11 Hernias
Anatomy of the Abdominal Wall
Abdominal Wall Layers
• Following are layers from the surface in.
Superficial fascia with a variable amount of subdermal fat: Camper’s fascia, overlying membranous Scarpa’s fascia (subumbilical level)
Muscle bellies and aponeuroses of the rectus abdominis, external and internal obliques, and transversus abdominis muscles
Superficial fascia with a variable amount of subdermal fat: Camper’s fascia, overlying membranous Scarpa’s fascia (subumbilical level) Muscle bellies and aponeuroses of the rectus abdominis, external and internal obliques, and transversus abdominis muscles
External Oblique (EO) Muscle
• On each side, the lower border of its aponeurosis attaches to anterior superior iliac spine and pubic tubercle to form the inguinal ligament.
• Distally, a portion of EO aponeurosis fibers arch posteriorly to insert on the superior pubic ramus, forming the lacunar ligament (of Gimbernat).
• Most lateral of these deep (lacunar) fibers continue to run along the pectin of pubis as the pectineal ligament (of Cooper).
• Some of the most distal fibers arch upward, avoid the pubic tubercle, and merge with the opposite side’s fibers as the reflected inguinal ligament.
• Most muscle and aponeurotic fibers run superolateral to inferomedial (“hands in pockets” orientation).
• Superficial (external) inguinal ring: division in the most inferior aponeurosis; spermatic cord or round ligament passes through
Internal Oblique (IO) Muscle
• Fibers run deep, approximately perpendicular to the external oblique layer, from the deep lumbar aponeurosis, curving anteriorly then medially.
• Medial IO aponeurosis layer splits to pass around the rectus, as the middle layer of the rectus sheath, above the semicircular lines (of Douglas).
• On each side, the inferior triangle of the IO aponeurosis fuses with the transversus aponeurosis to form the conjoined (conjoint) tendon.
Transversus Abdominis (TA) Muscle
• Fibers run deep to the internal oblique layer, mostly posteriorly, becoming largely aponeurotic laterally in the deep back.
• Medial aponeurotic fibers pass posterior to the rectus, as the posterior layer of the rectus sheath, above the semicircular lines (of Douglas).
• On each side, the inferior triangle of the TA aponeurosis fuses with the internal oblique aponeurosis to form the conjoined (conjoint) tendon.
• Deep (internal) inguinal ring: gap in the transversus abdominis, lateral to the inferior epigastric arteries
Rectus Abdominis Muscle
• Parallel segments of muscle with vertically running fibers; segments joined end-to-end by tendinous insertions (inscriptions)
• External oblique aponeurosis is always the most superficial (anterior) component of the rectus sheath.
• Internal oblique aponeurosis splits to run in front of and behind rectus in the sheath above the semilunar lines (somewhat above umbilicus).
• External and internal oblique and transversus aponeuroses components of rectus sheath pass anterior to the rectus below the semicircular lines (below the umbilicus).
Linea Alba
• Midline, tendinous junction between right and left portions of the rectus sheath and the underlying midline tendons of the rectus muscle segments
Transversalis Fascia
• Tough fascial layer just deep to the transversus muscle and aponeurosis, rectus sheath, and rectus abdominis anteriorly
• Male transversalis fascia outpockets through the deep (internal) inguinal ring, a gap in the transversus abdominis, lateral to the inferior epigastric arteries.
• Internal spermatic fascia: transversalis fascia layer surrounding the layers of the tunica vaginalis around the descended testis, its duct, and vessels
• Iliopubic tract: thickened inferior margin of the transversalis fascia, running parallel, posterior, and deep to the inguinal ligament (reinforcing)
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