Posterior abdominal wall
This specimen shows the muscles and the nerves of the posterior abdominal wall.
The posterior abdominal wall presents three important muscles, namely, the psoas major, the quadratus lumborum and the transversus abdominis. The nerves arising from the lumbar plexus, such as, the Iliohypogastric nerve, the Ilioinguinal nerve, the lateral cutaneous nerve of the thigh and the femoral nerve are seen arising around the psoas major muscle. Other structures such as the diaphragm, the Abdominal aorta, the inferior venacava can be seen in the specimen.
The diaphragm forms a musculo-aponeurotic partition between the thorax and the abdomen. It has its origin from the xiphoid process of the sternum, the lower six ribs and the upper lumbar vertebrae. The insertion lies at the central tendon. It has major and minor openings that allow the passage of structures between the two parts. It is a very important muscle of respiration. It is supplied by the phrenic nerve. It allows the passage of the structures between the two parts.
The psoas major muscle takes origin from the lumbar vertebrae and insert into the lesser trochanter of femur. It is supplied by the lumbar spinal nerves. It is known to be the key muscle of the posterior abdominal wall. The lumbar plexus of nerves is formed within the muscle.
The quadratus lumborum muscle takes origin from the iliac crest of the hip bone and inserts into the twelfth rib. It is supplied by the thoracic and lumbar spinal nerves.
The transversus abdominis is the innermost muscle of the anterior abdominal wall. The fibres are directed transversely. Its aponeurosis forms the rectus sheath and also presents the deep inguinal ring for the passage of the spermatic cord.
The iliohypogastric nerve is a branch of the lumbar plexus. Its root value is L1.
The ilioinguinal nerve is a branch of the lumbar plexus. Its root value is L1.
Lateral cutaneous nerve of the thigh:
The lateral cutaneous nerve of the thigh enters the thigh by passing deep to the inguinal ligament to supply the skin of the upper lateral aspect of the thigh. Its root value is L2 and L3.
The femoral nerve emerges along the lateral aspect of the psoas major. It passes deep to the inguinal ligament to supply the structures of the lower limb. Its root value of dorsal divisions of ventral rami of L2, L3 and L4.