Beneath the subcutaneous layer, the anterior abdominal wall muscles consist of the midline rectus abdominis and pyramidalis muscles as well as the external oblique, internal oblique, and transversus abdominis muscles, which extend across the entire wall (Fig.
The ibrous aponeuroses of these three latter muscles form the primary fascia of the anterior abdominal wall. These fuse in the midline at the linea alba, which normally measures 10 to 15 mm wide below the umbilicus (Beer, 2009). n abnormally wide separation may reflect diastasis recti or hernia.
These three aponeuroses also invest the rectus abdominis muscle as the rectus sheath. The construction of this sheath varies above and below a boundary, termed the arcuate line (see Fig. 2-1). Cephalad to this border, the aponeuroses invest the rectus abdominis bellies on both dorsal and ventral surfaces. Caudal to this line, all aponeuroses lie ventral or supericial to the rectus abdominis muscle, and only the thin transversalis fascia and peritoneum lie beneath the rectus (Loukas, 2008). This transition of rectus sheath composition can be seen best in the upper third of a midline vertical abdominal incision.
he paired small triangular pyramidalis muscles originate from the pubic crest and insert into the linea alba. These muscles lie atop the rectus abdominis muscle but beneath the anterior rectus sheath.
he supericial epigastric, supericial circumlex iliac, and supericial external pudendal arteries arise from the femoral artery just below the inguinal ligament within the femoral triangle
Rectus abdominis m.
External oblique m.
Internal oblique m.
Transversus abdominis m.
Lateral cutaneous n.
Genital branch of genitofemoral n.
Internal thoracic a.
Superior epigastric a.
Inferior epigastric a.
Superficial circumflex iliac a.
External pudendal a.
with emerging round ligament, ilioinguinal & genitofemoral nn.
FIGURE 2-1 Anterior abdominal wall anatomy. (Modified with permission from Corton MM: Anatomy. In Hoffman BL, Schorge JO, Bradshaw KD, et al (eds): Williams Gynecology, 3rd ed. New York, McGraw-Hili Education, 2016) (see Fig. 2-0. These vessels supply the skin and subcutaneous layers of the anterior abdominal wall and mons pubis. Of these three, the superficial epigastric vessels are surgically important to the obstetrician and course diagonally from their origin toward the umbilicus. With a low transverse skin incision, these vessels can usually be identified at a depth halway between the skin and the anterior rectus sheath. They lie above Scarpa fascia and several centimeters from the midline. Ideally, these vessels are identiied and surgically occluded.
In contrast, the inferior "deep" epigastric vessels are branches of the external iliac vessels and supply anterior abdominal wall muscles and fascia. Of surgical relevance, the inferior epigastric vessels initially course lateral to, then posterior to the rectus abdominis muscles, which they supply. Above the arcuate line, these vessels course ventral to the posterior rectus sheath and lie between this sheath and the posterior surface of the rectus muscles. Near the umbilicus, the inferior epigastric vessels anastomose with the superior epigastric artery and vein, which are branches of the internal thoracic vessels. Clinically, when a Maylard incision is used for cesarean delivery, the inferior epigastric vessels may be lacerated lateral to the rectus belly during muscle transection. Preventively, identiication and surgical occlusion are preferable. These vessels rarely may rupture following abdominal trauma and create a rectus sheath hematoma (Toicher, 2010; Wai, 2015).