Swallowing will help get that food stuff
from the mouth down to the stomach
where you can start
to mix and grind it.
Swallowing is broken up into
three different components.
One is a voluntary part and
there are two involuntary parts.
But to start swallowing
is a voluntary process.
Once you’ve pushed the food stuff
back far enough in the throat though,
you will enact an
And this can be seen in
this particular diagram
where we have the hard
palate and soft palate.
The bolus of food there can be seen
in the mid portion of the diagram.
That will be pushed a little bit backwards
as this is delivered to
the back of the throat.
You see it touches up
against the epiglottis,
which will then close
over the airway,
And that is done so that when you swallow,
it goes down the esophagus and
not the larynx and the trachea.
So the pharynx, you can think of that
at the top of the swallowing reflex.
At the bottom of the
reflex is the stomach.
There are two different
sphincters that are involved.
One is the upper esophageal sphincter
and the other is the lower
I will highlight the lower
esophagal sphincter right now
because this is a site
often of pathology.
So when people have an acid reflux or
regurgitation or Barrett’s esophagus,
these are problems that are associated
with this lower esophageal sphincter.
What’s interesting about the
whole process of swallowing
is that it’s partly voluntary
and partly involuntary.
Corresponding to that, there are striated
muscles in the upper third portion
of the swallowing
The bottom two-thirds is
composed of smooth muscle.
You don’t have the ability
to regulate or voluntarily
It is a reflex response.
There is a swallowing center
that’s located in the brainstem.
And this will coordinate both
the striated and smooth muscle
to try to get that whole
bolus of food pushed
down the esophagus in
a coordinated manner
because you can imagine if you did
not have coordinated contractions,
the bolus of food could get stuck
somewhere along the esophagus.
Besides the swallowing center,
there are a couple of
different types of regulatory
responses that will synapse to that.
One is part of the glosso pharyngeal nerve,
which will provide some feedback from the
efferents located in the throat area.
So these nerves will directly
stimulate this muscle to contract.
Then the autonomic nerves
will then be engaged
usually more of a reflex
type of a manner.
So let’s go through this process
know as primary peristalsis.
The first wave of contraction that happens
once you start the swallowing reflex,
pushes food from, again, right at the back
of throat all the way down to the stomach.
If for some reason,
that primary peristalsis did not move
all the food down to the stomach,
you have a secondary mechanism
called secondary peristalsis
that will begin the process again.
What you need to have though at the
bottom of the swallowing reflex
is you need to have
a relaxed stomach.
If the stomach was not relaxed,
it would be unable to accept the
food that would come to it.
So in this case, you have to
release tonic constriction
of the lower
And that is done via a
vasoactive intestinal peptide
and one thing called receptive relaxation
which is the top part of
the stomach also relaxing.
So you relax the lower esophageal sphincter
and the top part of the stomach,
both with vasoactive
in order to accept the food
that is coming down the throat.
Now, how do you coordinate
these waves of contraction?
This can be seen in this type of a diagram
where you have time on the X-axis and this
is where the striated and smooth muscle is.
That’s the upper
We had to put a pressure
transducer down the throat
to be able to get these
nice little waves.
And then there’s the lower
So as you can see, there is a
coordinated increase in pressure
in a different timeframe all
the way down to the stomach.
And hopefully, you can also see at
that lower esophageal sphincter,
there is a relaxation that occurs
when you’re contracting the
upper portion of the esophagus.
So here’s swallowing beginning
and there is the
relaxation of the stomach.