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 laryngopherics 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 laryngopherics 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 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 um that are going to be able to
control the size of the lumen uh 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 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
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 azygos vein and the thoracic part of the descending aorta and it's this relationship here
that allows for trans-esophageal echocardiography and also
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 motor 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 rami communicantes
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 motor
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