Abdominal MM

Question 1

What are the 2 groups of muscles in the abdominal region?

Answer 1

Anterolateral

• rectus abdominus
• pyramidalis (sometimes present)
• external oblique
• internal oblique
• transverse abdominus

Posterior:
- quadratus lumborum
- psoas major
- psoas minor
- iliacus
(posterior attachments of diaphragm are sometimes included)

Question 2

What are the 2 types of muscles in the anterolateral abdominal wall?

Answer 2

Vertical

• rectus abdominus
• pyramidalis (sometimes present)

Flat:

• external oblique
• internal oblique
• transverse abdominus

Question 3

Describe the flat anterolateral abdominal muscles

Answer 3

External oblique
(superficial layer)
PA: external surface of ribs 5-12
DA: linea alba, pubic tubercle, and anterior half of iliac crest
NS: thoracoabdominal nerve (from ventral rami of inferior 6 thoracic nerves) and subcostal nerve
A: trunk flexion, contralateral trunk rotation, compression and support of abdominal viscera

Internal oblique
(middle layer)
PA: thoracolumbar fascia, anterior two thirds of iliac crest, and lateral half of inguinal ligament
DA: inferior borders of ribs 10-12, linea alba, pectineal line via conjoint tendon
NS: thoracoabdominal nerves (from ventral rami of inferior 6 thoracic nerves) and first lumbar spinal nerve
A: trunk flexion, ipsilateral trunk rotation, compression and support of abdominal viscera

Transverse abdominus
(deep layer)
PA: thoracolumbar fascia, iliac crest, lateral third of inguinal ligament, and inferior surfaces of costal cartilages 7-12
DA: linea alba, pubic crest, and pectineal line via conjoint tendon
NS: thoracoabdominal nerves (from ventral rami of inferior 6 thoracic nerves) and first lumbar spinal nerve
A: compression and support of abdominal viscera

Question 4

Which abdominal muscles receive innervation from the thoracoabdominal nerves?

Answer 4

The external oblique, internal oblique and transverse abdominus receive innervation from the thoracoabdominal nerves originating from the ventral rami of the inferior 6 thoracic spinal nerves.

The external oblique also receives innervation from the subcostal nerve.
The internal oblique and transverse abdominus also receive innervation from the L1 spinal nerve.

Question 5

Which abdominal muscles play a role in compressing and supporting the abdominal viscera?

Answer 5

The external oblique, internal oblique, transverse abdominus, and rectus abdominus

Question 6

Describe the rectus abdominus muscle

Answer 6

PA: pubic symphysis and pubic crest
DA: xiphoid process and costal cartilages 5-7
NS: thoracoabdominal nerves (from ventral rami of inferior 6 thoracic spinal nerves)
A: trunk flexion, compression and support of abdominal viscera

Question 7

Describe the fibre orientation of the anterolateral abdominal muscles

Answer 7

External oblique: fibres run inferomedially from the external surfaces of ribs 5-12 posteriorly to the linea alba, pubic tubercle and anterior half of the iliac crest anteriorly

Internal oblique: fibres run in different directions in different places. Superior the ASIS, fibres run obliquely upwards. At the level of the ASIS, fibres run horizontally. Inferior to the ASIS, fibres run obliquely downward. Fibres run from the thoracolumbar fascia, anterior two thirds of the iliac crest and lateral half of the inguinal ligament postero-laterally towards the inferior borders of ribs 10-12, linea alba and pectineal line antero-medially.

Transverse abdominus: most fibres run transversomedially. The inferior fibres run parallel to the fibres of the internal oblique. Fibres run from the thoracolumbar fascia, iliac crest, lateral third of the inguinal ligament and inferior surfaces of costal cartilages 7-12 posteriorly towrds the linea alba, pubic crest and pectineal line anteriorly.

Question 8

Which 2 anterolateral abdominal muscles have a proximal attachment to the thoracolumbar fascia?

Answer 8

The internal obliques, and the transverse abdominus

Question 9

Which 2 anterolateral abdominal muscles have a proximal attachment to the iliac crest?

Answer 9

The internal oblique (anterior two thirds of iliac crest), and the transverse abdominus (iliac crest)

Question 10

Which 2 anterolateral abdominal muscles have a proximal attachment to the ribs or costal cartilages?

Answer 10

The external oblique (external surfaces of ribs 5-12) and the transverse abdominus (inferior surfaces of costal cartilages 7-12)

Question 11

Which 2 anterolateral abdominal muscles have a distal attachment to the linea alba and pectineal line?

Answer 11

The internal oblique and the transverse abdominus

Question 12

Describe the 4 muscles of the posterior abdominal wall

Answer 12

Quadratus lumborum:
PA: iliac crests, iliolumbar ligament
DA: TPs of L1-4, inferior border rib 12
NS: ventral rami of T12-L4
A: extension and lateral flexion of spine, fixes rib 12 during inspiration

Psoas major:
PA: TPs of T12-L5
DA: lesser trochanter of femur (as iliopsoas)
NS: ventral rami of L1-3
A: flexion of the thigh and hip, lateral flexion of the spine

Psoas minor:
PA: T12-L1 vertebral bodies
DA: pectineal line of pubic bone
NS: ventral rami of L1
A: flexion of the lumbar spine

Iliacus:
PA: iliac fossa of the ilium, AIIS
DA: lesser trochanter of femur (as iliopsoas)
NS: femoral nerve (L2-4)
A: flexion of the thigh and hip