Podcast
Questions and Answers
What is the action of the rectus abdominus muscle?
What is the action of the rectus abdominus muscle?
What is the origin of the external oblique muscle?
What is the origin of the external oblique muscle?
External surfaces of ribs 5-12
What is the insertion point of the transversus abdominus muscle?
What is the insertion point of the transversus abdominus muscle?
Linea alba with aponeurosis of internal oblique, pubic crest and pectin pubis via conjoint tendon
What nerve innervates the iliacus muscle?
What nerve innervates the iliacus muscle?
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The psoas major muscle acts to flex the vertebral column laterally.
The psoas major muscle acts to flex the vertebral column laterally.
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The action of the internal oblique muscle is to ______ and ______ the trunk.
The action of the internal oblique muscle is to ______ and ______ the trunk.
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What is a key function of the quadratus lumborum muscle?
What is a key function of the quadratus lumborum muscle?
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What is found below the arcuate line in the abdominal wall?
What is found below the arcuate line in the abdominal wall?
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Study Notes
Muscular Layers of the Anterior Abdominal Wall
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External Oblique
- Origin: External surfaces of ribs 5-12
- Insertion: Linea alba, pubic tubercle, anterior half of iliac crest
- Action: Compresses and supports abdominal viscera; flexes and rotates the trunk
- Innervation: Thoraco-abdominal nerves (T7-T11) and subcostal nerve (T12)
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Internal Oblique
- Origin: Thoracolumbar fascia, anterior 2/3 of iliac crest, connective tissue deep to inguinal ligament
- Insertion: Inferior borders of ribs 10-12, linea alba, pubis via conjoint tendon
- Action: Compresses and supports abdominal viscera; flexes and rotates the trunk
- Innervation: Thoraco-abdominal nerves (T7-T11) and first lumbar nerve (L1)
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Rectus Abdominus
- Origin: Pubic symphysis and pubic crest
- Insertion: Xiphoid process and costal cartilages 5-7
- Action: Flexes trunk and compresses abdominal viscera; stabilizes pelvic tilt
- Innervation: Thoraco-abdominal nerves (inferior six thoracic nerves)
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Transversus Abdominus
- Origin: Internal surfaces of ribs 7-12, thoracolumbar fascia, iliac crest, connective tissue deep to inguinal ligament
- Insertion: Linea alba (with internal oblique aponeurosis), pubic crest, pectin pubis via conjoint tendon
- Action: Compresses and supports abdominal viscera
- Innervation: Thoraco-abdominal nerves (T7-T11) and first lumbar nerve (L1)
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Arcuate Line Significance
- Above the arcuate line, muscle tendons split around rectus abdominus, creating posterior support.
- Below the arcuate line, tendons fuse anteriorly, leaving transversalis fascia and parietal peritoneum, making this area weaker and prone to hernias.
Posterior Abdominal Wall Musculature
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Psoas Major
- Origin: Transverse processes of lumbar vertebrae and sides of T12-S1 vertebral bodies
- Insertion: Lesser trochanter of femur
- Action: Flexes thigh (inferiorly); flexes vertebral column laterally to balance trunk (superiorly)
- Innervation: Anterior rami of lumbar nerves L1-L3
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Psoas Minor
- Origin: Sides of T12-L1 vertebral bodies
- Insertion: Pectineal line and iliopubic eminence
- Action: Weak trunk flexor
- Innervation: L1
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Iliacus
- Origin: Superior two-thirds of iliac fossa, ala of sacrum, anterior sacro-iliac ligaments
- Insertion: Lesser trochanter of femur and shaft inferior to it
- Action: Flexes thigh and stabilizes hip joint; works with psoas major
- Innervation: Femoral nerve (L2-L4)
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Quadratus Lumborum
- Origin: Medial half of the inferior border of the 12th rib and tips of lumbar transverse processes
- Insertion: Iliolumbar ligament and internal lip of iliac crest
- Action: Extends and laterally flexes vertebral column; fixes 12th rib during inspiration
- Innervation: Anterior branches of T12 and L1-L4 nerves
Formative Assessment
- Examining the action of the rectus abdominus reveals it flexes the trunk and compresses abdominal viscera.
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Description
This quiz focuses on the muscular layers of the abdominal wall as outlined in Units 2.12 and 2.13 of the OT Anatomy lecture. It covers key aspects such as origins, insertions, innervations, and actions, along with an understanding of the rectus sheath. Prepare to test your knowledge and comprehension of the abdominal anatomy as presented in the specified reading material.
