POSTERIOR ABDOMINAL WALL
The posterior abdominal wall is a complex region of anatomy. It is formed by the lumbar
vertebrae, pelvic girdle, posterior abdominal muscles and their associated fascia. Major
vessels, nerves and organs are located on the inner surface of the posterior abdominal
wall.
In this lecture, we shall look at the anatomy of the posterior abdominal wall – including
muscles, fascial layers and clinical correlations
Posterior Abdominal Muscles
There are five muscles in the posterior abdominal wall: the iliacus, psoas major, psoas
minor, quadratus lumborum and the diaphragm. We shall look at the attachments,
actions and innervation of these muscles in more detail.
Quadratus Lumborum
The quadratus lumborum muscle is located laterally in the posterior abdominal wall. It is
a thick muscular sheet which is quadrilateral in shape. The muscle is located posterior
to the psoas major.
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.
By TeachMeSeries Ltd (2026)
, Fig 1
The quadratus lumborum of the posterior abdominal wall.
Psoas Major
The psoas major is located near the midline of the posterior abdominal wall,
immediately lateral to the lumbar vertebrae.
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.
The posterior abdominal wall is a complex region of anatomy. It is formed by the lumbar
vertebrae, pelvic girdle, posterior abdominal muscles and their associated fascia. Major
vessels, nerves and organs are located on the inner surface of the posterior abdominal
wall.
In this lecture, we shall look at the anatomy of the posterior abdominal wall – including
muscles, fascial layers and clinical correlations
Posterior Abdominal Muscles
There are five muscles in the posterior abdominal wall: the iliacus, psoas major, psoas
minor, quadratus lumborum and the diaphragm. We shall look at the attachments,
actions and innervation of these muscles in more detail.
Quadratus Lumborum
The quadratus lumborum muscle is located laterally in the posterior abdominal wall. It is
a thick muscular sheet which is quadrilateral in shape. The muscle is located posterior
to the psoas major.
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.
By TeachMeSeries Ltd (2026)
, Fig 1
The quadratus lumborum of the posterior abdominal wall.
Psoas Major
The psoas major is located near the midline of the posterior abdominal wall,
immediately lateral to the lumbar vertebrae.
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.
