Posterior abdominal wall

From IKE
Jump to: navigation, search

The posterior abdominal wall is the back wall of the abdominal cavity. It is formed centrally by the five lumbar vertebrae and related structures. Lateral to the vertebral column, on each side, is a paravertebral gutter, which is formed, from above-down, by the diaphragm, psoas and quadratus lumborum muscles, and the iliac crests and iliac fossae, containing the iliacus muscles.

Muscles

All three muscles are covered by fascia, named after the muscles related to it, which is derived from the transversalis fascia. Superiorly, the quadratus lumborum fascia forms a linear thickening known as the lateral arcuate ligament (between the L1 transverse process and 12th rib). Similarly, the psoas fascia is thickened superiorly, to form the medial arcuate ligament (between the L1 vertebra and its transverse process). Both ligaments provide attachment for the diaphragm.

Vessels

The two major vessels of the abdomen are the abdominal aorta and the inferior vena cava.

Lymphatics

  • Preaortic nodes
    • lie in front of the aorta at the origin of the celiac, superior mesenteric and inferior mesenteric arteries
    • Their efferents join the intestinal lymph trunk
  • Paraaortic nodes
    • also known as lateral aortic or lumbar nodes
    • are arranged in a right and a left chain on each side of the abdominal aorta
    • They receive lymphatic drainage from:
      1. the common iliac nodes,
      2. the abdominal wall and diaphragm,
      3. kidneys and suprarenal glands,
      4. the ovaries and testes
    • Their lymph is channelled through the right and left lumbar lymph trunks.

Another important lymphatic structure is the cisterna chyli.

Innervation

Sympathetic ganglia

  • The lumbar sympathetic trunks and ganglia are continuations of the thoracic sympathetic trunks
  • They enter the abdomen behind the medial arcuate ligament to descend on the sides of the lumbar vertebral bodies
  • The right trunk lies behind the inferior vena cava and the left runs lateral to and slightly behind the aorta
  • Inferiorly, they are continuous below with the sacral sympathetic trunks
  • The lumbar ganglia are often fused and their number varies from two to four on each side
  • Grey rami communicantes are given off from all ganglia to the five lumbar spinal nerves
  • Lumbar splanchnic nerves, arising from the lumbar sympathetic ganglia, convey preganglionic visceral efferents to the plexuses associated with the aorta

Lumbar plexus

  • primary ventral rami of five lumbar nerves and of first four sacral nerves combine to form the lumbar (L1, L2, L3, L4) & lumbosacral (L4, L5, S1, S2, S3, S4) plexuses, each giving rise to anterior and posterior branches
  • anterior branches supply flexor muscles of limb, while posterior branches supply extensor and abductor muscles
  • largest of these derivatives are femoral & obturator nerve [1]

Objectives

  • name the skeletal components of the posterior abdominal wall
  • name the muscles of the posterior abdominal wall and state their functions
  • describe the structure of the diaphragm and list its attachments
  • state the innervation and blood supply of the diaphragm
  • list the main openings in the diaphragm, their vertebral levels and the structures passing through them
  • describe the course of the abdominal aorta. List its main relations and its branches
  • describe the course of the inferior vena cava and list its main relations and its tributaries
  • name the main groups of lymph nodes related to the abdominal aorta and its branches
  • describe the cisterna chyli and list its main afferent lymph channels
  • outline the arrangement of sympathetic ganglia and autonomic plexuses as they relate to the posterior abdominal wall
  • define the term "lumbar plexus", list its main branches and outline their functions and territory of supply.