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• The abdominal musculaturehas three distinct layers that take three dif-
  ferent directions. The external oblique muscle, internal oblique muscle,
  and transverse abdominis muscle may be sequentially split and retracted
  so that extensive suturing is unnecessary to provide a strong repair
  (McBurney’s incision).


• Because the linea albais relatively avascular, incisions may not heal well
  and predispose to epigastric herniation.


• Above the arcuate line,the anterior leaf of the rectus sheathis formed
  by fusion of the external oblique and internal oblique aponeuroses; the
  posterior leaf is formed by fusion of the internal oblique and transverse
  abdominis aponeuroses.


• Below the arcuate line,the anterior leaf of the rectus sheath is formed
  by fusion of all three aponeuroses and there is no posterior leaf.


• The inferior epigastric arterypasses into the rectus sheath at the arcuate
  line. This is a potential site for spigelian herniation into the rectus sheath.

High-Yield Facts 53

ABDOMEN

Abdominal Wall

T4 Nipple

T7 Xiphoid process

T10 Umbilicus

L1 Inguinal ligament

DERMATOMAL LANDMARKS

Dermatome Region

Direct inguinal Through the inguinal triangle bounded by inguinal ligament,

inferior epigastric artery, and rectus abdominis—therefore, medial

to the inferior epigastric artery. Exits through the superficial

inguinal ring generally adjacent to the spermatic cord. Usually

acquired

Indirect inguinal Through the deep inguinal ring and along the inguinal canal—

therefore, lateral to the inferior epigastric artery. Exits through the

superficial ring within the spermatic cord. Usually congenital

Femoral Passes inferior to the inguinal ligament through the femoral ring

into the thigh. More prevalent in women

HERNIA CHARACTERISTICS

Hernia Pathway