Fascia

Transversalis Fascia

The transversalis fascia is a component of an extensive thin layer of fascia that lies between the muscle layer of the abdominal wall and the parietal peritoneum (Fig. 6.21; also see Fig. 6.17). It is continuous below with a similar fascial layer lining the pelvic walls. Customarily, this fascia is named according to the structure it overlies. For example, the diaphragmatic fascia covers the undersurface of the diaphragm, the transversalis fascia lines the transversus abdominis, the psoas fascia covers the psoas muscle, the quadratus lumborum fascia covers the quadratus lumborum, and the iliac fascia covers the iliacus muscle.

The abdominal blood and lymph vessels lie within this fascial lining, whereas the principal nerves lie outside the fascia. This fact is important in understanding the femoral sheath (see Fig. 6.21). This sheath is simply a downward prolongation of the transversalis and iliac fascial linings around the femoral vessels and lymphatics, for about 1.5 in. (4 cm) into the thigh, behind the inguinal ligament. Because the femoral nerve lies outside the fascial envelope, it has no sheath (also see Chapter 11).

In certain areas of the abdominal wall, the fascial lining performs particularly important functions. Inferior to the level of the arcuate line, the posterior wall of the rectus sheath is devoid of muscular aponeuroses and is formed by the transversalis fascia and parietal peritoneum only (see Figs. 6.17 and 6.18).

At the midpoint between the anterior superior iliac spine and the symphysis pubis, the spermatic cord pierces the transversalis fascia to form the deep inguinal ring (see Fig. 6.15). From the margins of the ring, the fascia continues over the cord as a tubular sheath, the internal spermatic fascia (see Fig. 6.11).

Extraperitoneal Fascia

The extraperitoneal fascia is a thin layer of connective tissue that contains a variable amount of fat. It lies between the transversalis fascia and the parietal peritoneum (see Fig. 6.17B).

Parietal Peritoneum

The deep sides of the walls of the abdomen are lined with parietal peritoneum (see Figs. 6.17B and 6.21). This is a thin serous membrane and is continuous below with the parietal peritoneum lining the pelvis (see Chapters 7 and 9).

Nerve Supply

The phrenic nerves supply the central part of the diaphragmatic parietal peritoneum, and the lower intercostal nerves supply the peripheral part. The segmental intercostal and lumbar nerves, which also supply the overlying muscles and skin, supply the peritoneum lining the anterior and posterior abdominal walls.