Abdominal wall muscles

Question 1

Rectus abdominis

Answer 1

Attachments:
Originates from the crest of the pubis bone. It inserts onto the xiphoid process of the sternum and the costal cartilage of ribs 5-7.

Actions:
As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs.

Innervation:
Thoracoabdominal nerves (T7-T11).

Blood supply:
Inferior and superior epigastric vessels

Question 2

External oblique

Answer 2

Attachments:
Originates from ribs 5-12 and inserts onto the iliac crest and pubic tubercle.

Actions:
Contralateral rotation of the torso.

Innervation:
Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12).

Blood supply:
Lower posterior intercostal arteries, subcostal artery, deep circumflex iliac artery

Question 3

Internal oblique

Answer 3

Attachments:
Originates from the inguinal ligament, iliac crest and lumbodorsal fascia. It inserts onto ribs 10-12.

Actions:
Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.

Innervation:
Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.

Blood supply:
Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries,posterior lumbar arteries

Question 4

Transversus abdominis

Answer 4

Attachments:
Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. It inserts onto the conjoint tendon, xiphoid process, linea alba and the pubic crest.

Actions:
Compression of abdominal contents.

Innervation:
Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.

Blood supply:
Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries,posterior lumbar arteries

Question 5

Pyramidalis

Answer 5

Attachments:
Originates from the pubic crest and pubic symphysis before inserting into the linea alba.

Actions:
Tenses the linea alba.

Innervation:
Subcostal nerve (T12).

Blood supply:
Inferior epigastric artery

Question 6

Quadratus lumborum

Answer 6

Attachments:
Originates from the iliac crest and iliolumbar ligament. The fibres travel superomedially, inserting onto the transverse processes of L1 – L4 and the inferior border of the 12th rib.

Actions:
Extension and lateral flexion of the vertebral column. It also fixes the 12th rib during inspiration, so that the contraction of diaphragm is more efficient.

Innervation: Anterior rami of T12 – L4 nerves.

Blood supply:
Lumbar, median sacral, iliolumbar and subcostal arteries

Question 7

Psoas major

Answer 7

Attachments:
Originates from the transverse processes and vertebral bodies of T12 – L5. It then moves inferiorly and laterally, running deep to the inguinal ligament, and attaching to the lesser trochanter of the femur.

Actions:
Flexion of the thigh at the hip and lateral flexion of the vertebral column.

Innervation:
Anterior rami of L1 – L3 nerves.

Blood supply:
Lumbar branch of iliolumbar artery

Question 8

Psoas minor

Answer 8

Attachments:
Originates from the vertebral bodies of T12 and L1 and attaches to a ridge on the superior ramus of the pubic bone, known as the pectineal line.

Actions:
Flexion of the vertebral column.

Innervation:
Anterior rami of the L1 spinal nerve.

Blood supply:
Lumbar arteries

Question 9

Iliacus

Answer 9

Attachments:
Originates from the surface of the iliac fossa and anterior inferior iliac spine. Its fibres combine with the tendon of the psoas major, inserting into the lesser trochanter of the femur.

Actions:
Flexion and lateral rotation of the thigh at the hip joint.

Innervation:
Femoral nerve (L2 – L4).

Blood supply:
liolumbar, deep circumflex iliac, obturator, and femoral arteries

Question 10

Diaphragm

Answer 10

Attachments:
Sternal part: Posterior aspect of xiphoid process
Costal part: Internal surfaces of lower costal cartilages and ribs 7-12
Lumbar part: Medial and lateral arcuate ligaments (lumbocostal arches), bodies of vertebrae L1-L3 (+intervertebral discs), anterior longitudinal ligament
Inserting on to the Central tendon of diaphragm

Actions:
Depresses costal cartilages, primary muscle of breathing (inspiration)

Innervation:
Phrenic nerves (C3-C5)

Blood supply:
Subcostal and lowest 5 intercostal arteries, inferior phrenic arteries, superior phrenic arteries

Openings: vena cava has eight letters (T8), oesophagus has ten letters (T10), and aortic hiatus has twelve letters (T12)