Normal Inguinal Anatomy

Figure 16-2 depicts normal anatomy of the inguinal region. The surgically relevant structures will be reviewed in the following order: (1) fascial structures, (2) vasculature, (3) spermatic cord structures, and (4) nerves.

The inguinal ligament is formed from the aponeurosis of the external oblique muscle, and extends from the anterior superior iliac spine to the

Rectus sheath

Cross section above arcuate line

Rectus sheath

Cross section above arcuate line

Aponeurosis of internal oblique muscle splits to form anterior and posterior layers of rectus sheath. Aponeurosis of external oblique muscle joins anterior layer of sheath; aponeurosis of transversus abdominis muscle joins posterior layer. Anterior and posterior layers of rectus sheath unite medially to form linea alba

Aponeurosis of internal oblique muscle splits to form anterior and posterior layers of rectus sheath. Aponeurosis of external oblique muscle joins anterior layer of sheath; aponeurosis of transversus abdominis muscle joins posterior layer. Anterior and posterior layers of rectus sheath unite medially to form linea alba

Figure 16-1 (Continued)

pubic tubercle. Posteromedially, the inguinal ligament forms the lacunar ligament, which extends from the pubic tubercle to the iliopectineal line. Further posteriorly, the lacunar ligament connects with the iliopectineal ligament, which runs along mediolaterally along the superior pubic ramus.

The inguinal ligament and the iliopectineal ligament form two sides of a triangle, with the lacunar ligament at one vertex. The third side of the triangle is formed by the iliopsoas muscle. The external iliac artery (lateral) and vein (medial) lie on the anterior surface of the iliopsoas, and course through this fascial triangle (termed the femoral sheath), deep to the inguinal ligament. Once the vessels pass posterior to the inguinal ligament, they are renamed the common femoral artery and vein, respectively. Medial to the external iliac/ common femoral vein is the femoral canal. Femoral hernias occur through this space. Finally, the inferior epigastric vessels are the last branches of the external iliac vessels, prior to their passage under the inguinal ligament.

The spermatic cord in the male and round ligament in the female pass from posterior to anterior through the deep inguinal ring laterally, and then through the superficial inguinal ring medially. The deep inguinal ring is a foramen in the transversalis fascia lateral to the inferior epigastric vessels, while the superficial ring is a foramen in the external oblique fascia. Finally, the nerves of concern in inguinal hernia are the genitofemoral and ilioinguinal.

Rectus sheath (posterior layer)

Deep inguinal ring

Rectus abdominis muscle

Linea alba

Inguinal

(Hesselbach's)

triangle

Inguinal falx

(conjoint tendon)

Rectus sheath (posterior layer)

Deep inguinal ring

Rectus abdominis muscle

Linea alba

Inguinal

(Hesselbach's)

triangle

Inguinal falx

(conjoint tendon)

Transversalis fascia (cut away)

Pubic symphysis

Obturator artery

Superior pubic ramus

Lacunar ligament (Gimbernat)

Transversalis fascia (cut away)

Anterior superior iliac spine

Iliopubic tract

Testicular vessels and genital branch of genitofemoral nerve

Iliopsoas fascia (covering femoral nerve)

Iliopsoas muscle

External iliac vessels

-Femoral ring (dilated) (circle)

Obturator-pubic arterial anastomosis

Ductus (vas) deferens Pectineal ligament (Cooper)

Pubic symphysis

Obturator artery

Superior pubic ramus

Lacunar ligament (Gimbernat)

Figure 16-2 Normal inguinal anatomy. The right inguinal region is viewed from posterior to anterior. (Source: The Netter Collection. Icon Learning Systems.)

The genitofemoral nerve is derived from roots L1-2, and runs on the anterior surface of the iliopsoas muscle, and divides into genital and femoral branches. The genital branch passes through the deep inguinal ring, and supplies the cremaster muscle. The femoral branch passes through the femoral sheath and supplies skin overlying the femoral triangle. The ilioinguinal nerve is derived from roots T12-L1, and is formed with the iliohypogastric nerve. It runs along the iliacus muscle, and then passes the anterior iliac crest en route to lying between the internal and external oblique muscles. The nerve then passes through the superficial inguinal ring, and supplies the superomedial thigh and superior portion of the scrotum.

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