1.2 Muscles of the Anterior Abdominal Wall

Question 1

Name the 3 flat muscles of the anterolateral abdominal wall (superficial to deep)

Answer 1

1. External oblique
2. Internal oblique
3. Transversus abdominis

Question 2

What are the actions of the external oblique?

Answer 2

1. Compress & support abdominal viscera

2. Flex & rotate the trunk

Question 3

What are the actions of the internal oblique?

Answer 3

1. Compress & support abdominal viscera

2. Flex & rotate the trunk

Question 4

What is the action of the transversus abdominis?

Answer 4

Compresses and supports abdominal viscera

Question 5

What is the innervation of the external oblique?

Answer 5

Thoraco-abdominal nerves (anterior rami of T7-T11) and subcostal nerve

Question 6

What is the innervation of the internal oblique?

Answer 6

Thoraco-abdominal nerves (anterior rami of T7-T11), subcostal and first lumbar nerve

Question 7

What is the innervation of the transversus abdominis?

Answer 7

Thoraco-abdominal nerves (anterior rami of T7-T11), subcostal and first lumbar nerve

Question 8

Name the 2 vertical muscles of the anterolateral abdominal wall

Answer 8

1. Rectus abdominis

2. Pyramidalis (absent in about 20% of people)

Question 9

What are the actions of the rectus abdominis?

Answer 9

1. Flexes trunk (lumbar vertebrae) and compresses abdominal viscera
2. Stabilises and controls tilt of pelvis (antilordosis)

Question 10

What is the innervation of the rectus abdominis?

Answer 10

Thoraco-abdominal and subcostal nerves (anterior rami of T7-T12 spinal nerves)

Question 11

Superior to the umbilicus, where does the rectus abdominis lie?

Answer 11

Within the rectus sheath; E.O. aponeurosis in front; T.A. behind - I.O. aponeurosis splits

Question 12

Inferior to the umbilicus, where does the rectus abdominis lie?

Answer 12

Deep to the rectus sheath; aponeurosis of all 3 muscles goes in front

Question 13

What is the rectus sheath?

Answer 13

The aponeuroses of the external oblique, internal oblique and transverse abdominis muscles

Question 14

What is the pyramidalis muscle?

Answer 14

A small triangular muscle, that lies in the rectus sheath anterior to the inferior part of the rectus abdominis; it arises from the pubic crest and attaches along the lines alba, which it tenses (LA is white fibrous tissue between xiphoid process and pubic symphysis)

Question 15

What is an aponeurosis?

Answer 15

A sheet of pearly white fibrous tissue which takes the place of a tendon in sheet-like muscles having a wide area of attachment

Question 16

At what level is the umbilicus in the abdominal wall?

Answer 16

L3/L4

Question 17

Why is the umbilicus a good surface landmark?

Answer 17

It marks the bifurcation of the abdomen aorta

Question 18

Which thoracic spinal segments innervate the anterior abdominal wall?

Answer 18

T7-T12

Question 19

Which dermatome supplies the level of the umbilicus?

Answer 19

T10