Are you searching for Lumbar plexus mnemonic to remember the abdominal and lower limb nerves?
The Lumbar plexus is a network of nerves arriving from the lumbar vertebrae.
But do you want easy ways to keep its anatomy in your memory even in the long term? Then you’re in the right spot!
In our previous Snacky medmonics, we discussed the Glycogen storage diseases and their mnemonics.
In today’s post, we’d be dwelling on the anatomy of the Lumbar plexus as well as easy mnemonic you can use to keep everything in memory!
Let’s jump in right away!
What is the Lumbar Plexus?
There are 5 supporting vertebrae in the body.
Absolutely yes, there’s the Cervical, thoracic, sacral, coccyx and now, the Lumbar vertebrae!
Now, The network of nerves which arises from the anterior rami of the spinal nerves, is known as the lumbar plexus.
From its origin in the abdomen, it courses down to the lower limb where its branches supply major muscles and structures.
However, note that the lumbar plexus arises from L1 to L4. That is the spinal nerves from the first to the fourth lumbar vertebrae.
The fifth one (L5) contributes to what is known as the Lumbosacral plexus after joining with nerves from the sacral plexus.
What are the Network of Nerves in the Lumbar plexus
Like we said earlier, the lumbar plexus is a network of anterior branches of the spinal nerves of the lumbar vertebrae. There are six major branches of nerves that make up the lumbar plexus:
- Iliohypogastric nerve
- Ilioinguinal nerve
- Genitofemoral nerve
- Lateral cutaneous nerve of the thigh
- Femoral nerve
- Obturator nerve
Now let’s get into details in the Lumbar plexus mnemonic!
1. Iliohypogastric nerves
Let’s decode the complex word, shall we? Iliohypogastric is coined from “ilio” and “hypogastric”.
If you can remember, the Innominate hip bone consists of three parts- ilium, ischium and pubis. Then hypogastric is the lower part of the abdomen after being divided into regions.
So this nerve is the first from the lumbar plexus and it courses around the ilium.
It’s nerve root is L1 but it receives a branch from the T12. Hence it;s root becomes T12, L1.
It gives both sensory and motor supply to the muscles of the abdomen, that is the External, Internal Oblique and transversus abdominis.
2. Ilioinguinal nerve: Lumbar Plexus Mnemonic
The next nerve on the lumbar plexus before we talk about mnemonic is the Ilioinguinal nerve.
It begins superiorly from the first lumbar vertebrae, and goes all the way down in the abdomen between the internal oblique and transversus abdominis.
It finally passes through the Inguinal canal where it exits from the superficial inguinal ring.
Nerve root: L1
It supplies the internal oblique and transversus abdominis. It also pierces the external spermatic fascia of the cord to supply the skin of the root of the penis and also anterior part of the scrotum.
Finally, it ends as a terminal cutaneous branch that supplies the skin of the medial portion of the thigh around the inguinal ligament.
3. Genitofemoral nerve
The third nerve on the lumbar plexus is the Genitofemoral nerve having nerve root L1, L2.
Watch how the root’s increasing in value? Nice, we’d use this in coding the Lumbosacral plexus mnemonics.
Now there’s something to note; it has two branches- the genital and femoral branch.
The femoral branch is cutaneous, pierces the femoral sheath and the deep fascia to supply the skin over the femoral triangle.
The genital branch goes through the deep inguinal ring following the other structures in the spermatic cord. It supplies the Labia majora.
5. Lateral Cutaneous Nerve of Thigh
The Nerve root is L2,3, and it’s the major cutaneous innervation to the lateral side of the thigh.
5. Femoral nerve- Lumbar Plexus Mnemonic
The next on the Lumbosacral plexus mnemonic is the femoral nerve. It originated as the posterior division of the anterior branch of the L2,3,4.
It is regarded as the main nerve of the extensor/anterior compartment of the thigh. It supplies the Rectus femoris, Vastus medialis, intermedius, lateralis and Sartorius.
It starts by passing in the iliac fossa between the Iliacus and Psoas muscle supplying the muscles before it enters through the inguinal ligament and lateral to the femoral sheath.
Note: the femoral sheath contains the femoral artery and vein. The femoral nerve is not a content but lies lateral to it. You can use the mnemonic NAVEL to remember the position where;
- N- Nerve
- A- Artery
- E-empty space
- and L-lymphatics.
In the femoral triangle, the femoral nerve supplies the Pectineus and immediately below the inguinal ligament; it gives off cutaneous branches— the Intermediate and medial cutaneous nerve of the thigh. What do they supply?
They’re part of the cutaneous branches you’d find after dissecting the skin and superficial fascia, lying on the anterior thigh.
The intermediate pierces the Sartorius and the fascia late to move anteriorly supplying the middle front of thigh down to the knee joint. In the same vein, the medial cutaneous nerve goes medically, also piercing the fascia lata to give nervous sensations to the medial aspect of the thigh.
Also note: the femoral nerve is from the posterior division of the anterior branch of the L2,3,4 while the obturator nerve is the anterior discussion of the same rami. You can use a quick mnemonic like FP to denote that femoral nerve is to posterior division.
6. Obturator nerve
The obturator nerve is the major nervous supply to the muscles in the medial compartment of the thigh. Its nerve root like we described earlier is L2,3,4.
However, it has two divisions- the anterior and posterior which later goes on their separate course to give branches to different muscles in the medial compartment.
The Anterior compartment supplies the Adductor brevis, Longus, And Gracilis, and ends in the subsartorial plexus which further gives innervation to the skin of the medial side of the thigh.
The posterior compartment supplies the Obturator externus, Adductor magnus and gives a terminal branch that follows the femoral artery through the hiatus.
So the mnemonic you can use to remember the Lumbosacral plexus is:
- I– Iliohypogastric: T12, L1
- Insist– Ilioinguinal: L1
- Go– Genitofemoral nerve: L1, L2
- Learn– Lateral cutaneous nerve of thigh: L2, L3
- Femoral– Femoral nerve; L2, L3, L4
- Operation– Obturator nerve: L2, L3, L4.
Also Read: 5+ Brachial Plexus Mnemonics For Easy Recall
How to remember the Lumbar Plexus Mnemonic
Now let’s move over to the coding system for remembering the nerve roots!
- All the Nerve roots increase in addition to the former except the Femoral and Obturator nerve.
- Each nerve has two roots except Ilioinguinal, Femoral and Obturator.
Do you know what I mean? Here’s it;
The Iliohypogastric nerve has roots from T12 and L1. Then the Ilioinguinal arrives from L1. So the next is going to be L1 plus L2, which is the Genitofemoral nerve. You get the gist?
Now what’s going to be the root for the Lateral cutaneous nerve of the thigh? L2, L3! That’s right, you get it!
So, that of femoral and Obturator will together be L2,3,4. But note! These two nerves arrive from the same rami but different divisions.
The Obturator nerve is from the anterior division of the anterior rami of L2,3,4 while Femoral is from the posterior.
The mnemonic I use to remember their arrangement is FP. Which means Femoral is to posterior. And from that you should know the opposite is Obturator to Anterior!
Also Read This Post On How to Study Anatomy Excellently in Med School
So there you go; Lumbar Plexus mnemonic for easy recall!