Posterior Abdominal Wall - Anatomy Flashcards
What are the 5 muscles of the posterior abdominal wall?
- Quadratus lumborum
- Psoas major
- Psoas minor
- Iliacus
- Diaphragm
Describe the quadratus lumborum
Located laterally in the posterior abdominal wall.
It is a thick muscular sheet which is quadrilateral in shape.
The muscle is positioned superficially to the psoas major.
Where does the quadratus lumborum originate from?
From the iliac crest and iliolumbar ligament.
How do the fibres of the quadratus lumborum travel? Where do they insert into?
The fibres travel superomedially, inserting onto the transverse processes of L1 – L4 and the inferior border of the 12th rib.
What are the actions of the quadratus lumborum?
Extension and lateral flexion of the vertebral column (antagonist to rectus abdominis)
How does the quadratus lumborus act during inspiration?
Fixes the 12th rib during inspiration, so that the contraction of diaphragm is not wasted.
What is the quadratus lumborus innervated by?
Anterior rami of T12-L4 nerves
Where is the psoas major located?
Located near the midline of the posterior abdominal wall, immediately lateral to the lumbar vertebrae.
Where does the psoas major originate from? Where does it attach to?
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.
What are the actions of the psoas major?
Flexion of the thigh at the hip and lateral flexion of the vertebral column.
What is the psoas major innervated by?
Anterior rami of L1 – L3 nerves
Where is the psoas minor located?
Anterior to the psoas major.
Where does the psoas minor originate from?
Vertebral bodies of T12 and L1
Where does the psoas minor attach to?
Attaches to a ridge on the superior ramus of the pubic bone, known as the pectineal line
What are the actions of the psoas minor?
Flexion of the vertebral column
What is the psoas minor innervated by?
Anterior rami of L1 spinal nerve
Where is the iliacus muscle located? What does it combine with?
Situated inferiorly on the posterior abdominal wall.
It combines with the psoas major to form the iliopsoas – the major flexor of the thigh.
Where does the iliacus muscle originate from?
Originates from surface of the iliac fossa and anterior inferior iliac spine
Where does the iliacus muscle insert? What do its fibres combine with before?
Its fibres combine with the tendon of the psoas major
Inserts into the lesser trochanter of the femur.
What are the actions of the iliacus muscle?
Flexion of the thigh at the hip joint.
What is the innervation of the iliacus muscle?
Femoral nerve (L2 – L4).
Which part of the diaphragm is considered to be part of the posterior abdominal wall?
The posterior aspect of the diaphragm
What is the psoas sign?
A medical sign that indicates irritation to the iliopsoas group of muscles
What is the psoas sign elicited by?
Flexion of the thigh at the hip.
The test is positive if the patient reports lower abdominal pain.
What lies between the parietal peritoneum and the muscles of the posterior abdominal wall?
A layer of fascia (sheet of connective tissue)
What is this layer of fascia between the parietal peritoneum and the muscles of the posterior abdominal wall continuous with?
The transversalis fascia of the anterolateral abdominal wall.
What should be noted about the fascia and its naming?
Whilst the fascia is one continuous sheet, it is anatomically correct to name the fascia according to the structure it overlies.
Where is the psoas fascia?
Covers the psoas major muscle
Where is the psoas fascia attached to?
It is attached to the lumbar vertebrae medially, continuous with the thoracolumbar fascia laterally and continuous with the iliac fascia inferiorly
What does the thoracolumbar fascia consist of?
Three layers; posterior, middle and anterior
What muscles are enclosed between the layers of the thoracolumbar fascia?
- Quadratus lumborum - between the anterior and middle layers.
- Deep back muscles - between the middle and posterior layers.
Where does the posterior layer of the thoracolumbar fascia extend between?
Between the 12th rib and the iliac crest posteriorly.
What does the thoracolumbar fascia meet laterally? What does it cover as it forms these attachments?
The internal oblique and transversus abdominis muscles, but not the external oblique.
The latissimus dorsi
What is the latissimus dorsi?
The largest muscle in the upper bod
What does the anterior layer of the thoracolumbar fascia attach me?
The anterior layer attaches to the anterior aspect of the transverse processes of the lumbar vertebrae, the 12th rib and the iliac crest
