Lecture 7 - Muscles Of The Posterior Trunk

Question 1

What are the 2 main groups of the posterior trunk muscles?

Answer 1

• extrinsic
• intrinsic

Question 2

What are intrinsic muscles?

Answer 2

• muscles that extend from the pelvis to the skull
• broken down into 3 groups

Question 3

What are the 3 groups of intrinsic muscles?

Answer 3

• superficial
• intermediate
• deep

Question 4

Which 3 muscles are apart of the intrinsic intermediate group?

Answer 4

• part of the erector spinal group:
• iliocostalis - has 3 distinct portions; iliocostalis lumbroum, thoracis, & cervicis
• longissimus - has 3 distinct portions; longissimus thoracis, cervicis, & capitus
• spinalis - has 3 distinct portions; spinalis thoracis, cervicis, & capitus

Question 5

Which 3 muscles are apart of the intrinsic deep group?

Answer 5

• part of the Transversospinalis group:
• semispinalis
• multifidus
• rotatores

Question 6

What is the erector spinae group?

Answer 6

• described as a single muscles, but compromised of 3 muscles
• Large column of muscle on either side of the vertebral column in a groove created by the spinous processes & the angles of the ribs
• The 3 muscles have a common origin, Innervation & main action, but a difference in insertions

Question 7

What is the origin/insertion/Innervation/main action of the iliocostalis?

Answer 7

• O: Posterior iliac crest, posterior surface of sacrum, sacro-iliac ligaments, sacral & lumbar spinous processes, supraspinous ligament
• I: Attaches to the angle of the ribs above & ultimately on the transverse processes of C4-C7
• Inn: Segmental
• MA: Bilaterally - vertebral column (spine) extension, Unilaterally - vertebral column (spine) side flexion

Question 8

What is the origin/insertion/Innervation/main action of the longissimus?

Answer 8

• O: Posterior iliac crest, posterior surface of sacrum, sacro-iliac ligaments, sacral & lumbar spinous processes, supraspinous ligament
• I: Transverse process of the vertebrae above & up as far as the mastoid process of the temporal bone
• Inn: Segmental
• MA: Bilaterally - vertebral column (spine) extension, Unilaterally - vertebral column (spine) side flexion

Question 9

What is the origin/insertion/Innervation/main action of the spinalis?

Answer 9

• O: Posterior iliac crest, posterior surface of sacrum, sacro-iliac ligaments, sacral & lumbar spinous processes, supraspinous ligament
• I: Spinous processes up to C2
• Inn: Segmental
• MA: Bilaterally - vertebral column (spine) extension, Unilaterally - vertebral column (spine) side flexion

Question 10

What is the Transversospinalis muscle group?

Answer 10

• Occupy the ‘gutter’ between transverse & spinous processes
• Common attachment points: Transverse process of one vertebrae to spinous processes of more superior vertebrae
• also Assist with vertebral column (spine) extension & stabilizing individual vertebrae

Question 11

What are the 3 muscles of the posterior abdominal wall?

Answer 11

• psoas major
• iliacus
• quadratus lumborum

Question 12

What is the origin/insertion/Innervation/main action of the psoas major?

Answer 12

• O: Anterior bodies, discs, transverse processes of the lumbar vertebrae
• I: Lesser trochanter of the femur
• Inn: Anterior rami of L1-L3
• MA: Hip flexion, stabilize hip joint with iliacus, & assists with trunk side flexion when acting unilaterally

Question 13

What is the origin/insertion/Innervation/main action of the iliacus?

Answer 13

• O: Superior 2/3 iliac fossa, anterior sacro-iliac ligaments
• I: Lesser trochanter of the femur (fuses with tendon of psoas major)
• Inn: Femoral nerve (L2-L4)
• MA: Hip felxion & Helps stabilize hip joint with psoas major

Question 14

What is the origin/insertion/Innervation/main action of the quadratus lumbroum?

Answer 14

• O: Transverse processes of L5, iliolumbar ligament, iliac crest
• I: Inferior border of rib 12, transverse processes of L1-L4
• Inn: Anterior rami of T12 & L1-L4
• MA: Side flexion of the lumbar spine (unilateral) & Some extension of the lumbar spine (bilateral)