213Anatomy

LAYERS OF THE ABDOMEN

Layers of the abdomen (from superficial to deep): skin, Camper’s fascia, Scarpa’s fascia, deep fascia (composed of the aponeuroses of the external oblique, internal oblique, and transversus muscles). The transversalis fascia lies below the transversus muscle. Superior to the arcuate line, the internal oblique aponeurosis splits to envelop the rectus abdominis muscle. Inferior to the arcuate line, the internal oblique and transversus abdominis aponeuroses merge and pass superficial (i.e., anteriorly) to the rectus muscle (Figure 4.1).

LIGAMENTS

•   Infundibulopelvic: contains ovarian vessels and nerves

•   Round: originates from the uterine cornua, passes through the inguinal ring, the inguinal canal, and inserts into the labia majora. The male counterpart to this ligament is the gubernaculum testis. A small evagination of peritoneum (canal of Nuck) accompanies the round ligament through the inguinal ring.

•   Utero-ovarian: these contain the utero-ovarian vessels between the ovary and the uterus. They represent the proximal portion of the gubernaculum testis.

•   Cardinal (Mackenrodt’s ligaments): located laterally to the cervix, they originate from thickening of the endopelvic fascia. They are the main support for pelvic organs.

•   Uterosacral: located posterior to the cervix, they originate from thickening of the endopelvic fascia. They insert on the anterior surface of S2 to S4.

VASCULATURE

•   Ovarian vessels: travel through the infundibulopelvic ligaments. The ovarian arteries arise from the abdominal aorta, below the renal arteries. The left ovarian vein drains to the left renal vein. The right ovarian vein drains to the inferior vena cava (Figure 4.2).

•   Artery of Sampson: travels through the round ligament

•   External iliac artery and vein: become the femoral vessels after they pass under the inguinal ligament. There are two branches of the external iliac artery and vein: the deep circumflex iliac and the inferior epigastric.

•   The internal iliac artery and vein are also known as the hypogastric. Branches of the internal iliac artery:

        Posterior division: iliolumbar, lateral sacral (superior and inferior), superior gluteal

        Anterior division: inferior gluteal, internal pudendal, obturator, middle rectal, uterine, vaginal, inferior vesical, superior vesical, obliterated umbilical

•   Branches of the celiac trunk: left gastric, common hepatic (branches: right gastric, gastroduodenal), splenic

•   Omental blood supply: right and left gastroepiploics, from the gastro-duodenal and splenic vessels, respectively

•   Short gastric arteries originate from the splenic artery

•   Marginal artery of Drummond: collateral blood supply for the large bowel

•   Blood supply to bowel is from two main arteries, the superior and inferior mesenteric arteries.

        Superior mesenteric artery (SMA) supplies the:

             Small bowel is supplied by the SMA

             Right colon is supplied by right colic and ileocolic arteries which are branches of the SMA

             Appendix: ileocolic branch of the SMA

             Transverse colon: middle colic branch of the SMA

        Inferior mesenteric artery (IMA) supplies the:

             Descending colon: left colic branch of the IMA

             Sigmoid colon and rectum: sigmoid arteries, superior hemorrhoidal artery branches of the IMA

NERVES

The following nerves are composed of contributing spinal nerve roots:

•   Brachial plexus: C5, C6, C7, C8, and T1

        Injury can cause paresthesias of the radial, ulnar, or median nerves.

        Etiology of injury is from traction on the extended arm or neck.

•   Genitofemoral nerve: L1 and L2

        It arises on the medial border of the psoas muscle. It is a sensory nerve to the medial thigh, and motor innervation to the cremaster muscle.

        Injury can cause paresthesia or anesthesia of the labia or skin of the superior thigh.

        Etiology of injury is transection or traction of the nerve along the psoas muscle.

•   Ilioinguinal nerve: L1

        It arises on the anterior abdominal wall between the internal oblique and transversus abdominis muscles. It supplies the skin over the pubic symphysis.

        Injury can cause paresthesia or anesthesia of the lower abdomen. Etiology of injury is commonly from scar fibrosis.

•   216Lateral femoral cutaneous nerve: L2 and L3

        Injury can cause paresthesia or anesthesia to the anterior and lateral thigh.

•   Femoral nerve: L2, L3, L4

        Injury can cause paresthesia or anesthesia to the anterior and medial thigh, groin pain, weakness of knee extension, and thigh flexion.

        Etiology of injury is often from retractor placement, stirrup positioning, and tumor invasion.

•   Obturator nerve: L2, L3, L4

        It emerges from the medial border of the psoas muscle, traverses the obturator space.

        Injury can cause sensory loss to the upper and medial thigh, and weakness in hip adductors.

        Etiology of injury is commonly transection during lymph node (LN) dissection.

•   Accessory obturator nerve: L3 and L4

        It is present in 5% to 30% of patients.

•   Internal pudendal nerve: S1, S2, and S3

        Injury can cause sensory loss to the labia.

•   Sciatic nerve: L5 and S1

        Injury can cause paresthesias of the posterior leg skin and hamstring areas and difficulty with knee flexion.

        Etiology of injury is from stretch injury from poor stirrup positioning.

•   Common peroneal nerve: L4, L5, S1, S2

        Symptoms are foot drop.

        Etiology of injury is usually from poor stirrup positioning.

•   Autonomic nerves

        Symptoms are large bowel dysfunction and urinary retention.

        Etiology of injury is from radical pelvic surgery or tumor invasion of the autonomic plexus.

VULVAR AND GROIN ANATOMY

•   The anatomical boundaries of the groin form the femoral triangle. This is bounded superiorly by the inguinal ligament, the sartorius muscle laterally to medially, and the adductor longus muscle medially to laterally. The base of the triangle consists of the iliacus, iliopsoas, and pectineus muscles, laterally to medially.

•   Through the triangle run the femoral nerve and three other smaller nerves. The femoral nerve consists of the anterior femoral cutaneous branch and the medial femoral cutaneous branches from the L1, L2, and L3 nerve roots. The lateral femoral cutaneous nerve runs on top of the iliopsoas muscle and originates from L1. The genital–femoral nerve runs medial to the psoas muscle in the abdomen and originates from the L1 and L2 nerve roots. The ilioinguinal nerve also runs through the triangle and originates in the L1 root.

•   Innervation to the vulva is from branches of the genitofemoral nerve and the perineal branch of the posterior femoral cutaneous nerve (a branch of the femoral nerve). The internal pudendal nerve also provides innervation to the vulva.

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