okay so this set util to introduce you
to the digestive system so the digestive
system is essentially a long tube which
is about six meters long and it runs all
the way from the mouth right down to the
anus so you can see how this tube is
folded in this AB abdominal area so this
increases the surface area for
absorption of nutrients so as well as
this long tube which is referred to as
the gastrointestinal tract or the
alimentary tract you've also got
accessory organs of digestion so you can
see these other organs coming off the
side of the track so this large one here
is the liver you've got the you've got
the pancreas sitting behind the stomach
and you've also got the gallbladder
sitting behind the liver so the
digestive system consists of this long
tube running from the mouth to the anus
and that includes the stomach and then
you've got the three accessory organs of
digestion so the liver the gallbladder
and the pancreas which sits behind the
stomach
so the purpose of digestion is to absorb
nutrients from the body sorry from food
and into the body and digestion involves
breaking down the food so that it can be
easily absorbed you've got sort of two
types of digestion you've got mechanical
and chemical digestion so examples of
mechanical digestion are chewing and
you've got the stomach which can
contract and churn so it can churn up
the nutrients there are the contents of
the stomach and then you've got chemical
digestion which involves enzymes
produced by various organs and glands
and you've also got acid in the stomach
and bile in the gallbladder which help
to chemically digest the nutrients from
the food so we'll just take a look at
we'll start at the start Proxima we'll
start of the mouth and work our way down
and we'll take a look at some parts of
the digestive system so digestion begins
at the mouth and the mouth is formed by
the hard palate and soft palate at the
top and you've got the lips at the front
which you can see here the sidewalls of
the mouth are made up by a muscle called
the buck Sunita muscle so if I just
isolate that you can see this muscle
called the Bucks inator making up the
sidewalls of the mouth and then you've
got the teeth and tongue inside the
mouth so you can see on this model the
upper teeth sit in the maxilla so this
is this bone of the skull and the lower
teeth sit in the mandible
so the function of the mouth is to
provide an opening for the food to enter
the body and it can it's used for
mechanically digesting the food by
chewing so if you take a look at my
turtle and muscles of mastication you
can see how the muscles can bring about
chewing movements and it also begins
chemical digestion so
you've got saliva glands which produced
saliva obviously and the saliva consists
mainly of water but there's also some
enzymes for digestion so you've got
things like saliva amylase which breaks
down starches into sugar and you've also
got lingual lipase and other and
antimicrobial enzymes
so you've got three major glands it's
library glands you've got the parotid
submandibular and sublingual glands so
if I just rotate this skull model around
I'll show you the location of these
glands so the parotid gland sits kind of
like this over here and then you've got
the submandibular gland that lies
underneath the mandible in this kind of
location and you've got the sublingual
gland which lies under the tongue and
approximately this location so you've
got three three main pairs of saliva
glands to remember so after food has
entered the mouth it passes into the
pharynx
so the funks is this sort of muscular
tube which joins onto the nasal cavity
in the the mouth and it connects them to
the esophagus and the larynx the lungs
is these these structures anteriorly
which are commonly referred to as the
voice box and behind you've got this
tube which runs down at the stomach and
this is the esophagus so I've just got
rid of the track here and you can see
the legs and you can see the track here
anteriorly which goes into the lungs and
the esophagus which runs behind it
posteriorly so the pharynx is this bit
which I'm outlining here between the
nasal cavities the back of the old
cavity and just sitting above the track
here and the esophagus so there are
three parts to the funks you've got the
nasopharynx
the oropharynx and the lemon go pharynx
so food passes out of the old cavity
into the oropharynx and then you've got
various muscles constrictor muscles
which contract and propel the bolus of
food from the oral cavity through the IO
pharynx and into the lungs effects and
then it passes down into the esophagus
below so during swallowing the soft
palate actually swings up and closes off
the nasopharynx