[0:20]Good morning. This is Dr. Adel Bondok, Professor of Anatomy and Neuroscience, Mansoura University, Egypt. Today I will talk about the Rectus Sheath. I will talk about the walls, the contents, and the paramedian abdominal incision. So I will talk about the walls and the contents. Regarding the walls, the rectus sheath is divided into three levels. Level one is above the costal margin. Level two is above the arcuate line between the costal margin and mid-point between the umbilicus and the pubis symphysis. And level three below the arcuate line, between the mid-point between the umbilicus and symphysis pubis and the symphysis pubis. So we have three levels, above the costal margin, above the arcuate line, and below the arcuate line. And this is the level of the arcuate line. Regarding the contents, the rectus sheath contains two muscles: rectus abdominis muscle and pyramidis. This is the pyramidis muscle, two blood vessels, superior epigastric vessels and inferior epigastric vessels, and nerves lower six thoracic nerves or lower five intercostal and subcostal nerves. The vessels and the nerves are located behind the rectus muscle. So you don't see the vessels and the nerves here because they are located behind the muscles. Let us talk about the three levels of the rectus sheath. Level one above the costal margin. So I will talk about the anterior wall and the posterior wall. The anterior wall above the costal margin is the external oblique aponeurosis only. The posterior wall actually is deficient. The rectus muscle lies directly on the costal cartilages number five, number six, and number seven. So above the costal margin, the anterior wall of the rectus sheath is the external oblique aponeurosis. The posterior wall of the rectus sheath is the fifth, sixth and seventh costal cartilages. Level two above the arcuate line. This is the arcuate line, which is the lower border of the internal oblique and transversus abdominis aponeurosis. So level two, between the costal margin and mid-point between umbilicus and symphysis pubis. This is the real rectus sheath. The anterior wall is formed of two layers and the posterior wall is also formed of two layers. The anterior wall is formed of external oblique aponeurosis and the anterior layer of the internal oblique aponeurosis. This is the internal oblique. The posterior wall is formed of the posterior layer of internal oblique aponeurosis and transversus abdominis aponeurosis. These are the three muscles of the anterior abdominal wall: external oblique, internal oblique and transversus abdominis muscle. So again, rectus sheath between the costal margin and arcuate line or above arcuate line. Anterior wall two layers, external oblique aponeurosis and anterior layer of internal oblique aponeurosis. Posterior wall is also formed of two layers, posterior layer of internal oblique aponeurosis and transversus abdominis aponeurosis. Then level three, level three below the arcuate line. Below the arcuate line, below the aponeurosis of the internal oblique and transversus abdominis muscle. This is the transversalis fascia, this one. So level three, the anterior wall is formed of the aponeurosis of the three muscles. So this is the anterior wall, external oblique aponeurosis, transversus abdominis aponeurosis and sorry internal oblique aponeurosis and transversus abdominis aponeurosis. The posterior wall of the rectus sheath is formed only by transversalis fascia. This is the transversalis fascia. Okay. Regarding the contents of the rectus sheath. This is the rectus sheath open. Okay. It contains two muscles. The two muscles are rectus abdominis muscle and pyramidalis muscle. Then two vessels or two arteries. The two vessels are superior epigastric vessels and inferior epigastric vessels. And then nerves. The nerves are lower six thoracic nerves or lower five intercostal nerves and the subcostal nerve. The vessels and nerves are located behind the rectus muscle. So again, just a summary. Regarding the walls, above the costal margin. Anterior wall, external oblique aponeurosis. Posterior wall, costal cartilages number five, number six and number seven. Then level two above the arcuate line. Anterior wall is the external oblique aponeurosis and anterior layer of internal oblique aponeurosis. Posterior wall is the posterior layer of internal oblique aponeurosis and transversus abdominis aponeurosis. Then level three, this is level three, below the arcuate line. This is the arcuate line. Level three anterior wall is the aponeurosis of the three muscles. External oblique, internal oblique and transversus abdominis. The posterior layer is formed only by this fascia, which is the transversalis fascia. Regarding the contents, two muscles, rectus abdominis muscle and this small muscle, pyramidalis muscle. Then two vessels, superior epigastric vessels and inferior epigastric vessels. And they are located behind the rectus muscle. And then lower six thoracic nerves. Regarding the paramedian abdominal incision. This is the paramedian abdominal incision. In paramedian abdominal incision, because the nerves enter the rectus sheath from the lateral side, after opening the anterior wall of the rectus sheath, the rectus muscle should be retracted laterally to avoid injury of the thoracic nerves.
[7:26]Again, in paramedian abdominal incision, the anterior wall of the rectus sheath is opened. And after opening the anterior wall, the rectus abdominis muscle is retracted laterally. And then the posterior wall is opened. It is retracted laterally to avoid injury of the intercostal nerves which enter the rectus sheath from the lateral side. And thank you very much. Best wishes and good luck.
