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Questions and Answers
What is the main sensory function of the femoral nerve?
Which nerve is responsible for the cremasteric reflex?
What nerve is primarily responsible for the motor supply to the quadriceps femoris?
The LS trunk is formed by which segments coming together?
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Which muscle does the ilioinguinal nerve pierce before emerging at the superficial inguinal ring?
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What is the primary function of the lateral femoral cutaneous nerve?
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What is the primary blood supply to the colon?
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Which dermatome is likely to refer pain experienced in the L4-5 facet joint?
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Which branch of the genitofemoral nerve supplies the skin to the upper part of the femoral triangle?
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Which nerve is associated with innervating the obturator externus muscle?
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What causes engorged paraumbilical veins, a condition known as caput medusa?
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Where does the iliohypogastric nerve arise in relation to the psoas major?
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Which of the following structures does the lower thoracic sympathetic chain influence?
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Which nerve may also innervate pectineus when the femoral nerve does not?
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Which arteries branch off the abdominal aorta to supply the iliac region?
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What is the primary function of the pudendal nerve?
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Which muscles are primarily involved in flexing the hip joint?
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What anatomical structure does the Quadratus Lumborum muscle fix during inspiration?
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Which of the following nerves innervates the Iliacus muscle?
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Which plexus is formed by the ventral rami of L1 through L4?
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What is the primary function of the Psoas Minor muscle?
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Which branch of the lumbar plexus innervates the Quadratus Lumborum muscle?
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What is meant by caput medusa?
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Which lumbar vertebrae are involved in the innervation of the Psoas Major muscle?
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Which statement describes an incorrect function of the Psoas Major muscle?
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What role do lumbar ventral rami play in the lumbar plexus?
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Study Notes
Posterior Abdominal Wall
- Comprised of the lumbar vertebrae, sacrum, ilium, posterior aspect of the diaphragm, psoas major, iliacus muscles, and quadratus lumborum.
Quadratus Lumborum (QL) Muscle
- Originates from the medial half of the inferior border of rib 12 and the tips of the lumbar transverse processes.
- Inserts into the iliolumbar ligament and the internal lip of the iliac crest.
- Innervation: ventral rami T12, L1-L4.
- Actions:
- Fixes the 12th rib during inspiration.
- With the pelvis fixed, creates ipsilateral side bending of the vertebral column.
- Bilaterally, may assist in lumbar extension.
- Ipsilaterally, elevates the pelvis (hip hiker).
Psoas Major Muscle
- Originates from the transverse processes of all lumbar vertebrae, lateral aspect of the bodies of TV12 and lumbar vertebrae, and discs in between.
- Inserts into the lesser trochanter of the femur.
- Innervation: L2-L4 ventral rami.
- Actions:
- Flexes the hip joint.
- Side bends the vertebral column if the lower extremity is fixed.
- Flexes the trunk if the pelvis is fixed.
Psoas Minor Muscle
- Originates from the lateral aspect of TV12-LV1, and the discs in between.
- Inserts into the pectineal line and iliopectineal eminence.
- Innervation: L1 & L2 ventral ramus.
- Action: Assists in hip flexion and hip stabilization.
Iliacus Muscle
- Originates from the iliac crest, iliac fossa, ala of sacrum, and anterior sacroiliac ligaments.
- Inserts into the tendon of the psoas major, lesser trochanter, and femur just distal to it.
- Innervation: Femoral Nerve (L2-L3).
- Actions:
- Acts with the psoas major to flex the thigh at the hip.
- Stabilizes the hip joint.
Lumbar Ventral Rami
- Descend laterally in the psoas major muscle.
- L1, L2, L3, and most of L4 form the lumbar plexus.
- Part of L4 and all of L5 form the lumbosacral trunk, which joins the sacral plexus.
- L1 also receives a branch from T12 ventral rami (subcostal nerve).
Lumbar Plexus Branches
-
Muscular Branches: (T12), L1, L2, L3, L4 supply the following:
- Quadratus Lumborum (T12-L4).
- Psoas Minor (L1-L2).
- Psoas Major (L2-L3-L4).
- Iliacus (L2-L3).
-
Sensory Branches:
-
Iliohypogastric Nerve (L1):
- Arises from the upper border of the psoas major.
- Crosses the quadratus lumborum.
- Travels between the transversus abdominus and internal oblique muscles.
- Gives off a lateral cutaneous branch which supplies the posterolateral gluteal skin.
- Gives off an anterior cutaneous branch which supplies the suprapubic region.
-
Ilioinguinal Nerve (L1):
- Arises from the lateral border of the psoas major, caudal to the iliohypogastric nerve.
- Crosses the quadratus lumborum muscle.
- Often runs parallel to the border of the iliac crest.
- Pierces the transversus abdominus, runs between the transversus abdominus and internal oblique muscles.
- Emerges with the spermatic cord from the superficial inguinal ring.
- Supplies the proximomedial skin of the thigh.
-
Genitofemoral Nerve (L1, L2):
- Ascends obliquely forward through the psoas major muscle.
- Emerges near its medial border.
- Divides variably above the inguinal ligament into genital and femoral branches.
- Genital Branch: supplies the cremaster and scrotal skin.
- Femoral Branch: supplies the skin to the upper part of the femoral triangle.
-
Lateral Femoral Cutaneous Nerve (L2, L3):
- Emerges from the lateral border of the psoas major.
- Crosses the iliacus muscle obliquely.
- Passes deep to the inguinal ligament and divides into anterior and posterior branches.
- Anterior Branch: supplies the skin of the anterior and lateral thigh to the knee.
- Posterior Branch: supplies the skin of the lateral surface from the greater trochanter to the mid-thigh.
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Obturator Nerve (L2, L3, L4) - Motor and Sensory Responsibilities:
- Descends in the psoas major.
- Emerges on its medial border at the pelvic brim.
- Descends forward on the pelvic wall.
- Near the obturator foramen, divides into anterior and posterior branches.
- Passes through the obturator foramen.
- Anterior Branch: innervates the hip joint, adductor longus, gracilis, usually adductor brevis, sometimes pectineus (when not innervated by the femoral nerve), and the skin of the medial thigh.
- Posterior Branch: innervates the obturator externus and the adductor portion of adductor magnus.
- Sensory: medial aspect of the thigh.
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Femoral Nerve (L2, L3, L4) - Motor and Sensory Responsibilities:
- Descends through the psoas major.
- Emerges on its lateral border.
- Gives off motor branches to the iliacus (in the abdomen) and pectineus (from the medial side of the nerve).
- Motor Branches: supplies the iliacus, pectineus, sartorius, quadriceps femoris (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius), and the articular branches to the knee joint.
- Sensory Branches: supplies the anterior thigh, medial thigh, and the skin over the patella, as well as the medial malleolus.
-
Iliohypogastric Nerve (L1):
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Description
Explore the anatomy of the posterior abdominal wall, including key muscles such as the quadratus lumborum and psoas major. Understand their origins, insertions, innervations, and functions. This quiz will test your knowledge on the structure and actions of these essential muscles.
