Introduction – Lumbosacral Plexus

00:01 In this lecture, we’re going to look at the lumbosacral plexus. So we’ll look at the lumbar plexus, the sacral plexus, and the coccygeal plexus, with all of these constituting the lumbosacral plexus. Contributions for the lumbar plexus are from T12, L1, L2, L3, and L4. Sacral plexus, we have contributions from L4 all the way down through to S4, and this is important as it gives rise to the sciatic nerve. And then, the coccygeal plexus which is coming from S4, S5, and the one coccygeal spinal cord segment. Let’s look at the lumbar plexus, first of all. This, as we can see on the screen at the moment, it gives rise to a whole series of nerves. We can see the lumbar plexus coming down here giving rise to a whole series of nerves, then it goes to supply structures in the abdominal wall and also in the thigh. So the lumbosacral plexus is part of the lumbar plexus, also the sacral plexus and the coccygeal plexus. It is analogous to the brachial plexus in the upper limb. And then it gives nerves towards the musculature of the lower limb to supply the various compartments, and it also receives essential information from the lower limb that pass back towards the spinal cord. Just like the upper limb, sympathetic fibres join the lumbosacral plexus, and this is taking sympathetic fibres towards the body wall, and this is passing to the lumbar plexus, lumbosacral plexus by way of the grey rami communicants, just the way as they did for the upper limb. So if we start by looking at the lumbosacral plexus, then we can see the lumbar plexus is formed from T12 down to L4, so T12 all the way down to L4 - spinal cord nerves leaving from these spinal cord segments from the lumbar plexus. Then the sacral plexus all the way down from L4 to S4, or sometimes, the first coccygeal, the only coccygeal segment. And then the coccygeal plexus, S4, S5, and the only coccygeal segment which we can see here. So, these three plexi together form the lumbosacral plexus. If we look at the lumbar plexus in-situ,