 One, two, three. Good day everybody. Dr. Sanjay Sanyal, Professor Department Chair. So this is going to be a demonstration of the lumber plexus originating from the lumber region abdomen. Pastry abdominal wall going all the way to the thigh. This is a supine cadaver. We are standing on the left side of the cadaver. The camera person is also on the left side. So just to bring up the speed, we have completely opened up the thorax on the abdomen. And this is the pastry abdominal wall. This muscle that we see here, this is the soas major muscle on the left side. This muscle that we see above here, this is the quadratus lumborum. And this is the ilio-lumbar ligament. And below that, this is the iliacus. So therefore, this is the combined ilio-soas, which is going to the thigh. So these are the muscles of the pastry abdominal wall. Now let's take a look at the nerves which are emerging from the lumber plexus. We can feel the 12th rib here. And we can see that the diaphragm is attached to that. And we can also see the quadratus lumborum is attached to that. So now which is emerging from just below the 12th rib is this one. This is the subcostal nerve, T12. This supplies the lower abdominal muscle. And after that, it also supplies the skin. The next nerve that we can see here is this one which I have lifted up here. This is L1. And the L1 divides into two branches. And we can see the two branches very clearly here. The upper one is the iliohypogastric and the iliohingual. The iliohypogastric supplies only the lower abdominal muscles, namely the transverse abdominis and the internal oblique in the region of the conjoint tendon. It does not go below the inguinal ligament. The iliohingual on the other hand. It also supplies the same two muscles. And it continues into the lower abdomen. And from there it continues into the inguinal region. And it supplies the skin of the upper medial thigh. And it also supplies the skin of the anterior aspect of the scrotum or the labia. Where it is known as the anterior scrotal nerve or the anterior labial nerve. So therefore the iliohingual goes through the inguinal canal. This iliohingual nerve, when it is cutaneous, it serves as the afferent limb of the cremaster reflex in young mage children, which I shall elaborate again a little later. Coming to the next nerve, we can see this nerve here. And I am going to lift this up. And when I pull here, I will draw your attention to below the inguinal ligament. So please watch carefully. We can see one nerve moving here. This is the lateral femoral cutaneous nerve, lateral cutaneous nerve of the thigh. This goes just under the inguinal ligament, close to its attachment to the anterior spinae. Close just under the attachment of the sartorius muscle. And we can see the nerve fibers coming here. And it supplies the skin of the anterior lateral aspect of the thigh. And this can get entrapped. When a person gains weight, it can get entrapped under the inguinal ligament. And that can lead to numbness, stinging, and peristhesia on the antrilateral aspect of the thigh. And that condition is referred to as meralgia peristhetica. So that is the next nerve that we can see here. Then I will draw your attention to this nerve. This is the one which is running on top of the soas major muscle. And we can see it is going here. This is the genitofemoral L12. It's got two components, a genitofemoral component and a femoral component. The femoral component supplies the skin of the upper anterior thigh a little bit. The genital component goes through the inguinal canalogate. It goes through the spermatic cord. And it supplies the cremaster muscle. And it also supplies the antrilateral scrotum. This genitofemoral nerve, the genital branch, supplies as the efferent limb of the cremaster reflex. What is this cremaster reflex? When we stroke the upper medial thigh skin in a young male child, it produces retraction of the testis into the inguinal canal by virtue of the contraction of the cremaster muscle. So that is the cremaster reflex. To continue, we can see the next nerve which is coming out from the lower lateral aspect of the soas major. And I will go under the soas major and I am going to reflect the soas major and we can see the other portion of the nerve here. This is L234 posterior division, the femoral nerve. And I am going to show you the continuation of the femoral nerve under the inguinal ligament. So my finger is going under the inguinal ligament. This is the inguinal ligament. And we can see the femoral nerve is going. And I am going to turn the inguinal ligament and we can see the rest of the femoral nerve here. So this is the femoral nerve coming into the thigh. And we can see the moment it comes into the thigh, it has got a very short segment in the thigh in the femoral triangle and it divides into hundreds of branches which supplies anterior compartment. The quadriceps muscles and the muscles of the anterior compartment and it also supplies the skin of a large portion of the anterior thigh as the anterior femoral cutaneous nerve. So therefore, if you watch carefully, when I exert traction here, we can see it is moving here. And we can also see it is moving here. So this is the femoral nerve, L234 posterior division. Again, to go back to where we started from, if you look, we will see another nerve coming out, also from the L234. This is the operator nerve, L234 anterior division. This runs on the medial side of the SOAS major and it goes into the pelvis and it goes through the operator canal which is a small opening in the operator membrane and it comes to the medial thigh and I shall show you the continuation of this operator nerve. So if you keep looking, I am lifting up the operator nerve here and now we will shift our focus to the medial side of the thigh and I am going to exert traction here and if you look carefully, you see this nerve here. If you watch carefully, this is the operator nerve. The operator nerve goes through the operator canal and it emerges on the thigh between the adductor magnus and the adductor brevis. And it supplies the muscles on the medial aspect, that is the adductor compartment. And it also supplies a little bit of the skin on the middle medial portion of the thigh. So that is the operator nerve. That is also L234 anterior division. And finally, we can see yet one more big nerve going into the pelvis and that is this one which I have lifted up here. This is the lumbosacral trunk, L45. This lumbosacral trunk does not come out. Instead it goes into the pelvis and it unites with the S123 and it participates in the formation of the sciatic nerve which exits the greater sciatic forearm and has the sciatic nerve. So therefore, to summarize, we have seven nerves. Some books do not consider L1 as part of lumbar plexus but then some books do. So we have already mentioned the sub-costal. We have the ilio-ing-1-L in the ilio-hypogastric that is L1. Then we have the genitofemoral, the lateral femoral cutaneous nerve, the femoral nerve, femoral nerve, obturated nerve, lumbosacral trunk. So these are all the branches that we can see from the lumbar plexus which arises from under the suase major muscles. Some of them continue to the thigh and some of them supply the muscles of the lower abdomen. Just to mention another important clinical correlation, this is the left kidney. We have lifted up the left kidney to show the posterior abdominal wall. And we can see that these three nerves, the sub-costal, the ilio-hypogastric and the ilio-ing-1-L, they form a very close posterior relation of the kidney. The same thing applies to the right side. This has got an important clinical correlation. When we are doing any surgery on the kidney and as you can see this kidney is highly honey-combed and it's a very atrophied kidney. We usually do a posterior approach, that is we approach the kidney for any purposes from the posterior aspect, even for nephrectomy. The posterior relations are the transverse abdominis, quadratus lumborum and the suase major and of course the diaphragm. Using the kidney we have to safeguard these three nerves. Sub-costal nerve, ilio-hypogastric and ilio-ing-1-L, because injury to one or more of these nerves is likely to produce weakness of the muscles of the lower abdomen and can also lead to a post-operative hernia and also it can lead to sensory loss. So these are the three nerves which have to be safeguarded. So this is the full distribution of the lumbocytrial plexus that I wanted to show you. Thank you very much for watching. If you have any questions or comments, please put them in the comment section below. Have a nice day.