Abdominal Wall Muscles

Question 1

What are the anterolateral muscles?

Answer 1

External oblique
Internal oblique
Transversalis abdominis

Question 2

Outline the external oblique muscle
- origin
- insertion
- innervation
- action

Answer 2

‘Hands in pockets’
- Origin: external surface of 5th-12th rib
- Insertion: iliac crest, linea alba, pubic tubercle
- Innervation: T7-T12
- Action: ~ bilateral contraction -compress abdominal viscera, flex trunk + expiration ~ unilateral contraction - rotation of trunk to opposite side

Question 3

Outline the internal oblique muscle
- origin
- insertion
- innervation
- action

Answer 3

• Origin: lateral portion of inguinal ligament, iliac crest, thoracolumbar fascia
• Insertion: linea alba via aponeurosis, pubic crest + 10-12th ribs
• Innervation: T7-L1
• Action: ~ bilateral contraction -compress abdominal viscera, flex trunk + expiration ~ unilateral contraction - rotation of trunk to same side

Question 4

Outline the transversalis abdominus muscle
- origin
- insertion
- innervation
- action

Answer 4

• Origin: 7th-12th rib + thoracolumbar fascia
• Insertion: linea alba + pubic crest
• Innervation: T7-L1
• Action: ~ bilateral contraction: expiration + compress abdominal viscera > core stability

Question 5

Outline the Rectus abdominus muscle
- origin
- insertion
- innervation
- action

Answer 5

• Origin: pubic crest, pubic tubercle, pubic symphysis
• Insertion: costal cartilage of 5th-7th ribs + xiphoid process
• Innervation: T7-T12
• Action: compress abdominal viscera, flex trunk + expiration

Question 6

What is the Rectus sheath?

Answer 6

The aponeurosis of the lateral muscles surrounding the Rectus abdominus

Question 7

What is the arcuate line?

Answer 7

• Lower limit of the posterior layer of Rectus sheath
• Roughly halfway between umbilicus and pubic crest

Question 8

Describe the rectus sheath above + below the arcuate line

Answer 8

• above: formed by all 3 aponeuroses (EO,IO+TA) enclosing Rectus abdominis
• below: only formed by aponeurosis of EO + anterior layer of IO | TA aponeuroses blens into posterior layer of IO
• sheath is thinner below the arcuate line

Question 9

Describe the rectus sheath above the arcuate line

Answer 9

Formed by all three aponeuroses
- external oblique
- internal oblique
- transversus abdominius

Question 10

Describe rectus sheath below the arcuate line

Answer 10

• Only formed by aponeuroses of external oblique + anteior alter of internal oblique
• posterior layer of internal oblique blends into transversus abdominis aponeurosis