 Good day everybody. Dr. Sanjay Sanyal, Professor Department chair. So this is going to be a demonstration of the lumbar plexus originating from the lumbar region abdomen first 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 to speed We have completely opened up the thorax in the abdomen and this is the first abdominal wall This muscle that we see here This is the so-as 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 so-as which is going to the thigh So these are the muscles of the posterior abdominal wall. Now, let's take a look at the nerves which are emerging from the lumbar plexus We can feel the twelfth 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 twelfth rib is this one This is the subcostal nerve T12 this supplies the lower abdominal muscle and After that it also supplies a skin the next now 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 ilio hypo gastric and the ilio inguinal. The ilio hypo gastric 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 ilio inguinal 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 ilio inguinal goes through the inguinal canal this ilio inguinal 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'm 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 of 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 superior spine 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 antrolateral 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 parasthesia on the antrolateral aspect of the thigh And that condition is referred to as Meralgia parasthetica. 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 suas major muscle and we can see it is going here This is the genitofemoral L12. It's got two components, a genital 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 ligament It goes through the spheromatic cord and it supplies the cremaster muscle and it also supplies the antrolateral 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 suas major And I will go under the suas major and I am going to reflect the suas major and we can see the other portion of the nerve here This is L234 posterior division, the femoral nerve And I'm 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'm 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's 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'm lifting up the operator nerve here and now we will shift our focus to the medial side of the thigh And I'm going to exert traction here, and if you look carefully You see this nerve here Watch carefully This is the operator nerve Operator nerve goes to the operator canal and it emerges on the thigh between the adductor Magnus and the revis And it supplies the muscles on the medial aspect That is the adapter 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 foreman 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-postal 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 Operator nerve Lumbosacral trunk So these are all the branches that we can see from the lumbar plexus Which arises from under the swast major muscle 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-postal 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 is what an important clinical correlation when we are doing any surgery on the kidney And as you can see this kidney is highly honeycomb 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 transfer sub-dominus quadratus lumborum and the swast major and of course the diaphragm while we are reaching the kidney We have to safeguard these three nerves sub-costal nerve ilio-hypogastric and ilio-ing-1-L because injury to a one or more of these nerves is likely to produce weakness of the muscles 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 lumbosacral plexus that I wanted to show you Thank you very much for watching. Dr. Sanjay Sanyal signing out if you have any questions or comments Please put them in the comment section below. Please like and subscribe