse processes of C1-4
• I: medial border of scapula
• A: elevates scapula
• anterior rami of C3-4, dorsal scapular nerve

Question 7

Which muscles are intermediate intrinsic muscles?

- give innervation

Answer 7

• serrator posterior inferior
• serrator posterior superior
• innervated by intercostal nerves

Question 8

Give origin and insertion/ action for intermediate intrinsic muscles

Answer 8

serrator posterior
- superior: nuchal ligament and spinous process of C7-T3
= elevates ribs 2-4
- inferior: spinous process T11-L3
= elevates ribs 9-12

Question 9

Which muscles are referred to as spinotransversalis?

Answer 9

• splenius capitis
• splenius cervicis
  (covering muscles - intrinsic muscles)

Question 10

Give the action and innervation of the muscles in spinotranversalis

Answer 10

elevate head and neck/ unilaterally: rotate/ lateral flexion

- innervated by posterior rami of spinal nerves

Question 11

Give origin and insertion of muscles in spinotransvesalis

Answer 11

O: nuchal ligament, spinous processes of C7-T6
I: = capitis: mastoid process & occipital bone
= cervicis: transverse processes of C1-3/4

Question 12

What is the name of the group of muscles which are superficial extrinsic muscles?
- where are they found? give innervation

Answer 12

erector spinae

• found posterolateral to spine between spinous processed & costal angle of ribs
• innervated by posterior rami of spinal nerves

Question 13

Name the muscles of the erector spinae

Answer 13

• iliocostalis
• longissimus
• spinalis

Question 14

What is the common tendinous origin of the erector spinae? what are the attachments?

Answer 14

• lower thoracic & lumbar vertebrae
• posterior part of iliac crest
• sacrum
• sacroiliac & supraspinous ligaments

Question 15

how can the muscles of the erector spinae be further divided?

Answer 15

into their superior attachments: lumborum, thoracis, cervic, capitis

Question 16

What are the actions of the erector spinae?

Answer 16

• extend vertebral column & head

- unilateral: lateral flexion of vertebral column

Question 17

What are the intermediate intrinsic muscles called? - give their innervation

Answer 17

transversospinales - posterior primary rami

Question 18

Name the muscles of the transversospinales and their actions

Answer 18

• semispinalis - extends & contralaterally roates head & vertebral column
• multifidus - stabilises vertebral column
• rotatores - stabiliser and proprioception

Question 19

Give origin and insertion of semispinalis

Answer 19

• O: transverse process of C4-T10

- I: fibres span 4-6 segments and attach to spinous processes of C2-4 & occipital bone

Question 20

Give origin and insertion of multifidus

Answer 20

• O: broad origin - sacrum, posterior iliac spine, origion of the erector spinae, mamillary processes of lumbar vertebrae, transverse processes of T1-3, articular processes of C4-7
• I: fibres span 2-4 segments to attach to spinous process

Question 21

Give origin and insertion of rotatores

Answer 21

O: transverse processes of vertebrae (particularly thoracic)
I: lamina & spinous processes of vertebrae - brevis (immediate)/ longus (2 segments superior)

Question 22

What are the three deep minor intrinsic muscles?

and their actions

Answer 22

• interspinales - stabiliser of vertebral column
• intertransversarii - aids in stabilising
• levatores costarum - elevates ribs/ assists with lateral flexion of vertebral column

Question 23

Give origins of interspinales and intertransversarii

Answer 23

• interspinales: span between spinous processes

- intertransversarii: span between transverse processes

Question 24

Give origins and insertions of levatores costarum

Answer 24

• O: tips of transverse processes of C7-T11 vertebrae

- I: ribs immediately below