Abdominal wall muscles

Question 1

External oblique

Answer 1

Origin:

• Muscluar slips from the outer surfaces of the lower eight ribs

Insertion:

• Lateral lip of iliac crest
• Aponeuroses ending in midline raphe (linea alba)

Innervation:

• Anterior rami of lower six thoracic spinal nerves

Function:

• Compress abdominal contents
• Both muscles flex trunk
• Each muscle bends trunk to same side
• Turning anterior part of abdomen to opposite side

Question 2

Internal oblique

Answer 2

Origin:

• Thoracolumbar fascia
• Iliac crest between origins of external and transversis
• Lateral two thrids of inguinal ligament

Insertion:

• Inferior border of the lower three or four ribs
• Aponeuroses ending in linea alba
• Pubic crest and pectineal line

Innervation:

• Anterior rami of lower six thoracic spinal nerves

Function:

• Compress abdominal contents
• Both muscles flex trunk
• Each muscle bends trunk
• Turns anterior part of abdomen to the same side

Question 3

Transversus abdominis

Answer 3

Origin:

• Thoracolumbar fascia
• Medial lip of iliac crest
• Lateral one third of inguinal ligament
• Costal cartilages of lower six ribs

Insertion:

• Aponeurosis ending in linea alba
• Pubic crest
• Pectineal line

Innervation:

• Anterior rami of lower six thoracic spinal nerves

Function:

• Compress abdominal contents

Question 4

Rectus abdominis

Answer 4

Origin:

• Pubic crest
• Pubic tubercle
• Pubic symphesis

Insertion:

• Costal cartilages of ribs 5 to 7
• Xiphoid process

Innervation:

• Anterior rami of lower seven thoracic spinal nerves

Function:

• Compress abdominal contents
• Flex vertebral column
• Tense abdominal wall

Question 5

Pyramidalis

Answer 5

Origin:

• Front of pubis
• Pubic symphesis

Insertion:

• Into linea alba

Innervation:

• Anterior ramus of T12

Function:

• Tenses the linea alba