16th February 2024

Abdominal wall and peritoneum

Abdominal wall

The abdominal wall can be divided into the anterior, posterior, and inguinal canals. 

Anterior abdominal wall

The abdominal wall is made up of 4 muscles: external and internal obliques, transverses abdominis and rectus abdominis. The aponeurosis of the former three muscles comes together to form a rectus sheath. The anterior abdominal wall is supplied by the anterior rami of the lower six thoracic and the first lumbar nerves. Some paraumbilical veins connect through the ligamentum teres to the portal vein, which is one of the sites of portosystemic anastomosis.

Posterior abdominal wall

The posterior abdominal walls are made up of the lumbar vertebrae with their intervertebral discs, twelfth ribs, upper part of the iliac bones, psoas major, quadratus lumborum, iliacus and origin of transversus abdominis.

Inguinal canal

There are two oblique passages, one on each side, in the lower abdomen, known as the inguinal canal. These canals transmit the spermatic cord in males and the round ligament in females, along with the ilioinguinal nerve and genital branch of the genitofemoral nerve in both sexes. 

The inguinal canal is bordered by the aponeurosis of the external oblique and internal oblique muscle anteriorly; transversal fascia posteriorly; transversal fascia, internal oblique and transversus abdominis superiorly; and the inguinal ligament and lacunar ligament inferiorly. 

Peritoneum

The peritoneum is a double membrane covering the abdomen, pelvis, and the organs within. It is divided into parietal layer and visceral layers. The parietal layer lines the cavity of the abdomen and pelvis, while the visceral layer covers the intraabdominal and intrapelvic organs. 

The space between the two layers is called the peritoneal cavity and is further divided into the greater sac and a lesser sac. These two parts of the peritoneal cavity interconnect via epiploic foramen. The greater sac is the main compartment, while the lesser sac is small and sits behind the stomach.

The parietal layer is sensitive to touch, temperature, pressure and pain, while the visceral layer is sensitive to stretch.

References

Wineski, L. E., & Snell, R. S. (2019). Snell’s clinical anatomy by regions. 

Chaurasia, B. D. (2019). Human anatomy: Regional and applied, dissection and clinical. New Delhi, India: CBS Publishers & Distributors.

Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Moore’s Clinically Orientated Anatomy (7th ed.). China: Lippincott.