Lecture Notes - Abdominal Wall

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Boundaries of the Abdomen:
• Superior Boundary: The diaphragm: Fifth intercostal space.
• Posterior Boundary: Lumbar Vertebrae and Quadratus Lumborum mm.
• Anterolateral Borders: The muscles of abdominal wall.
• Inferior Borders: The 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 oblique: the aponeurosis forms the inguinal ligament and the superficial inguinal ring. Superficial Inguinal Ring 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 separate the two.
        
     2. internal oblique
        
     3. transversus abdomins
   • 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).

Inguinal lymph nodes: horizontal and vertical groups
Vessels: (anastamosis)
• Superficial epigastric art.
• Superficial external pudendal art.
• Superficial circumflex iliac art.
Deeper vessels:
• Superior and inferior epigastric (inside rectus sheath)
• Intercostal
• Deep circumflex iliac
Rectus sheath: Arcuate Line: The line that 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. oblique	ext.; int.; & transversus abdominis
Posterior	Int. oblique & transversus abdominis	none; only transversalis fascia ("not suturable" in surgery)


Linea Alba: fused midline layers of the sheath between the 2 recti. The best place to make a surgical cut and not hit any nerves.