Lecture Notes - Abdominal Wall and Inguinal Region

Boundaries of the Abdomen:

• Superior boundary: diaphragm (rises to level of 5th intercostal space)
• Posterior boundary: lumbar vertebrae and quadratus lumborum mm.
• Anterolateral borders: muscles of abdominal wall
• Inferior borders: pelvic brim
  

Anterior Superior Iliac Spine (ASIS): The anterior most feature on the iliac crest
Pubic Tubercle: Lateral edge of pubic bone
Inguinal Ligament: Extends between the ASIS and the pubic tubercle
Umbilicus: Usually between L3 and L4 in physically fit persons.

Clinical relevance:

• Quadrants (4): upper and lower right and left
• Incisions and hernias

Layers of Anterior abdominal Wall:

1. Skin
2. Superficial fascia: fatty (Camper's) and membranous (Scarpa's)
3. Deep fascia
4. Muscles
   • Lateral (flank):
     1. External abdominal oblique: its aponeurosis forms the inguinal ligament and the superficial inguinal ring, which allows passage of the spermatic cord (male) or round ligament (female) and is made up of two components, lateral crus and medial crus. Intercrural fibers unite the two.
        
     2. Internal abdominal oblique
        
     3. Transversus abdominis
   • Anterior: rectus abdominis
5. Fascia: thoracolumbar; rectus sheath; transversalis fascia
6. Extraperitoneal connective tissue (preperitoneal fat)
7. Peritoneum: parietal

Innervation: intercostal (T7-T12); iliohypogastric and ilioinguinal (L1)

Superficial inguinal lymph nodes: horizontal and vertical groups

Superficial vessels:

• Superficial epigastric a. and v.
• Superficial external pudendal a. and v.
• Superficial circumflex iliac a. and v.

Deeper vessels:

• Superior and inferior epigastric (inside rectus sheath) a. and v.
• Posterior intercostal a. and v.
• Deep circumflex iliac a. and v.

Rectus sheath:

• Arcuate Line: divides the upper 3/4 of abdomen wall from lower 1/4, by the differences in the aponeurotic layers.
  
  

• Layers:	Above arcuate line ("suturable" in surgery)	Below arcuate line
  Anterior	ext. & int. abdominal oblique	ext. and int. abdominal oblique & transversus abdominis
  Posterior	Int. abdominal oblique & transversus abdominis	none; only transversalis fascia ("not suturable" in surgery)

Linea Alba: fused midline layers of the aponeuroses between the 2 recti. The best place to make a surgical cut and not hit any nerves. Descent of Gonads (Ovary & Testis): develop and migrate retroperitoneally

Gubernaculum: a ligamentous structure that runs between the lower pole of each gonad to each labial/scrotal fold. In the female it becomes the round ligament

Ovary: reaches and remains in the pelvis by the 3rd month.
Definitive ovary: reaches deep pelvis trailing its vessels & nerves.

Testis:

• Processus vaginalis (peritoneal pouch; evaginates into developing scrotum, lies ahead of testis during descent)
• Reaches deep inguinal ring by 7th month
• Passes through inguinal canal between 7-8 months
• Reaches scrotum before birth
• Around birth: processus vaginalis closes off from peritoneum and forms tunica vaginalis testis

Patent processus vaginalis predisposes to congenital inguinal hernia

Coverings of the Spermatic Cord:

1. external spermatic fascia: derived from ext. abdominal oblique fascia
2. cremaster muscle and fascia: derived from int. abdominal oblique muscle and fascia
3. Internal spermatic fascia: derived from transversalis fascia

Components of the spermatic cord:

1. ductus deferens
2. testicular artery
3. pampiniform plexus of veins
4. nerves (autonomic) and lymphatics
5. genital branch of genitofemoral nerve

Inguinal Canal: a diagonal passage formed by the aponeuroses of the three flat abdominal muscles

Contents of Inguinal Canal

• Spermatic Cord (male) or Round Ligament (female)
• Ilioinguinal Nerve

Boundaries:

1. Superficial inguinal ring: triangular defect in the ext. abdominal oblique aponeurosis
2. Deep inguinal ring: in the transversalis fascia
3. Anterior wall: int. abdominal oblique muscle (laterally) and external abdominal oblique aponeurosis (medially)
4. Roof: falx inguinalis (arching inferior fibers of internal abdominal oblique muscle)
5. Floor: inguinal ligament and lacunar ligament (medially)
6. Posterior wall: transversalis fascia (weak fascia) laterally and conjoint tendon (medially)

Boundaries of Inguinal Triangle (of Hesselbach):

1. Medially: lateral edge of rectus abdominis (linea semilunaris)
2. Laterally: inferior epigastric artery
3. Inferiorly: inguinal ligament

Abdominal Wall Hernias:

1. Inguinal: hernia passes through the inguinal canal for a variable distance and exits through the superficial inguinal ring
   • Indirect:
     • Congenital: through patent processus vaginalis
     • Acquired: passes through deep inguinal ring initially, i.e lateral to the inferior epigastric artery and exits through the superficial ring
   • Direct: passes medial to the inferior epigastric artery (in the inguinal triangle) and may pass through the superficial inguinal ring
2. Femoral: below inguinal ligament
3. Obturator
4. Other: umbilical; lumbar; incisional; hiatal; etc.