Internal and External Obliques Anatomy: Origin, Insertion, Action and Innervation

Obliques Anatomy Study

Obliques Anatomy - Internal

Internal Oblique

Origin: Lumbar fascia, anterior two-thirds of the iliac crest, and the lateral two-thirds of the inguinal ligament
Insertion: Costal margin, aponeurosis of the rectus sheath, conjoined tendon to the pubic crest and pectineal line, 10-12 rib
Action: Compresses abdomen; unilateral contraction rotates vertebral column to same side
Innervation: Ventral Primary rami of (T6 to T12, L1)
Blood Supply: Muscular branches from the superior and inferior epigastric and deep circumflex iliac arteries

Synergist: Diaphragm, External oblique abdominis, Transverse abdominis, Rectus abdominis, Pyramidalis, Levator Ani

Primary Actions of the Internal Obliques:

1. Lateral flexion of the thoracic spine when acting unilaterally

  • Agonists: Iliocostalis cervicis, thoracis and lumborum Longissimus cervicis and thoracis, External oblique
  • Antagonists: Iliocostalis cervicis,  thoracics, and lumborum, Longissimus cervicis and thoracics, External oblique on the opposite side

2. Lateral flexion of the lumbar spine when acting unilaterally

  • Agonists: Iliocostalis lumborum, Longissimus thoracis, Psoas Major, Quadratus lumborum, External Oblique
  • Antagonists: Iliocostalis lumborum, Longissimus thoracis, Psoas Major, Quadratus lumborum, External Oblique on the opposite side

3. Ipsilateral rotation of the trunk when acting unilaterally

Secondary Actions of the Internal Obliques:

1. Assists with flexion of the thoracic spine when acting bilaterally

  • Agonists: Rectus abdominis
  • Antagonists: Iliocostalis cervicis, thoracis and lumborum Longissimus cervicis and thoracis, Spinalis thoracis, Semispinalis cervicis and thoracis

2. Assists with flexion of the lumbar spine when acting bilaterally

  • Agonists: Rectus Abdominis
  • Antagonists: Iliocostalis lumborum, Longissimus thoracis, Spinalis thoracis

3. Assists with forced expiration

  • Agonists: Serratus posterior inferior, Transversus abdominis
  • Antagonists:Serratus posterior superior, Levatores costarum breves and longi




Obliques Anatomy - External

External Obliques

Origin: Anterior fibers: external surfaces of ribs 5 to 8, interdigitating with serratus anterior. Lateral fibers: external surfaces of 9th rib, interdigitating serratus anterior, and those ribs 10 to 12, interdigitating with lattissimus dorsi.
Insertion:  Anterior Fibers: into a broad flat aponeurosis, terminating at the linea alba.
Lateral fibers: into the anterior iliac spine and pubic tubercle, and into the external lip of the anterior half of the iliac crest.
Action: Flexion and rotation of the spine
Innervation: Ventral primary rami of T7 to T12
Blood Supply: Branches from the musculophrenic artery, the lower two or three posterior intercostal arteries,  the subcostal artery, and branches of the superficial epigastric artery

Synergists: Internal oblique, Diaphragm,  Transverse abdominis, Rectus abdominis, Pyramidalis, Levator Ani

Primary Actions of the External Obliques:

1. Lateral flexion of the thoracic spine when acting unilaterally

  • Agonists: Iliocostalis cervicis, thoracis and lumborum Longissimus cervicis and thoracis, Internal oblique
  • Antagonists: Iliocostalis cervicis,  thoracics, and lumborum, Longissimus cervicis and thoracics, External oblique on the opposite side

2. Contralateral rotation of the lumbar spine when acting unilaterally

  • Agonists: Semispinalis cervicis and thoracis, Multifidus
  • Antagonists: Semispinalis cervicis and thoracis, Multifidus on the opposite side

3. Lateral flexion of the spine when acting unilaterally

  • Agonists: Iliocostalis lumborum, Longissimus thoracis, Psoas major, Quadratus lumborum, Internal oblique
  • Antagonists:Iliocostalis lumborum, Longissimus thoracis, Psoas major, Quadratus lumborum, Internal oblique on opposite side

Secondary Actions of the External Obliques:

1. Assists with flexion of the thoracic spine when acting bilaterally

  • Agonists: Rectus abdominis
  • Antagonists: Iliocostalis cervicis, thoracis and lumborum Longissimus cervicis and thoracis, Spinalis thoracis, Semispinalis cervicis and thoracis

2. Assists with flexion of the lumbar spine when acting bilaterally

  • Agonists: Rectus Abdominis
  • Antagonists: Iliocostalis lumborum, Longissimus thoracis, Spinalis thoracis

3. Supports the abdominal wall

  • Agonists: Rectus abdominis
  • Antagonists: None

4. Assists with forced expiration

  • Agonists: Serratus posterior inferior, Transversus abdominis
  • Antagonists:Serratus posterior superior, Levatores costarum breves and longi

For more information see: External and Internal Obliques Muscles: Waist, Low Abdomen, Heartburn,Groin, Testicular Pain


Learn Human Anatomy

coloring_book
The Anatomy Coloring Book is one of the best study and reference books for beginning anatomy students. The diagrams are clearly labeled and allow you to see the relationship and placement of the various structures of the body. You will also be surprised how the act of coloring will help with recall. But this is not just a beginners book, it is also great for practitioners and therapists to have on hand to use with clients and patients to use as a visual reference.


References:

The Trigger Point Therapy Workbook – Claire Davies, Amber Davies, and David G. Simons

Basic Clinical Massage Therapy: Integrating Anatomy and Treatment – James H. Clay and David M. Pounds

Trigger Point Therapy for Myofascial Pain – Donna Finando and Steven Finando

 



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