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Inguinal Canal – Inguinal Region

by James Pickering, PhD
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    00:01 So, if we remember the musculature that we spoke about in the previous lecture, we remember here, which we can see those from anterior to posterior, here we can see the piece of intestine, piece of gastrointestinal viscera and from anterior to posterior, we can see the skin, we can see those three layers of muscles, we can see external oblique, we can see internal oblique and we can see transversus abdominis. And then we mentioned thin membrane called transversalis fascia and for the inguinal canal, this is a really important membrane.

    00:39 So, please remember we have external, internal oblique, transversus abdominis and transversalis fascia in that order from anterior to posterior or from deep to superficial. And here, we can see them with some details on the side of the screen. Here we can see external oblique's aponeurosis, we can see external oblique, the fibers... the fibers running down in this direction, we can see its fibers running towards the linea alba in the midline. We can also see that we have got a slight defect here in external oblique's aponeurosis. We have a slight defect and that defect, this opening is known as the superficial inguinal ring.

    01:28 So, here, we have got external oblique's aponeurosis and I can just draw out, just make out a line here and this is external oblique aponeurosis with a defect in and this is the superficial inguinal ring. It’s within external oblique's aponeurosis and it’s really important because it allows the spermatic cord or the round ligament of the uterus in the female to leave the abdomen, so allows these structures to pass away from the abdomen and go the labia majora in the female or go to the scrotum in the male. We can see we have got a superficial inguinal ring down here, we also have a deep inguinal ring and we will explore that later on.

    02:16 These muscles which I spoke about previously, they still exist in this inguinal region and they go on to form what’s known as the inguinal canal. This is a canal that has four boundaries, it has an anterior wall which we will look at and for now, we can say that is the external oblique aponeurosis. We can see that here, the anterior boundary. We will explore later and see the other structures also from the anterior boundary. It has a posterior wall and this is where we need to remember transversalis fascia, it has a floor which is the inguinal ligament, we can see that here, the inguinal ligament and then it has a roof and this is really important because the roof is formed from some arching fibers that start from the inguinal ligament and then run medially and posteriorly to attach to the pubic tubercle and by doing that, they create a channel that allows the spermatic cord or the round ligament of the uterus to pass through. So, it’s particularly complicated, this area. So, it’s important to try and listen carefully and try and appreciate the nuances of these... of this arrangement. So, this diagram, which we can see, tries to explain the arrangement of the inguinal canal and like I said, it’s particularly complicated, but let’s just try and remind ourselves of some basic information that we already know.

    03:52 We know we have three layers of muscles. We have got external oblique which we can see here, we have got internal oblique and then deepest, we have got transversus abdominis.

    04:04 Now, it’s important to remember those structures, those muscle layers. We can also see that we have a whole series of structures here which are starting within the abdomen and this is really quite clear if you imagine the male, where the testes of the male are positioned outside of the abdominal cavity, they are located within the scrotum. And here, we can see we have got the testes. But, during development, these testes and the ovaries originated on the posterior abdominal wall, but with development, they migrated down the posterior abdominal wall and penetrated the anterior abdominal wall to reside in the scrotum. The ovaries didn’t, the ovaries stayed in the pelvis which we will see as we go on to the pelvis in future lectures, but the testes migrated through the anterior abdominal wall. So, as they migrated through the anterior abdominal wall, they took with them the layers of the muscles that formed the anterior abdominal wall.

    05:12 So, if we look in more detail, we can see that these structures that are passing down in this direction, they head towards the anterior abdominal wall and then they pass through the wall to exit via the superficial inguinal ring which we can see here. And on this side of the screen, we can see that I have put in some details which help to work out how to explain the arrangement and the formation of the inguinal canal.

    05:48 So, what we can see is the free edge of external oblique aponeurosis. External oblique, we see muscle here is running down in this direction. Remember, it’s running downwards and forwards.

    05:59 And this muscle runs to where we have got the anterior superior iliac spine here and it runs all the way down to where the pubic tubercle is here. And at the free edge, so, this boundary here, this inferior boundary of external oblique aponeurosis is the inguinal ligament. A sheath of muscle that is coming down gives right to its aponeurosis and where it attaches to the pubic tubercle and the anterior superior iliac spine, it kind of turns back on itself to create a gutter, that is the inguinal ligament. Well, we can see on numerous layers, here we have got transversalis fascia and here, again, we can see transversus abdominis and then we can see internal oblique. And what we can see is if we imagine this teste has started up here, the teste has migrated down through these layers.

    06:59 It’s migrated down through these layers. So, it’s passed down in this direction.

    07:07 So, as it has passed down, it’s taken a layer of transversalis fascia with it, okay? So, transversalis fascia is lining the posterior abdominal wall and as the teste has gone through it, it’s taken a layer with it. So, it’s pushed through this membrane, much like when you put your finger inside a balloon, it takes a layer of that balloon covering with it and that’s what’s happened. It’s passed all the way through with a layer of transversalis fascia. We can also see that it’s gone underneath this muscle here and this muscle, if we follow it back, is transversus abdominis. Importantly, transversus abdominis runs horizontal. From the inguinal ligament, it runs horizontally across. So, the testes hasn’t actually penetrated transversus abdominis, like it passes through transversalis fascia taking a layer with it. It actually runs underneath transversus abdominis muscle and that’s where we can see transversus abdominis arching over, forming the roof of the inguinal ligament.

    08:24 We can also see that we have this muscle layer here, this is internal oblique and we can see actually that the testes has taken with it, a layer of internal oblique. So, it actually went through, just like transversalis fascia, it went through internal oblique taking a layer with it. Also, we can see parts of internal oblique running over the spermatic cord.

    08:51 So, we have a second structure forming its roof. We have transversus abdominis here and now, we have internal oblique. These structures are forming the roof. If we look anterior to the spermatic cord, which contains the tail of the testes with the vas deference and various blood vessels within it, we can see that anterior to it, we actually have external oblique aponeurosis and internal oblique muscle. So, that forms the anterior wall.

    09:27 The floor, we said, is the inguinal ligament. Anteriorly, we have got external oblique aponeurosis and internal oblique aponeurosis. Over the roof, we have got transversus abdominis and we have got internal oblique. And then posteriorly, we can see we have this thin membrane which the testes penetrated as they passed through and that’s transversalis fascia forming the posterior boundary.

    09:57 Now, these structures vary subtly as we are going from the lateral to the medial aspects of the inguinal canal and they vary depending on exactly where you are in the inguinal canal.

    10:10 But, that paints a general picture that is probably sufficient for the majority of you to understand that we have these layers that the teste passes through. I haven’t mentioned the deep inguinal ring, but we can see the deep inguinal ring is here and that really is where the testes have penetrated through transversalis fascia to enter into the canal.

    10:35 So, we can see the deep inguinal ring is starting here. Importantly, we have inferior epigastric vessels lying medial to it. So, the deep inguinal ring runs around, runs lateral to the structures in the deep inguinal ring run lateral to these epigastric blood vessels. That’s really important when you are using an ultrasound to locate inguinal hernias. And then the deep inguinal ring contains a spermatic cord or the round ligament of the uterus passes out through this defect in external oblique and that is the superficial inguinal ring and here, we can see the testes. One more detail on the posterior wall. I mentioned this mostly formed by a transversalis fascia, but we can also see really clearly in this diagram, the conjoint tendon. The conjoint tendon is really important. It lies directly posterior to the superficial inguinal ring and it’s formed by internal oblique aponeurosis and transversus abdominis aponeurosis merging together where these two muscles merge together to attach onto the pubic tubercle and this conjoint tendon is really important as it helps to strengthen the inguinal canal directly posterior to the superficial inguinal ring. If you can imagine that we have got this slit like opening in external oblique aponeurosis, the superficial inguinal ring. Then this is a potential site of weakness. So, increases in intra abdominal pressure can push against this weakness and it may herniate. The conjoint tendon re-enforces this posterior boundary of the superficial inguinal ring helping to prevent herniation.

    12:25 So, here we have a nice diagram showing an overview of the inguinal canal, but I appreciate this region is particularly tricky. So, we have got a table here which summarises what


    About the Lecture

    The lecture Inguinal Canal – Inguinal Region by James Pickering, PhD is from the course Abdomen.


    Included Quiz Questions

    1. ...the internal oblique and transversus abdominis aponeuroses.
    2. ...the external oblique and transversus abdominis aponeuroses.
    3. ...the transversus abdominis aponeurosis and the transversalis fascia.
    4. ...the internal oblique aponeurosis and the transversalis fascia.
    1. external oblique
    2. internal oblique
    3. transversalis fascia
    4. transversus abdominis
    1. inguinal ligament
    2. external oblique aponeurosis
    3. internal oblique aponeurosis
    4. transversus abdominis
    1. Ilioinguinal nerve
    2. Cremasteric artery
    3. Ductus deferens
    4. Genital branch of the genitofemoral nerve
    5. Testicular artery
    1. Occurs at the level of the superficial inguinal ring
    2. Occurs at the level of the deep inguinal ring
    3. Exits the abdomen lateral to the inferior epigastric vessels
    4. Is typically found in young men
    1. Deep inguinal ring lies lateral to inferior epigastric vessels.
    2. Deep inguinal ring lies medial to the inferior epigastric vessels.
    3. Deep inguinal ring lies posterior to inferior epigastric vessels.
    4. Deep inguinal ring lies superior to inferior epigastric vessels.
    5. Deep inguinal ring lies inferior to inferior epigastric vessels.
    1. External oblique aponeurosis.
    2. Internal oblique muscle.
    3. Transversus abdominis muscle.
    4. Transversalis fascia.
    5. Linea alba.
    1. Conjoint tendon.
    2. Internal oblique muscle.
    3. External oblique muscle.
    4. Transversus abdominis muscle.
    5. Rectus sheath.

    Author of lecture Inguinal Canal – Inguinal Region

     James Pickering, PhD

    James Pickering, PhD


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    Great help for review for exams
    By Jillian S. on 05. December 2017 for Inguinal Canal – Inguinal Region

    high yield review for finals and it's pretty direct and the important matters are stated.