Anterior Abdominal Wall Notes

Overview of the Anterior Abdominal Wall

• Provides stability and protection for the trunk

• Allows a range of movements to occur

Layers of the Anterior Abdominal Wall

• Superficial to Deep:

  • Skin

  • Subcutaneous fascia

  • Fatty layer: Camper’s fascia

  • Membranous layer: Scarpa’s fascia

  • Muscular layers:

  • External oblique

  • Internal oblique

  • Transversus abdominis

  • Transversalis fascia

  • Peritoneum

Muscles of the Anterolateral Abdominal Wall

• External Oblique:

  • Forms the outermost muscle layer

  • Attaches from the sternum to the inguinal ligament, and contributes to the rectus sheath

• Internal Oblique:

  • Located beneath the external oblique

  • also attaches to the ribcage and pelvis, assists in forming the rectus sheath

• Transversus Abdominis:

  • Innermost muscle layer

  • Runs horizontally, stabilizes the abdominal wall

• Rectus Abdominis:

  • Runs vertically along the front of the abdomen

  • Divided into sections by tendinous intersections

The Rectus Sheath

• Formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis

• Contains:

  • Epigastric arteries

  • Thoracoabdominal nerves (continuations of intercostal nerves)

• Varies above and below the umbilicus:

  • Above Umbilicus: All three aponeuroses form the sheath at the anterior rectus abdominis.

  • Below Umbilicus: The internal oblique and transversus abdominis descend to the posterior layer.

Blood Supply of the Abdominal Wall

• Main Arteries:

  • Subclavian artery → Internal thoracic artery → Superior epigastric artery

  • Common iliac artery → External iliac artery → Inferior epigastric artery

  • Femoral artery → Superficial epigastric artery

  • Also receives blood from posterior intercostals and subcostal arteries.

Nerve Supply of the Abdominal Wall

• Intercostal Nerves:

  • Continue into the anterior abdominal wall as thoracoabdominal nerves

  • Run between the internal oblique and transversus abdominis

  • Functions:

  • Sensory innervation to the skin over abdominal muscles

  • Somatic motor innervation to the abdominal wall muscles

  • Sensory innervation to the parietal peritoneum

The Inguinal Region

• Located in the inferior abdomen

• Key Structures:

  • Inguinal ligament (ASIS to pubic tubercle)

  • Inguinal canal (contains spermatic cord in males and round ligament of uterus in females)

Boundaries of the Inguinal Canal

• Anterior Wall:

  • External oblique aponeurosis medially

  • External and internal oblique muscle laterally

• Roof:

  • Internal oblique muscle

  • Transversus abdominis

  • Transversalis fascia

• Posterior Wall:

  • Transversalis fascia & conjoint tendon medially

  • Transversalis fascia laterally

• Floor:

  • Inguinal ligament

Contents of the Inguinal Canal

• In Males:

  • Spermatic cord

  • Ductus deferens

  • Testicular artery

  • Cremasteric artery

  • Pampiniform plexus

  • Sympathetic nerve fibers

  • Genital branch of genitofemoral nerve

  • Lymphatic vessels

• In Females:

  • Round ligament of the uterus

Hernias

• Direct Inguinal Hernia:

  • Acquired

  • Protrudes through superficial ring only

  • Medial to inferior epigastric vessels

  • Does not typically enter the scrotum

• Indirect Inguinal Hernia:

  • Congenital

  • Protrudes through both superficial and deep rings

  • Lateral to the inferior epigastric vessels

  • Often associated with a patent processus vaginalis

Learning Objectives

1. Describe the layers and musculature of the abdominal cavity.

2. Explain the formation of the rectus sheath and its changes at the umbilicus.

3. Understand the nerve supply of the anterior abdominal wall.

4. Describe the vasculature of the anterior abdominal wall.

5. Discuss the anatomy of the bony pelvis related to the inguinal ligament.

6. Understand the anatomy of the inguinal canal, including boundaries and contents.

7. Differentiate between direct and indirect inguinal hernias.