Internal Oblique and Transversus Abdominis

00:01 The next muscle we'll look at is internal oblique.

00:04 And that is situated deep to external oblique.

00:07 If you remember from the previous slides.

00:09 An internal oblique has a large number of bony attachments, origins, and insertions.

00:15 So we can see those on the screen here.

00:17 So most posteriorly we see on the left hand side of the screen there.

00:21 We have the thoracolumbar fascia, we also have the anterior aspect of the iliac crest, and the lateral third of the inguinal ligament.

00:28 And these are all areas where internal oblique muscle originates from.

00:33 And you can see by the direction of the arrows, it's moving up towards the ribs and cartilages 10 through to 12.

00:40 So again, there may be some variation in depending on the textbooks you have.

00:44 But typically, the internal oblique muscle will insert onto the ribs and the costal cartilages of ribs 10 to 12.

00:53 You can see it actually passes up by these green dots.

00:56 And it doesn't necessarily run perpendicular to external oblique, the upper fibers which you can see running upwards, those very much do run perpendicular to external oblique.

01:07 But as we go to the inferior aspect of the muscle belly, you can see those fibers, importantly curve anteriorly and curved towards the pubic tubercle.

01:18 And we'll come to that in more detail later on when we look at the inguinal region.

01:22 Similar to external oblique, the muscle of internal oblique gives rise to a thin tenderness flat sheath and this is the aponeurosis.

01:31 So again, we can see the aponeurosis here of internal oblique is running towards the midline, where we have the linea alba.

01:38 And this forms an important union with the aponeurosis of external oblique.

01:43 And again, we'll come to that in a moment or two.

01:46 The function of internal oblique is again to help with bending of the trunk.

01:50 You can see on the screen at the moment, so the left and the right aspects of internal oblique will help with that left and right bending.

01:58 Again, they help to compress the abdominal contents help them to maintain possession.

02:02 And also when both of the internal oblique muscles contract so you'll have flexion of the trunk.

02:09 The third of these lateral muscles that we want to talk about is transversus abdominis.

02:15 As you can see on a similar diagram, the origins and insertions of the transverse abdominis muscle are similar coming from similar regions that we've already seen.

02:24 So posteriorly, we have the thoracolumbar fascia, we have the iliac crest, inferiorly, and then superiorly, we have the inner surface of now 7 through to 12, costal cartilages.

02:36 So we can see we have the origins of that muscle.

02:39 This time, as we spin it round to the anterior aspects, let's just do that slightly. Again, you can see the green arrows are really indicating the transverse nature of this muscle.

02:49 A reason I haven't indicated because we can see it now as it rotates is that these muscle also goes on to the lateral third of the inguinal ligament, and we'll come back to that later on.

03:00 So it's good to see that transverse nature of this muscle transverse abdominis, as it causes around anteriorly onto the abdominal wall.

03:09 But you can see now how it runs anteriorly towards the midline, where again, it unites with the linea alba.

03:16 And again, those green arrows are indicating the aponeurosis of this transverse abdominis muscle.

03:22 So here we can see the linear alba.

03:26 The function of this muscle very similar to what we've seen before compression of abdominal contents.

03:31 And it can also help when those muscles contract to helpfully rotate the abdomen as round as well.

03:36 So out rotate the trunk.