1 Surgeons have traditionally been taught the anatomy of the abdominal wall from an outside to inside

perspective. However, with the increasing use of intra-abdominal or preperitoneal approaches to

abdominal wall reconstruction, a better understanding of the anatomy from the inside to the outside

perspective is important. The anatomy of the abdominal wall and the inguinal region are presented,

first from the viewpoint of the surgeon using open techniques and subsequently from the perspective

of the surgeon utilizing the laparoscope. Anatomic terms for which synonyms and eponyms are

commonly used are listed in Table 72-1. Specific anatomic nomenclature can now be found in

Terminologia Anatomica, the successor to Nomina Anatomica.

The abdominal wall spans the gap between the lower ribs and the pelvis; the lowest ribs, pelvic brim,

and lumbar spine comprise its only skeletal support. The muscular and aponeurotic structures that

provide much of the integrity of the wall must not only compress and contain abdominal viscera but

also contribute to the support and movement of the spine and pelvis.

The sheets of relatively thin muscles and aponeuroses that make up the abdominal wall would,

individually, seem to predispose to visceral eventration. However, the laminar layout of these sheets

over most of the wall precludes this in most cases. The most common sites of hernia formation are

found between laminations, where only peritoneum and fascia are found between the viscera and skin.

These weak areas are most important to the hernia surgeon and are described in detail in the subsequent

sections dealing with the anterior and posterolateral abdominal wall and the inguinal region.

Anterior Abdominal Wall

Superficial Fascia, Vessels, and Nerves

The anterior abdominal wall does not consist solely of muscle and aponeurosis; it can also be the

repository for copious amounts of adipose tissue (panniculus adiposus) in its superficial fascial layer,

often called Camper fascia. This layer, which is continuous inferiorly with the outer layer of fascia

covering the perineum and genitalia, also contains the dartos muscle fibers of the scrotum. The major

blood vessels of the superficial fatty layer are the superficial epigastric vessels and superficial

circumflex iliac vessels, which are tributaries of the femoral vessels. The superficial fascia is also replete

with lymphatic vessels that drain into the inguinal lymph nodes inferior to the umbilicus. The lymphatic

structures cross the inguinal ligament, so that they are potentially placed in the surgical field during

open herniorrhaphy.

Table 72-1 Anatomic Terms with Common Synonyms and Eponyms

A second fascial layer in the superficial abdominal wall is the deep fascia of Scarpa. Although most

commonly considered a distinct anatomic layer, Scarpa fascia actually consists of compressed fibrous

components of the superficial fascia.3 The deeper fibrous tissue of the superficial fascia forms the

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fundiform ligament of the penis (suspensory ligament of the female clitoris), continues onto the penis

and scrotum, and ultimately fuses with the superficial fascia of the perineum.

Figure 72-1. The myopectineal orifice. Superior to the inguinal ligament, this area includes the inguinal (Hesselbach) triangle.

Inferior to the ligament, the orifice transmits the iliopsoas muscle, the femoral nerve and vessels, and the femoral canal and sheath.

(Reproduced with permission from Wantz GE. Atlas of Hernia Surgery. New York, NY: Raven Press; 1991:4.)

The superficial fascia also fuses with the layer of fascia (fascia innominata) investing the external

abdominal oblique muscle. This fascia is bound inferiorly to the inguinal ligament and pubis before

continuing onto the thigh, where it blends with the fascia lata to seal the space beneath and inferior to

the inguinal ligament, which is the inferior portion of the myopectineal orifice (Fig. 72-1). This portion

of the inguinal region includes the Hesselbach (inguinal) triangle superiorly and therefore constitutes

the weakest aspect of the groin.

The skin of the anterior abdominal wall is segmentally innervated in the familiar dermatome pattern.

The nerve branches to this area are derived from the anterior and lateral cutaneous branches of the

ventral rami of the 7th to 12th intercostal nerves and from the ventral rami of the first and second

lumbar nerves. Disruption of one of these nerves is rarely noted by the postoperative patient because

the dermatome fields overlap significantly. The anterior and lateral cutaneous branches reach the

subcutaneous layer by coursing between the flat lateral muscles and by piercing the sheath of the rectus

abdominis.

Anterior Musculature and Ligaments

The division of the wall into anterior and posterior segments is somewhat artificial because the anterior

muscles, with the exception of the rectus abdominis, arise posteriorly and also form part of the posterior

wall.

The three muscles of the lateral aspect of the anterior abdominal wall (Fig. 72-2) are composed of a

variable amount of muscle with a large aponeurosis. The aponeurosis is the tendon of insertion for the

lateral muscles, and it also forms the sheath of the rectus abdominis. The midline decussation of the

three aponeuroses forms the linea alba. Fibrous tissue layers are of great importance to the hernia

surgeon because of their ability to support sutures. Fascia and aponeurosis are terms commonly used to

describe these fibrous structures, but are often confused and used interchangeably. In this chapter, an

aponeurosis is defined as the non–muscle-fiber-containing portion of a muscle usually present at

insertion points. Muscle fibers are said to “give way” to the corresponding aponeurosis. Fascia, on the

other hand, is the fibrous tissue that lines or envelops muscles.

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Figure 72-2. Pattern of crossing of the aponeurotic fascicles of the abdominal wall musculature. A: Fascicles from the right

external oblique and anterior lamina of the left internal oblique. B: Fascicles from the right transversus abdominis and posterior

lamina of the left internal oblique. C: Fascicles between the right and left transversus abdominis muscles.

External Abdominal Oblique Muscle and Associated Ligaments

The external abdominal oblique muscle (Figs. 72-2 and 72-3A,B) is the most superficial of the three

lateral abdominal muscles. The external abdominal oblique arises from the posterior aspects of the

lower eight ribs and interdigitates with both the serratus anterior and the latissimus dorsi at its origin.

The direction of the muscle fibers varies from nearly horizontal in its upper portion to oblique in the

middle and lower portions. The mostly horizontal fibers, which originate posteriorly, insert onto the

anterior portion of the iliac crest. The obliquely arranged anteroinferior fibers of insertion fold on

themselves to form the inguinal ligament. The remaining portion of the aponeurosis inserts into the

linea alba after contributing to the anterior portion of the rectus abdominis sheath. Some fibers cross

the linea alba to reinforce further the anterior rectus sheath of the opposite side.

The more medial fibers of the aponeurosis of the external oblique divide into a medial and a lateral

crus to form the external or superficial inguinal ring. The spermatic cord (or round ligament) and

branches of the ilioinguinal and genitofemoral nerves pass through this opening. The inguinal ligament

(Fig. 72-4) is worthy of special consideration because of its important role as both a landmark and an

integral component of many groin hernia repairs. The inguinal ligament is formed by obliquely oriented

anteroinferior aponeurotic fibers of the external abdominal oblique. The ligament is formed when the

aponeurosis folds beneath itself. Its lateral attachment is to the anterior superior iliac crest; its medial

insertion is primarily on the pubic tubercle.

The medial insertion of the inguinal ligament in most persons is dual. One portion runs along the

superior surface of the pubic tubercle and symphysis to form (or at least reinforce) the superior pubic

ligament. The other portion is fan shaped and spans the distance between the inguinal ligament proper

and the pectineal line of the pubis. This fan-shaped portion of the ligament is called the lacunar ligament

(Fig. 72-4). It blends laterally with the pectineal (Cooper) ligament.

Internal Abdominal Oblique Muscle and Aponeurosis

The middle layer of the lateral abdominal group is the internal abdominal oblique muscle (Figs. 72-2

and 72-3B,C). This muscle primarily arises from the iliac fascia along the iliac crest and forms a band of

iliac fascia fused with the inguinal ligament. The uppermost fibers course obliquely toward the distal

ends of the lower three or four (“floating”) ribs. The muscle fibers of the internal oblique fan out

following the shape of the iliac crest so that the lowermost fibers are directed inferiorly. These fibers

arch over the round ligament, or spermatic cord. Some of the lower muscle bundles in the male join

fibers of the transversus abdominis to form the cremaster muscle. The aponeurosis of the internal

oblique (Fig. 72-5A) above the level of the umbilicus splits to envelop the rectus abdominis, re-forming

in the midline to join and interweave with the fibers of the linea alba. Below the level of the umbilicus

(Fig. 72-5B), the aponeurosis does not split but rather runs anterior to the rectus muscle, continues

medially as a single sheet, joins the anterior rectus sheath, and finally contributes to the linea alba. The

aponeurotic portion of the internal oblique is widest at the level of the umbilicus.

Transversus Abdominis Muscle and Aponeurosis

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