Level 3 Muscles Overview - Abdominals

Question 1

External Obliques

Answer 1

Location:
Side of torso

Joints crossed:
Intervertebral joints of lumbar and thoracic vertebrae

Actions:

• acting unilaterally: pulls the torso to the side (lateral flexion)
• acting unilaterally: turns the torso (rotation)
• acting bilaterally: bends the torso forwards (flexion)

Origin:
Lower eight ribs

Insertion:
Iliac crest and via the abdominal aponeurosis (white sheet of connective tissue) to the linea alba

Question 2

Internal Obliques

Answer 2

Location:
Side of the torso

Joints crossed:
Intervertebral joints of lumbar and thoracic vertebrae

Actions:

• acting unilaterally: pulls the torso to the side (lateral flexion)
• acting unilaterally: turns the torso (rotation)
• acting bilaterally: bends the torso forwards (flexion)

Origin:
Thoracolumbar fascia, iliac crest and inguinal ligament

Insertion:
Cartilage of lower three or four ribs and via the abdominal aponeurosis to the linear alba

Question 3

Transverse Abdominis

Answer 3

Location:
Side of torso

Joints crossed:
Intervertebral joints of lumbar vertebrae

Action:
- compresses the abdominal contents

Origin:
Cartilage of lower six ribs, thoracolumbar fascia, iliac crest and inguinal ligament

Insertion:
Via the abdominal aponeurosis to the linea alba

Question 4

Erector Spinae

Answer 4

Location:
On the back, either side of the vertebral column

Joints crossed:
Intervertebral joints

Actions:

• acting bilaterally: straightens the spine (extension)
• acting unilaterally: assists in pulling the torso to the side (lateral flexion)

Origin:
Sacrum and iliac crest

Insertion:
Ribs, transverse process of vertebrae and finally to the cranium

Question 5

Multifidus

Answer 5

Location:
On the back, either side of the vertebral column

Joints crossed:
All intervertebral joints

Actions:

• acting bilaterally: straightens the spine (extension)
• acting unilaterally: assists in pulling the torso to the side (lateral flexion)
• acting unilaterally: assists in turning the torso (rotation)

Origin:
Sacrum and mamillary/transverse processes of each vertebrae

Insertion:
Spinous process, two to four vertebrae above the origin

Question 6

Quadratus Lumborum

Answer 6

Location:
Either side of the vertebral column

Joints crossed:
Lumbar intervertebral joints

Action:
- pulls the torso to the side (lateral flexion)

Origin:
Iliac crest and iliolumbar ligament

Insertion:
Transverse processes of upper four lumbar vertebrae and lower margin of 12th rib

Question 7

Pelvic Floor Muscles

Answer 7

Location:
Several muscles at the bottom of the pelvis between the pubis and coccyx and surrounding front and back passages

Actions:

• support of the pelvic contents (bladder, intestines, uterus in females)
• continence as part of urinary and anal sphincters

Origin:
Ischium, pubis and associated connective tissue

Insertion:
Sacrum, coccyx and associated connective tissue

Question 8

Rectus Abdominis

Answer 8

Location:
Front of the torso

Joints crossed:
Intervertebral joints of the lumbar and thoracic vertebrae

Actions:

• bends the torso forwards (flexion)
• tilts the pelvis backwards (posterior tilt)

Origin:
Pubis

Insertion:
Cartilage of fifth, sixth and seventh ribs, and base of sternum