the medulla oblongata is the most inferior or spinal-cord direction of the three different
pieces of the brainstem it's continuous with the spinal cord and it has a couple of surface
features that are easily recognizable here it is in a cross section of the brain and here it is on
the rubber brain stem model the most prominent aspect of the medulla are the pyramids and
that's this kind of lump that you can see here that there's a divide down the middle and then
you can see the other side of it here and here and we talked about the pyramids when we talked
about the motor system and how the motor fibers as they're traveling through the medulla come
down toward that ventral surface and form these pyramids and you can actually see them from the
surface another prominent feature is the Olivary nucleus or Olivary eminence that you can see here
on the edge and just to the medial aspect of the olive is the roots of the hypoglossal nerve and
we'll talk about that later when we talk about individual cranial nerves and here's what these
things look like on an actual brain and you can see them very clearly here's that midline kind of
sulcus here are the pyramids in between it and I suppose if you really use your imagination you can
see all those motor fibers and crossing coursing right through here and then here on the side is
our Olivary eminence so early neuroanatomists must have been hungry because they named a lot
of things in the brain for food two other important landmarks that you can see within
the medulla you have to make a cross-section of the medulla to actually see one of them is the
motor decussation and the other is the sensory decussation decussation simply means crossing
so this is where two groups of fibers are going to cross the midline we talked about the motor
decussation when we talked about motor systems remember how motor fibers come all
the way from that prefrontal cortex through the internal capsule down through the crus
cerebri through the base of the medulla as the pyramids and we've seen those on the outside of
the medulla they're going to cross the midline at the end of the medulla to become the ventral
and lateral corticospinal tracts and that's what's happening in this image the pyramids are crossing
the midline and once they've crossed then we're in the spinal cord and then we are either the
lateral or the ventral corticospinal tract remember which goes down and synapses in the
ventral horn the sensory decussation we talked about when we talked about sensory systems in
general and remember that it is the dorsal column system fine touch and proprioception that comes
in from the DRG on one side travels all the way up in the dorsal columns and here is that big
beautiful fasciculus fasciculus cuneatus nucleus cuneatus and here is the nucleus gracilis and we
talked about the fact that these fibers decussate ie they cross the midline and that's what you can
see in all of these crossing fibers here which we called the arcuate fibers so these will then
continue all the way up the up the neuraxis into the thalamus via the structure called the
medial lemniscus there are four cranial nerves associated with the medulla oblongata these are
two ventral views of the medulla and the four cranial nerves are starting bottom to top the
hypoglossal whose nerve roots are going to come out along here remember on that rubber brain stem
they're right here 9 and 10 are traveling here and those are the vagus nerve and the glossopharyngeal
nerve and then our spinal accessory poor spinal accessory kind of an outlier when you're talking
about cranial nerves most of its cell bodies are actually in the upper cervical spinal cord
they come up and through the foramen magnum and join cranial nerves 9 and 10 and then go
out through the jugular foramen to distribute to their targets I would talk a lot more about
the spinal accessory nerve when I talk about it all by itself as we go through all of the
rest of the cranial nerves in the next segment we'll talk more specifically about the pons