hi let's talk about the aerodigestive pathway with this just of portion of this pathway so
the aerodigestive pathway consists of all of the structures that are common between
the respiratory and the digestive systems so these would include the mouth the oral or buccal
cavity and the pharynx or the colloquially throat and in particular because we're focusing on the
digestive portions of the arrow digestive pathway we're going to look at the oral pharynx and the
laryngopharynx the mouth or the oral opening is the space between the lips now the space is
controlled by a muscle called the orbicularis Oris and it can be further modified by other muscles of
facial expression now it's important to realize is that all of these muscles are under control of
cranial nerve seven or the facial nerve in order for you to move the mandible or to participate
in a process known as mastication we need to bring in innervation from another nerve which
would be the mandibular nerve commonly known as v3 which is the third portion of the trigeminal nerve
or cranial nerve number five beyond the mouth is the oral cavity in the oral cavity has two
major spaces first there's the oral vestibule the oral vestibule is the space that is outside of the
teeth and the gingiva so this space is a rather minor portion of the total oral cavity but it is
important because ingested fluids and materials do make their way here and there's also secretion
from one of the major salivary glands called the parotid gland into the oral vestibule so
the openings of the parotid ducts are located there just adjacent to the maxillary second
beyond the oral vestibule we have the teeth which are important for physical digestion
that are supported by the bones of the maxilla and the mandible and surrounded at their roots
by your gums or your gingiva beyond the plane of the teeth and the gingiva is the oral cavity
proper and that oral cavity proper is going to contain the tongue as well as the openings for the
submandibular gland ducts and the sublingual gland ducts which are going to open at the floor of
the oral cavity proper the oral cavity proper is going to extend posteriorly to the palatoglossal
arch that palatoglossal arch is the division between the oral cavity and the oral pharynx
now teeth are important structures for physical digestion they in size they tear and they grind
materials brought into the oral cavity now you can conceptualize teeth as existing in four quadrants
so your maxilla is going to host two quadrants of teeth and the mandible is also going to host two
quadrants of teeth there are two types of teeth there are deciduous or milk teeth deciduous teeth
are those that erupt after birth and then begin falling out of the gingiva at approximately five
years of age and beyond in terms of the deciduous teeth there are twenty total and in each quadrant
an individual is going to typically have two incisors one canine and two molars so five per
quadrant four quadrants for 20 total in terms of your adult teeth these are the teeth that typically
replace the deciduous teeth individuals will typically have thirty-two teeth in each quadrant
this course bonds to two incisors and we can see the incisors here there's a central incisor and
then a lateral incisor the incisors are flanked by the canines and there is one per quadrant and then
looking at this laterally canines are then flanked by two premolars typically and then there are
three molars many individuals may have variation with respect to the molars they may only have two
some individuals may opt to have their third molar oftentimes referred to as the wisdom tooth removed
to prevent any issues of crowding also within the oral cavity proper and the pharynx is the tongue
the tongue is a muscular structure that is highly kinetic or mobile within the oral cavity and the
pharynx it helps us to move food materials it also helps us to experience the sensation of gustation
or taste compliments of gustatory receptors that may be distributed upon papillae of the time these
papillae may take the form of fungiform papillae which are larger mushroom-like eruptions the
fungiform papillae are responsible for hosting the lion share of gustatory receptors more ubiquitous
than the fungiform papillae are smaller filiform papillae distributed throughout the tongue or
tastebuds filiform papillae i typically do not host gustatory receptors and oftentimes people
may mistakenly refer to the papillae themselves as taste buds there are also folate papillae on the
sides of the tongue these may host gustatory receptors but they typically only do so in
childhood and then they diminish as a person ages and then there are also valley papillae sometimes
refer to as circumvallate papillae towards the the posterior portion of the body of the tongue
now with respect to the tongue there are two major portions there's the body of the tongue
the body of the tongue is the portion that you most typically will see this extends back to
the terminal sulcus and then there's the root of the tongue or the pharyngeal partion of the
tongue that exists beyond the poetic lhasa arches so those plateau colossal arches are the division
between the oral cavity and the oral pharynx so the body of the tongue exists in the oral cavity
whereas the root of the tongue exists in the oral pharynx now with respect to the innervation of the
tongue there are a couple of different innervation components so there would be the somatic muscular
control of the tongue this is controlled by the hypoglossal nerve cranial nerve 12
there's also going to be somatic afferent or the sensory portion that which you can
feel from the tongue for most of the tongue so up to the valley papillae this is going
to be modulated by the lingual nerve which is a part of v3 in areas posterior to that
that row of valate papillae it's going to be the glossopharyngeal nerve which is cranial
nerve nine now in terms of special senses in particular taste we're going to see a very
similar pattern of innervation the majority of the body of the tongue is actually going
to be innervated by chorda tympani which is of the facial nerve cranial nerve seven by way of
the lingual nerve so those fibers are going to hitchhike on the lingual nerve whereas the
valley papillae and posterior are going to be innervated for taste via the glossopharyngeal
nerve there are large aggregations of lymphatic material along the root of the tongue this is
referred to collectively as the lingual tonsils and it's restricted to the pharyngeal portion
beyond the oral cavity so in regions beyond the palatoglossal arch we have the pharynx as you
may recall the pharynx consists of a nasal pharynx and oral pharynx and the laryngopharynx the oral
pharynx is going to be the space between the soft palate and down to the line of the epiglottis so
this is going to be contiguous space of the pharynx in the oral cavity so food materials
are going to pass into the oral pharynx and then they'll move into the laryngopharynx and it's at
this point of the arrow digestive pathway that materials may either move anteriorly into the
lyrics and then the trachea beyond which would be the respiratory system or posterior lis into the
esophagus the transition from the laryngopharynx into the esophagus begins at the inferior border
of the cricoid cartilage so that's approximately at the level of c6 so we've discussed the areas
from the mouth through to the opening of the esophagus let's now move on and take a look at the
esophagus or that fibromuscular pathway that leads between the pharynx and the stomach thank you