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Questions and Answers
What is the primary action of the quadratus lumborum when both sides are contracted?
Which nerves supply the iliacus muscle?
Which muscles share the action of flexing the thigh?
What is the location of the lumbar plexus in relation to the psoas major?
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Which of the following muscles may be absent in some individuals?
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What is the origin of the quadratus lumborum muscle?
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Which nerve is responsible for innervating the obturator muscle?
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What is a potential complication of a TB infection in the vertebral column?
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Which of the following does NOT contribute to the formation of the lumbar plexus?
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What is the insertion point for the psoas major muscle?
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What is the unilateral action of the quadratus lumborum muscle?
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Which nerve supplies the psoas major muscle?
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What is the action of the iliacus muscle when it contracts?
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Which of the following is the insertion point for the iliacus muscle?
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Which structures are formed by the branches of the lumbar plexus?
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What is the correct relation of the genitofemoral nerve to the psoas major?
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Which of the following describes the bilateral action of the psoas major?
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Where does the psoas minor insert?
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What is the action associated with the psoas minor?
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Which nerves are responsible for innervating the femoral nerve?
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Study Notes
Quadratus Lumborum
- Originates from the iliac crest and ilio-lumbar ligament.
- Inserts on the transverse processes of the upper four lumbar vertebrae and the last rib.
- Innervated by the subcostal nerve and upper three or four lumbar nerves.
- Actions include unilateral lateral flexion of the trunk and bilateral trunk extension.
Iliacus
- Arises from the iliac fossa and ala of the sacrum.
- Inserts at the lesser trochanter of the femur.
- Innervated by the femoral nerve.
- Function is to flex the thigh.
Psoas Major
- Originates from the body of T12, all lumbar vertebrae, and intervertebral discs.
- Inserts at the lesser trochanter of the femur.
- Supplied by the upper three lumbar nerves.
- Works with iliacus to flex the thigh, laterally flexes the trunk unilaterally, and flexes the trunk bilaterally.
Psoas Minor
- May be absent; originates from the body of T12 and L1.
- Inserts at the ilio-pubic eminence.
- Innervated by L1.
- Provides weak flexion of the trunk.
Psoas Abscess
- Tuberculosis infection of the vertebral column may lead to a psoas abscess within the psoas sheath.
- Pus from the psoas abscess can spread down the thigh through the psoas sheath.
Lumbar Plexus
- Located inside the psoas major.
- Formed by the ventral rami of the upper four lumbar nerves.
- Branch arrangements:
- L1 gives rise to iliohypogastric and ilioinguinal nerves.
- L1 and L2 combine to form the genitofemoral nerve.
- L2 and L3 form the lateral cutaneous nerve (LCN) of the thigh.
- L2, L3, and L4 divide into anterior and posterior divisions, which give rise to the obturator nerve (anterior) and femoral nerve (posterior).
- L3 and L4 contribute to the obturator accessory nerve.
Relations to Psoas Major
- Lateral to psoas major: iliohypogastric, ilioinguinal, LCN of the thigh, and femoral nerve.
- Anterior to psoas major: genitofemoral nerve.
- Medial to psoas major: obturator nerve and obturator accessory nerve.
Quadratus Lumborum
- Originates from the iliac crest and ilio-lumbar ligament.
- Inserts on the transverse processes of the upper four lumbar vertebrae and the last rib.
- Innervated by the subcostal nerve and upper three or four lumbar nerves.
- Actions include unilateral lateral flexion of the trunk and bilateral trunk extension.
Iliacus
- Arises from the iliac fossa and ala of the sacrum.
- Inserts at the lesser trochanter of the femur.
- Innervated by the femoral nerve.
- Function is to flex the thigh.
Psoas Major
- Originates from the body of T12, all lumbar vertebrae, and intervertebral discs.
- Inserts at the lesser trochanter of the femur.
- Supplied by the upper three lumbar nerves.
- Works with iliacus to flex the thigh, laterally flexes the trunk unilaterally, and flexes the trunk bilaterally.
Psoas Minor
- May be absent; originates from the body of T12 and L1.
- Inserts at the ilio-pubic eminence.
- Innervated by L1.
- Provides weak flexion of the trunk.
Psoas Abscess
- Tuberculosis infection of the vertebral column may lead to a psoas abscess within the psoas sheath.
- Pus from the psoas abscess can spread down the thigh through the psoas sheath.
Lumbar Plexus
- Located inside the psoas major.
- Formed by the ventral rami of the upper four lumbar nerves.
- Branch arrangements:
- L1 gives rise to iliohypogastric and ilioinguinal nerves.
- L1 and L2 combine to form the genitofemoral nerve.
- L2 and L3 form the lateral cutaneous nerve (LCN) of the thigh.
- L2, L3, and L4 divide into anterior and posterior divisions, which give rise to the obturator nerve (anterior) and femoral nerve (posterior).
- L3 and L4 contribute to the obturator accessory nerve.
Relations to Psoas Major
- Lateral to psoas major: iliohypogastric, ilioinguinal, LCN of the thigh, and femoral nerve.
- Anterior to psoas major: genitofemoral nerve.
- Medial to psoas major: obturator nerve and obturator accessory nerve.
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Description
This quiz covers the anatomy of the posterior abdominal wall, focusing on the Quadratus Lumborum and Iliacus muscles. Key aspects include their origins, insertions, nerve supply, and actions. Test your knowledge on these important muscles and their role in trunk movement.
