A thorough understanding of pelvic, perineal, and anterior abdominal wall anatomy is essential for obstetric practice and surgery. Although anatomic consistencies can be expected, marked variation may be encountered among women and in individual women as pregnancy advances. This is especially true for major blood vessels and genitourinary structures.
The anterior abdominal wall plays several roles during pregnancy. It confines the abdominopelvic viscera; contributes muscular action for respiration, elimination, and parturition; and stretches to accommodate the expanding uterus. For cesarean delivery, the anterior abdominal wall must be divided to gain surgical access to the internal reproductive organs. Thus, a comprehensive knowledge of its layered structure is required for safe and effective entry into the peritoneal cavity. The layers of the anterior abdominal wall include the skin and subcutaneous layer, which receive blood supply from the femoral artery, and the muscles and fascia, which are supplied by branches of the external iliac artery (Fig. 3-1).
Anterior abdominal wall anatomy. (Reproduced with permission from Corton MM: Anatomy. In Hoffman BL, Schorge JO, Bradshaw KD, et al (eds): Williams Gynecology, 3rd ed. New York, McGraw-Hill Education, 2016.)
Skin and Subcutaneous Layer
Langer lines correspond to the natural orientation of collagen fibers within the skin and are generally parallel to the orientation of the underlying muscle fibers. In the anterior abdominal wall, they are mostly arranged transversely. As a result, vertical skin incisions sustain greater lateral tension compared with low transverse incisions such as the Pfannenstiel, and thus generally develop wider scars.
The subcutaneous layer can be separated into a superficial, predominantly fatty layer known as Camper fascia, and a deeper, more fibrofatty layer known as Scarpa fascia. Camper fascia continues onto the perineum to provide fatty substance to the mons pubis and labia majora. Scarpa fascia continues inferiorly onto the perineum as Colles fascia, which is also known as the superficial perineal fascia (p. 31). Thus, blood or infection within the subcutaneous layer of the anterior abdominal wall can extend to the perineum, and vice versa.
Clinically, Scarpa fascia is better developed in the lower abdomen, and during surgery it can be best identified in the lateral portions of a low transverse incision. In contrast, this fascia is rarely recognized during midline vertical incisions and may be absent at the umbilicus (Martin, 1984).
The anterior abdominal wall muscles consist of the midline rectus abdominis and pyramidalis muscles as well as the more lateral external and internal oblique and transversus abdominis muscles. These last three muscles, often called the flank muscles, contain a lateral muscular portion and a medial fibrous aponeurotic portion. The aponeuroses of these muscles contribute to the primary fascia ...