The Rectus Sheath

Location

• Fibrous compartment for rectus abdominis muscle in the paramedian abdominal wall.s

Formation

• Formed of the aponeurosis of abdominal muscles.
  
  
• It has a posterior layer and anterior layer.

Proximal 1/3rd

• The anterior layer joins the aponeurosis of the external oblique to form the anterior wall of the rectus sheath.
  
  
• The posterior layer joins with the aponeurosis of the transversus abdominis to form the posterior wall of the rectus sheath.

Middle 1/3 rd

• Aponeurosis of internal oblique joins external oblique aponeurosis to form anterior wall.
  
• Posterior wall is formed by aponeurosis of transversus abdominis muscle

Distal 1/3 rd

• Mid way between umbilicus and pubic crest all three aponeurosis form the anterior layer
  
  
• The posterior layer is formed only by fascia transversalis

Note:

The anterior and posterior layers fuse in the midline to form the linear alba, a fibrous intersection extending from the xiphoid process to the pubic symphysis. The inferior ¼ of the rectus sheath is deficient posteriorly. The limit of the posterior wall is marked by the arcuate line The lateral margin of rectus sheath is called linea semilunaris

Contents of Rectus Sheath

• Rectus abdominis muscle
• Inferior and superior epigastric vessels
• Terminal parts of the lower five intercostal nerves, and the Subcostal nerve.
• Fibro fatty connective tissue
• Occasionally lymph node(s)

Extra peritoneal fascia

• Transparent ‘membrane' which lines the inside of the abdominal wall.
  
  
• Its parts are named according to what it lines e.g.
  
  (+) diaphragmatic fascia;
  (+) iliac fascia;
  (+) psoas fascia.
  (+) fascia transversalis ( part covering the muscle transversus abdominis ).