hi let's talk about the esophagus in this video we'll discuss the parts of the esophagus the
pathway of the esophagus from the neck through to the abdomen and how the esophagus is innervated
the esophagus is a muscular tube that spans the distance between the pharynx and the stomach
it's approximately 25 centimeters long and if we were to divide it into thirds the proximal third
would be striated muscle which is innervated by the recurrent laryngeal nerves and
served by the inferior thyroid arteries and the distal two-thirds
would consist of smooth muscle under the control of the esophageal autonomic plexus and supplied
by blood by bronchial and esophageal arteries the first part of the esophagus is the cervical part
not pictured here it runs from the laryngopharyx which is transitioning into the esophagus
at the opening of the esophagus at approximately the level of the cricoid cartilage c6
which then at the root of the neck transitions into the thoracic
part of the esophagus which we can begin to to see here that thoracic part of
the esophagus is then going to move through the posterior mediastinum
conveyed through the esophageal hiatus of the diaphragm
which is approximately at the level of t10 where it becomes the abdominal part of the esophagus
which terminates in the cardiac region of the stomach
so that cervical esophagus which we can see here is going to be contiguous with the laryngopharynx
so what i've just outlined is the inferior pharyngeal constrictor muscle that inferior
pharyngeal constrictor muscle has two parts this part is the thyropharyngeal part and below that
is the crico pharyngeal part both of these parts originate in some portion of the larynx either the
thyroid or cricoid cartilage and then meet their counterpart along the midline pharyngeal rough a
both of these parts are part of the upper esophageal sphincter and the cricopharyngeal part
is the most significant component of that upper esophageal sphincter the esophagus has
two sphincters that are going to be able to control the size of the lumen
and this upper esophageal sphincter it's important to note is within the
pharynx not within the esophagus so this precedes the esophagus nevertheless
this portion of the esophagus the cervical part is comprised of striated muscle
innervated by the recurrent laryngeal nerves and supplied by blood via the inferior thyroid
arteries those are branches of the thyrocervical trunk of the first part of the subclavian artery
it's along these inferior thyroid arteries that will have branches from the
cervical sympathetic ganglia sending out fibers along through perivascular plexuses of these
inferior thyroid arteries so these will be vasomotor fibers to control the uh the vasculature
at the root of the neck the cervical esophagus transitions into the thoracic esophagus
and in the superior mediastinum this will continue its association with the trachea with
being behind or posterior to the trachea as the trachea divides into the primary bronchi
um the esophagus will continue inferiorly we're now at the level of the posterior mediastinum and
we'll see that uh the esophagus has a very close relationship with the posterior aspect of the
pericardium and therefore the heart and it will be an intermediate between the azages vein and the
thoracic part of the descending aorta and it's this relationship here that allows
for trans-esophageal echocardiography and also um imaging of the thoracic aorta from within
the esophagus um as we move into this region of the posterior mediastinum the esophagus is now
smooth muscle and that smooth muscle is going to be under autonomic control and the plexus which
controls that smooth muscle is the esophageal plexus which we'll talk about in greater detail
the esophagus is then going to be conveyed through the esophageal hiatus of the diaphragm
at approximately the t10 level and we'll pick up as the abdominal part of the esophagus but first
let's discuss this esophageal plexus there are inputs both parasympathetic and sympathetic to
this autonomic plexus the parasympathetics are going to be the dominant fiber within the plexus
as the vagus nerves here we see the left vagus nerve become the vagal trunks so we'll have an
anterior and a posterior vagal trunk the anterior is predominantly comprised of left vagus fibers
with some right the posterior is predominantly comprised of right vagus fibers with some left and
the greatest effect that the parasympathetics will have on the esophagus is that of peristalsis or
wave like rhythmic contractions of the esophagus so as to encourage the distal propulsion of food
materials down toward the stomach any associated visceral aphid fibers with these parasympathetic
fibers are going to be feedback to the autonomic nervous system or reflex involved the sympathetic
fibers are going to originate from preganglionic fibers so these will be white raymi communicates
at the level of ventral primary rami of thoracic nerves t4 through t6 typically the superior two
ganglia so four and five are going to send fibers up to the cervical sympathetic ganglia and those
will be involved in the perivascular plexuses that route out along the inferior thyroid arteries
the postganglionic fibers will come from a variety of sources so there will be some
branches from the middle and inferior cervical ganglia but most of those fibers will stay
local and remain as vasomotor fibers of the perivascular plexuses along the
inferior thyroid arteries some may descend down towards the cardiac plexus and beyond as
we know that there is significant communications between cardiac pulmonary and esophageal plexuses
and then there will be direct branches from t4 to t6 ganglia out to the esophageal plexus as there
will be communications of cardiac branches from superficial and deep cardiac plexuses as well
in terms of the response the effects of sympathetic innervation will be vasoconstriction
much like nearly all other sympathetic effects on vasculature any associated
visceral affirmative fibers with sympathetic fibers will conduct visceral pain fibers back
visceral pain is very difficult to localize and it's felt differently than somatic pain
and since these are being conducted along t4 to t6 and these are also serving the cardiac plexuses
any esophageal pain might be felt as burning or dull pain around the heart hence the the term
heartburn when associated with esophageal injury from acid reflux from the stomach
then finally the most distal part of the esophagus is the abdominal part which is conducted
through the esophageal hiatus we can see that esophageal hiatus here and we can also see the
anterior vagal trunk located here as well as the posterior vagal trunk located there that abdominal
esophagus is going to deviate to the left and it's going to empty into the cardiac region
of the stomach and it's therefore going to sometimes be referred to as the cardiac
sphincter or the gastroesophageal sphincter this is the lower esophageal sphincter
this is supplied by branches from the left inferior phrenic artery
not seen here as well as the left gastric artery which is a branch of the celiac trunk which we'll
discuss in much greater detail in the gi sessions so we've discussed the parts of the esophagus
the different types of muscle which comprise the wall of the esophagus
the blood supply to the esophagus and the innervation to the esophagus both of the somatic
recurrent laryngeal nerves as well as the esophageal plexus and the vagal and
sympathetic trunk inputs to that plexus this is your summary slide thank you for your time