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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,