hi let's talk about the sacral plexus and one of its branches the pudendal nerve
so the sacral plexus is going to be derived from ventral primary rami of s1 through s4 and also
include a component of the lumbosacral trunk which has fibers from l4 and l5 now those sacral spinal
nerves are going to traverse the sacral canal here we're looking at a posterior view of the sacrum
and then they're going to exit through the anterior sacral foramina on the ventral surface
of the of the sacrum kind of like that these dorsal or posterior sacral
foramina are for the dorsal primary rami of those sacral nerves over here on the pelvis we can see
the sacrum in situ and we can see the anterior sacral foramina well at least some of them
positioned there here we can see in a hemi pelvis a left hemi pelvis and let's uh outline for us
the lumbosacral trunk coming down again the lumbosacral trunk is conducting fibers of l4
and l5 here we have the first sacral nerves vpr so that's s1 here is s2 there is
s3 and this itty-bitty
is s4 now in other contexts we've described how various branches from either the sympathetic
trunks so sacral spanchnics or branches of these ventral primary rami that are parasympathetic
i.e pelvic splanchnics are going to contribute to the inferior heavy gastric plexus but let's
keep this somatic so derived from branches of s2 3 and 4 we are going to see a pudendal nerve
that pudendal nerve is going to exit the pelvis through the greater sciatic foramen
it's going to wrap around the ischial spine and it's going to conduct itself through the
lesser sciatic foramen as it travels into the pudendal canal or Alcock's canal
now let me give you a few uh points of orientation here just so we can sort of understand it behind
these ventral primary rami i'll just kind of run over them here this is the piriformis muscle
i always misspell this with a y piriformis muscle
here is the ischiococcygious muscle or just the coccygeal muscle
and coming down here from the tenderness arc of levator ani across is going to be the ilio
coccygeus
muscle or the iliococcygeus part of levator ani and we can see right oops let's go back to
there the that proximal part of the pudendal nerve as it's
diving down sort of behind these muscles here is a view of the perineum in
lithotomy position let's let's give us a little context here so here would be
the the vestibule of the vagina with the the labia minora here is the anal canal
with the external anal sphincter here's the pudendal canal there and let's take a look at
what's coming through here so we've got the pudendal nerve and some of its branches
in fact some of these branches in particular the inferior rectal are going to branch off
in the pudendal canal to serve the external anal sphincter and then we'll have a variety of other
branches of the pudendal nerve so for instance here we have
that's the posterior labial nerve which is of the superficial perineal nerve there's
that's sensory from the perineum here's the deep perineal going under
the membrane that is going to be motor to the issue cavernosus muscle and bulbocavernosus muscle
and then rounding it out we've got the dorsal nerve of the clitoris so this is the pudendal
nerve in a nutshell and for this session you are in particular responsible for these
inferior rectal nerves sometimes called inferior anal nerves so that's the uh the sacral plexus
and the pudendal nerve in particular will go into greater detail of some of
the derivatives of the sacral plexus like the the sciatic nerve um in its components
and some of the other nerves which serve the hip in msk thank you very much for your time