Abdominal and Pelvic Muscles

Question 1

External obliques
* Origin
* Insertion
* Action

Answer 1

• Origin: Ribs 5-12 and sternum
• Insertion: Iliac crest, inguinal ligament, linea alba, pubic tubercle
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• Action:

Bilaterally: anterior flexion of the trunk and compression of the abdomen

Unilaterally: lateral flexion of the trunk and rotation to the opposite side

Posterior tilt with pelvis and rotation

can help move pelvis independetly of trunk at the lumbosacral joint

Question 2

Internal obliques
* Origin
* Insertion
* Action

Answer 2

• Origin: Iliac crest, Inguinal ligament,
  thoracolumbar fascia
• Insertion: Ribs 10-12, pectineal line, linea alba, abdominal aponeurosis (fuses with external oblique to become the rectus sheath)
• ICILTF, RPLLAA
• Action:

Bilaterally: anterior flexion of the trunk and compression of
the abdomen

Unilaterally: lateral flexion of the trunk and rotation to the same side

Other than its unilateral action, the internal obliques are synergistic with the external obliques

Question 3

Transverse abdominis
* Origin
* Insertion
* Action

Answer 3

• Origin: Iliac crest, thoracolumbar fascia, Costal cartilage of ribs 7-12
• Insertion: Abdominal aponeurosis (and other midline structures)
• Action: Compression and tension of abdominal wall. provides stability of the trunk. and generating internal abdominal pressure (coughing)

functionally links thoracolumbar fascia (posteriorly) to the abdominal aponeurosis (anteriorly)

aka corset muscle

Question 4

Rectus abdominis
* Origin
* Insertion
* Action

Answer 4

• Origin: Pubic crest, tubercle and symphysis
• Insertion: Costal cartilages 5-7, Xiphoid process
• Action: Flexion of trunk

Question 5

Quadratus lumborum
* Origin
* Insertion
* Action

Answer 5

• Origin: Iliac crest
• Insertion: Transverse processes L1-L5; rib 12
• Action:
  Bilaterally: Extension of the trunk - but likely primarily contributes to stability of lumbar spine

Unilaterally: lateral flexion

primarily contributes to stability though in lateral flexion and extension (since role in trunk and flexion is small)

Helps with pelvic stability

Question 6

Puborectalis
* Origin
* Insertion
* Action

Answer 6

• Origin: anteriorly, from the pubic symphysis
• Insertion: posteriorly, encircling the anorectal junction (integrating in part with the external anal sphincter)
• Action: inhibits defecation and farting; also helps with defecation

consequences if damaged: uncontrolled defecation and farting

Question 7

Pubococcygeus
* Origin
* Insertion
* Action

Answer 7

• Origin: pubic bone (lateral to the origin of puborectalis)
• Insertion: Coccyx
• Action: Control urine flow; contract during orgasm

Question 8

Iliococcygeus
* Origin
* Insertion
* Action

Answer 8

• Origin: pubic bone (lateral to the origin of puborectalis)
• Insertion: Coccyx
• Action: Control urine flow; contract during orgasm