Muscles of the Spinal Joints : Low Back

Question 1

What are the muscles of the low back?

Answer 1

1. Quadratus Lumborum
2. Muscles of the anterior abdominal wall
   - Rectus Abdominis
   - External Abdominal Oblique
   - Internal Abdominal Oblique
   - Transversus Abdominis
3. Psoas Minor

Question 2

What are the muscles of the anterior abdominal wall?

Answer 2

1. Rectus Abdominis
2. External Abdominal Oblique
3. Internal Abdominal Oblique
4. Transversus Abdominis

Question 3

What is the origin, insertion and actions of the Quadratus Lumborum?

Answer 3

O : 12th Rib and Transverse Processes of L1-L4
I : Posterior Iliac Crest
A :
1. Elevates the same side pelvis at the LS joint and laterally flexes the lower lumbar spine relative to upper lumbar spine
2. Anteriorly tilts the pelvis at the LS joint and extends the lower lumbar spine relative to the upper lumbar spine

Question 4

What is the origin, insertion and action of Rectus Abdominis?

Answer 4

O : Pubis
I : Xiphoid Process and Cartilage of ribs 5-7
A :
1. Flexes the trunk at the spinal joints
2. Laterally flexes the trunk at the spinal joints

Question 5

What is the origin, insertion and action of External Abdominal Oblique?

Answer 5

O : Anterior Iliac Crest, Pubic Bone, Abdominal Aponeurosis
I : Ribs 5-12
A :
1. Flexes the trunk at the spinal joints
2. Laterally flexes the trunk at the spinal joints
3. Contralaterally rotates the trunk at the spinal joints

Question 6

What is the origin, insertion and actions of Internal Abdominal Oblique?

Answer 6

O : Inguinal Ligament, Iliac Crest, Thoracolumbar Fascia
I : Ribs 10-12 and Abdominal Aponeurosis
A :
1. Flexes the trunk at the spinal joints
2. Laterally flexes the trunk at the spinal joints
3. Ipsilaterally rotates the trunk at the spinal joints

Question 7

What is the origin, insertion and actions of Transversus Abdominis?

Answer 7

O : Inguinal Ligament, Iliac Crest, Thoracolumbar Fascia and Lower Costal Cartilage
I : Abdominal Aponeurosis
A : Compresses Abdominopelvic Cavity