Inguinal Canal – Abdominal Walls and Inguinal Canal

by Craig Canby, PhD

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    00:01 Next, we will take a moment to understand the inguinal canal and the features that you see to your left, the inguinal ligament, the superficial inguinal ring, lateral crus, medial crus and inner crura fibers are all demonstrable on this particular illustration.

    00:21 The inguinal ligament is the inferior most aspect of the aponeurosis of the external abdominal oblique and we see that inferior margin running along here. It attaches laterally and superiorly to the anterior superior iliac spine and then its medial inferior attachment would be to the pubic tubercle.

    00:44 In this medial location, along this region, we see an opening within the aponeurosis.

    00:52 This happens to be the superficial inguinal ring, and on the medial side of that, we have a medial crus, and on the lateral side, we have a lateral crus and then we have these interdigitating fibers interconnecting those two crura and those are the intercrual fibers.

    01:14 In a man, the major structure that we see here travelling out through the superficial inguinal ring is the spermatic cord. The spermatic cord enters this region by passing internally through a deep inguinal ring and as it travels through the inguinal canal, it will pick up all the layers that we see eventually emerging through the superficial inguinal ring.

    01:44 When we think about the inguinal canal, the inguinal canal will present two walls. It will also have a roof and it will also have a floor. So, what we want to do now is to explore the components that form the anterior wall, the posterior wall, the roof as well as the floor.

    02:07 Using the same image as the previous slide, our focus here is on the anterior wall and the anterior wall has been reflected so we are looking into the inguinal canal itself.

    02:20 So, let’s take a quick look at some of the landmarks here.

    02:25 This is your deep inguinal ring and you see some vascular structures passing through the deep inguinal ring. This muscular structure that we see here, in a man, is the ductus deferens. So, it passes through the deep inguinal ring and is now travelling within the inguinal canal and then it passes through the superficial inguinal ring at this particular location.

    02:51 The anterior wall has been reflected, contributing structure to the anterior wall is the aponeurosis of the external abdominal oblique which we see in through here and there is also going to be a lateral reinforcement from the internal abdominal oblique muscle.

    03:11 So, right in through here, and this would be the lateral most aspect of your canal, it too has been reflected away from the canal. The posterior wall is that area that we see in this general vicinity. The fascial component that we see that would pass behind the spermatic cord content that we see at this level is the fascia of the transversus abdominis. This is referred to, simply and aptly, as the transversalis fascia. More medially here along the posterior wall and not visible at this particular point in time, is a tendon referred to as the conjoined tendon. It is formed by the aponeurosis of the internal abdominal oblique as well as the transversus abdominis. So, that helps to reinforce the medial third dorsal at the posterior wall.

    04:14 The roof of the canal has been opened up. So, we are looking down into the canal yet again, but the roof of the canal would be formed in part by your internal abdominal oblique which is reflected here and then your transversus abdominis that we see at this level.

    04:40 And then lastly, we will have the floor to the inguinal canal. A good portion of the floor will be formed by the inguinal ligament. As that inguinal ligament approaches its medial attachment to the pubic tubercle, there will be an expansion of the inguinal ligament that will run more posteriorly to attach to the pectineal line of the superior ramus of the pubic bone. This expansion of the inguinal ligament more medially forms what is known as the lacunar ligament, so it will contribute to the floor as well.

    05:21 Again, there is some additional geometry that we can learn about in the discipline of anatomy and the inguinal region is no exception to that. Here, we are looking at the inguinal triangle also known as the triangle of Hesselbach. This triangle is bounded inferiorly by the inguinal ligament which is running right along here. So, that would actually form the base of our triangle. Another portion or boundary to our triangle is the lateral margin of the rectus abdominis that we see along here. And then this boundary or border to the triangle is formed by the inferior epigastric vessels. So, again, we have a nice geometric triangle formed by those three structures.

    06:22 Understanding the inguinal triangle is useful in one, understanding the difference between a direct and an indirect inguinal hernia. Here, we have herniation of intestinal loops into the scrotum. This is more common in men, but we can have an inguinal hernia occurring in women. The difference between a direct and an indirect is the relationship that the intestinal loop will take enter the scrotum.

    07:00 In the profile or image slide here on our right we have in reference, we have our inferior epigastric vessels, the artery as well as the vein. And here, we can see herniation of an intestinal loop into the scrotum and it takes a direct route into the scrotum because it passes medial to your inferior epigastric vessels.

    07:29 The left side of the image shows an indirect hernia. Here, the intestinal loop is passing lateral to those inferior epigastric vessels. Therefore, it will pass into the inguinal canal and it will have to exit at the level of the superficial inguinal ring which is at this general location and then once it passes through the superficial inguinal ring, it can then herniate into the scrotum.

    08:05 That now brings us to the important take-home messages from this presentation.

    08:11 First, the muscles of the abdominal wall are innervated by anterior rami from levels T7 all the way down through L4.

    08:24 Collectively, attachments are through the thoracic cage, pelvis and femur.

    08:32 Anterolateral muscles compress the abdominal viscera and function in lateral flexion and rotation.

    08:39 The most powerful muscles of the posterior abdominal wall, psoas major and iliacus, flex the thigh.

    08:48 The inguinal canal is a potential point of weakness allowing for direct or indirect herniation of intestinal contents.

    08:57 The inguinal triangle is bounded by the inguinal ligament, inferior epigastric vessels and the lateral margin of the rectus abdominis.

    09:08 And lastly, direct hernias pass medial to the inferior epigastric vessels whereas indirect hernias will pass lateral to that vasculature bundle.

    09:22 Thank you for joining me on this lecture on the muscles of the abdominal wall as well as its vasculature and innervation.

    About the Lecture

    The lecture Inguinal Canal – Abdominal Walls and Inguinal Canal by Craig Canby, PhD is from the course Abdominal Wall.

    Included Quiz Questions

    1. Rectus abdominis muscle
    2. Transversus abdominis muscle
    3. Inguinal ligament
    4. Inferior epigastric vessels
    5. Internal oblique muscle
    1. External oblique muscle
    2. Internal oblique muscle
    3. Transversus abdominis muscle
    4. Rectus muscles
    5. Iliopsoas muscle
    1. Spermatic cord
    2. Round ligament
    3. Broad ligament
    4. Lymphatics
    5. Femoral artery
    1. Internal oblique muscle
    2. External oblique muscle
    3. Rectus muscle
    4. Transversus abdominus muscle
    1. Lateral border of the rectus sheath
    2. Superior epigastric vessels
    3. Medial border of the rectus sheath
    4. Femoral artery
    5. Inferior epigastric vessels
    1. Direct inguinal hernia
    2. Indirect inguinal hernia
    3. Femoral hernia
    4. Umbilical hernia
    5. Supraumbilical hernia

    Author of lecture Inguinal Canal – Abdominal Walls and Inguinal Canal

     Craig Canby, PhD

    Craig Canby, PhD

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    good lecture overall
    By Edward K. on 27. August 2017 for Inguinal Canal – Abdominal Walls and Inguinal Canal

    good lecture- lost a star because illustrations are in latin. I do appreciate latin is completely acceptable to use in the context of anatomy, but in practice nobody uses latin terms and it feels outdated and counter-productive to learn the latin nomenclature. It would be much easier to follow if everything was in english ; a small point but it did slow me down when following this lecture.