Lectures

Rectus Sheath I – Anterolateral Abdominal Wall

by James Pickering, PhD
(1)

Questions about the lecture
My Notes
  • Required.
Save Cancel
    Learning Material 2
    • PDF
      Slides 02 Abdominal and Pelvic Anatomy Pickering.pdf
    • PDF
      Download Lecture Overview
    Report mistake
    Transcript

    00:01 Now, aponeurosis are really important. They are just like a tendon, like your biceps attaches to your radius in your arm. They are very thin and quite strong tendon. But, for these anterolateral abdominal wall muscles, the tendon is only flat and forms a kind of fibrous sheath and these are known as aponeurosis. And these aponeurosis form what?s called the rectus sheath. And on the body plan, we can remember that we have got the midline running down here and then we have got our semilunar lines. Remember, those semilunar lines from the surface anatomy talk. Well, these semilunar lines form the lateral boundary of a structure known as the rectus sheath. We can see them here where we have got the midline and we can make out the indentations of rectus abdominis and then we have the semilunar lines here. And these form the boundaries of what?s known as the rectus sheath.

    00:59 This is formed by the aponeurosis from these muscles coming around and interdigitating around rectus abdominis to unite in the midline and we can see this here. Now, this is a particularly complicated image. So, I have to take some time in explaining it, but what we can see is a transverse section through the abdomen. So, it?s like someone?s just chopped me in half and you are looking down on to the cut surface.

    01:31 So, we can see, what we have is the posterior aspect which is down here. So, this is your back and then here, this is anteriorly here. So, that?s where your umbilicus is.

    01:45 This is in the midline here. So, this is where your linea alba is going to be located.

    01:50 And what we have radiating from the posterior aspect of these anterolateral abdominal wall muscles, we can see we have three of them again. We have 1, 2, 3. We have our external oblique, internal oblique and transversus abdominis. We have got these three muscles. But, what you notice is the actual muscle tissue which is here in orange, doesn?t run all the way to the midline. The musculature stops just before it gets to the rectus abdominis muscle here. So, this is where we find our semilunar lines, just here, the lateral extension or the lateral boundary of the rectus sheath, of rectus abdominis muscle here. And what we find is that these aponeurosis from muscles external oblique, internal oblique and transversus abdominis interdigitate around rectus abdominis as they pass towards the linea alba in the midline. The formation of the rectus sheath differs and this is where above and below comes in. It differs, if you are above or below the umbilicus. Now, this is the level of the umbilicus, this here. This is the umbilicus just here. So, if you are above the umbilicus or if you are below the umbilicus, this arrangement is going to be different.

    03:21 So, let's have a look. If we are above the umbilicus, we are looking at the details now of the rectus sheath above the umbilicus and that?s this one here. So, imagine that this line here is coming... just like this one, coming from the posterior aspect. So, it?s taken higher up above the umbilicus. We are looking at the formation of the rectus sheath.

    03:45 We can see that here we have external oblique, here we have internal oblique and here we have transversus abdominis. We can see the anterior... this is the rectus sheath anteriorly, we have the aponeurosis of external oblique and posteriorly, behind rectus abdominis, we have the aponeurosis of transversus abdominis. So, anteriorly to the rectus abdominis muscle, we have the aponeurosis of external oblique and posterior to rectus abdominis, we have the aponeurosis of transversus abdominis. So, what happens to internal oblique? Well, the internal oblique muscle, as it approaches rectus abdominis, splits into two.

    04:38 So, the aponeurosis of internal oblique splits into two lamina, an anterior lamina and a posterior lamina. So, we have the anterior layer of internal oblique aponeurosis.

    04:52 Posteriorly, behind rectus abdominis, internal oblique sends a layer that goes behind rectus abdominis.

    05:02 So, posterior, we have the posterior layer of internal oblique aponeurosis.

    05:08 So, if we were to go from anterior to posterior, we would find the aponeurosis of external oblique.

    05:15 We?d then find the anterior lamina or the anterior layer of internal oblique, we?d then find rectus abdominis. Carrying on posterior, we?d then have the posterior lamina or layer of internal oblique and then we would have the aponeurosis of transversus abdominis.

    05:37 So, effectively would have one and a half anteriorly and one and a half posteriorly where the two halves have come from internal oblique dividing. And then most posterior, we then have a fine layer which is called transversalis fascia and then we have the peritoneum. We will explore those in later classes, in later lectures. So, that?s above the umbilicus.

    06:00 If we now go below the umbilicus... If we now go below the umbilicus, then this is a lot simpler. So, previously, we had the section above and now, we have made a section below the umbilicus. So, now, we are concentrating on this one. Similar orientation of muscles.

    06:19 Here, we have got rectus abdominis radiating around here. We are mentioning that this is attaching to the posterior wall again, so a similar arrangement, but this time, the aponeurosis from all three anterolateral abdominal wall muscles, all three, external oblique, internal oblique, transversus abdominis, runs anteriorly. Internal oblique doesn?t split and transversus abdominis aponeurosis passes anterior to rectus abdominis.

    06:53 So, the only thing we have posterior to rectus abdominis is that membrane I spoke about, transversalis fascia, and then the peritoneum. We can see it here. External oblique, internal oblique, transversus abdominis. We can see that the aponeurosis from these muscles all pass anterior to rectus abdominis. So, we can see that above and below the umbilicus, the rectus sheath is very different. Above it, internal oblique is divided, lamina goes anterior and lamina goes posterior and below the umbilicus, all three aponeurosis pass anterior to rectus abdominis to then merge with the linea alba. So, that?s the rectus sheath. It?s a very, very important arrangement.


    About the Lecture

    The lecture Rectus Sheath I – Anterolateral Abdominal Wall by James Pickering, PhD is from the course Abdomen.


    Included Quiz Questions

    1. ...transversus abdominis and internal oblique aponeurosis.
    2. ...transversus abdominis aponeurosis only.
    3. ...transversus abdominis aponeurosis and transversalis fascia.
    4. ...transversus abdominis and external oblique aponeurosis only.
    1. Aponeurosis of transversus abdominis.
    2. External oblique muscle.
    3. Anterior lamina of internal oblique muscle.
    4. Lower six pair of ribs.
    5. Rectus abdominis muscle.
    1. Rectus abdominis.
    2. External oblique.
    3. Transversus abdominis.
    4. Inguinal ligament.
    5. Linea alba.
    1. External oblique, internal oblique and transversus abdominis.
    2. External oblique, anterior lamina of internal oblique muscle and rectus abdominis.
    3. External oblique, posterior lamina of internal oblique muscle and rectus abdominis.
    4. External oblique, rectus abdominis and internal oblique.
    5. External oblique, transversus abdominis and internal oblique.

    Author of lecture Rectus Sheath I – Anterolateral Abdominal Wall

     James Pickering, PhD

    James Pickering, PhD


    Customer reviews

    (1)
    5,0 of 5 stars
    5 Stars
    1
    4 Stars
    0
    3 Stars
    0
    2 Stars
    0
    1  Star
    0
     
    Very well explained. I never understood abdominal wall that much. I wish you did all the courses
    By sabi y. on 08. April 2018 for Rectus Sheath I – Anterolateral Abdominal Wall

    This is the best explanation. Thanks Doctor James. I can t stop watching it again and again.