hi let's talk about the liver
in this video we'll discuss the basic structure and features of the liver and gallbladder
the liver is a large intraperitoneal organ that is found in the right hypogastric
and epigastric regions of the abdominal pelvic area it's an accessory organ of digestion meaning
it's not a part of the digestive tract or gut tube but it does secrete substances into that gut tube
it performs a variety of functions in this vein and in others it produces and secretes
bile for the emulsification of fats it helps to regulate concentrations of blood glucose
it helps to convert ammonia into urea it serves as a place to store iron for hemoglobin
it's also part of several processes for helping to filter the blood and it produces
cholesterol and proteins and has a variety of other functions as well
the liver can be looked at in terms of its constituent parts either anatomically or
physiologically anatomically there are four lobes to the liver there is a dominating right low and
also a rather large left lobe looking at the visceral surface here so this would be posterior
this would be anterior this would be right and left we can see the very large right lobe there
and left lobe there there's also a caudate lobe and it's obscured here by the gallbladder but
a quadrature lobe as well the quadrate lobe is anterior the caudate lobe is posterior more
often than not these caudate and quadrate lobes are grouped anatomically with the
right lobe when we discuss function in terms of anatomical lobes when we look at the liver
physiologically or purely from a functional perspective there are eight different segments
that don't fall neatly into these anatomical lobes and each of these segments are served by
independent branches of the hepatic portal vein the hepatic artery proper and these two vessels
are going to be what sends blood into the liver sinusoids and
each segment is also going to have its own branch of the bile duct and so bile is going to
leave the liver and enter into the the biliary tree from each of these eight segments
there are five surfaces of the liver there is a superior surface which we
can see here that superior surface is in direct contact with the diaphragm
opposite the superior surface there is the inferior surface most commonly referred to as the
visceral surface because it's facing the abdominal viscera and then there is a right surface that
right surface is facing right laterally and a posterior surface of the liver which is facing
posteriorly towards the diaphragm there are several peritoneal ligaments that are going
to anchor the liver in place most substantially superiorly here we have the coronary ligament
the coronary ligament is going to blend into the falsiform ligament which is going to anchor
the liver to the diaphragm we can't see it but posteriorly there are elements of the coronary
ligament as well and at the edges those elements of the coronary ligament blend with the
triangular ligaments so there are left and right triangular ligaments between these spaces there is
no peritoneum in contact with the liver and that's what we would refer to as the bear
of the liver that's more on the posterior surface of the liver that falsiform
ligament is going to be riding along the superior edge of the round ligament of the liver
so the falsiform and round ligaments of the liver are going to be very closely associated
with one another the round ligament of the liver or ligamentum teres hepatis is not to be confused
with the round ligament of the uterus and then we also have elements of the lesser momentum
which are associated with the visceral surface of the liver so there is the hepatogastric ligament
which attaches the liver to the stomach and the hepatoduodenal ligament which is going to
attach the liver at the porta hepatis which we'll discuss on the visceral surface to the duodenum
so the visceral surface is going to have a lot going on most substantially
there is this area called the porta hepatis so the porta hepatis is going to conduct
several major vessels in and out of the liver so i guess we can begin with the elements
that are within that hepatoduodenal ligament that are also part of the portal triad so we have the
hepatic portal vein and its tributaries we also have the hepatic artery proper and its right and
left branches so those two vessels are delivering blood into the liver sinusoids
there's also the bile duct or the uh common hepatic duct and its branches there
so these are entering and exiting at the porta hepatis also along for the ride will
be elements of the hepatic nerve plexus this is an autonomic plexus that is riding in the branches of
the hepatic artery proper and like most things along for the ride we have lymphatics as well
so we can see a few other elements here on this visceral surface let's just point out this is
posterior and this is anterior we can also see the gallbladder is associated with the
visceral surface here often times it will be intraperitoneal but it also may be intrahepatic
so in lab if you're looking for the gallbladder and you know that your donor has one meaning it
hasn't been removed you may actually have to look within the the substance or the parenchymum of
the liver to find it we can also see and this is more an element of the posterior surface
there's going to be a groove for the vena cava which is going to hold the inferior vena cava
there's also going to be a groove for the round ligament
and within that will be the round ligament of the liver that round ligament of the liver is
a remnant of the fetal umbilical vein so this umbilical vein is going to conduct blood from
the placenta up to the the fetus going towards the heart so it will enter into the hepatic
sinusoids there there is also a bypass for those sinusoids called the ductus venosus in the fetus
it is obliterated in the adult and it's called the ligamentum venosum which can be found
in the uh in the groove for the ligamentum venosum on that visceral surface as well
and these are things to uh to keep a look at for when you're examining the visceral
surface of the liver we can also see i mean just to remind us there is the right lobe and the left
lobe and the caudate lobe and the quadrate lobe all visible on the visceral surface
it's useful to think about the relative physiological relationships of these anatomical
structures when we think about the liver and so there are four things going on here that i really
want to bring together in one slide so when we think of blood supply to the liver there are
two sources uh the hepatic artery proper which we can see here being conducted up through what
would be the hepatoduodenal ligament so that's going to be a branch of the common hepatic
artery from the celiac trunk and then there's also the hepatic portal vein also going to be
transmitted up through that hepato hepatoduodenal ligament the hepatic portal vein is going to
conduct blood from the capillary beds of the gastrointestinal tract
up into the liver sinusoids so portal vein portal venous vein
i'm sorry portal venous blood is going to mix with blood from the hepatic artery proper
into the liver sinusoids the sinusoids are then going to be drained through a series of hepatic
veins which are part of the caval system the caval system includes all of the veins that drain into
the superior or inferior vena cava which are conducting that blood back up to the
right atrium of the heart and typically there are three of these hepatic veins
separate from all of this are going to be bile canaliculi so tiny little
bile canals which will coalesce into ducts which are going to be the proximate portions of the
biliary tree or the biliary tract depending on preference of those who are communicating it and
that biliary tract is going to conduct bile from the liver to and from the gallbladder down to the
major duodenal papilla it coalesces with the main pancreatic duct into the
the hepatopancreatic ampulla which then is going to secrete through the major
duodenal papilla into the second part of the duodenum this papilla and these secretions
represent the division between the foregut and the midgut
so while we're talking about the biliary tree or the biliary tract we should uh we should tip our
hats to the gallbladder the gallbladder is an intraperitoneal organ although it can be found
within the substance of the gallbladder so it may be intra-hepatic it serves as a storage sac for
bile and it's typically going to appear as green it uh green because bile is more often than not
green it contains two pigments uh bilirubin in biliverdin biliverdin is the oxidated form of
bilirubin and that is going to impart a green hue to anything that contains it so the biliary tract
may be more green than not and sometimes even the the parenchyma of the liver that surrounds the
gallbladder maybe stained green as well so we can see the the gallbladder is drained
and filled through the cystic duct that cystic duct joins with the common hepatic duct
and where the two combine we have the common bile duct sometimes just called the bile duct
that gallbladder is supplied with blood from the cystic artery
now with respect to the autonomic innervation of the liver and gallbladder the plexus responsible
for this is the hepatic plexus and the hepatic plexus is going to be conducted
up to the visceral surface of the liver largely along the branches of the hepatic artery proper
it's going to originate from two sources the celiac plexus which we can see here that celiac
plexus is a mixed autonomic plexus which is going to incorporate fibers from the posterior vagal
trunk as well as the thoracic splanchnic nerves the splanchnic nerve's synapse in the celiac
ganglia the posterior vagal trunk fibers just pass through them and these are going to move
along the celiac trunk along the common hepatic artery out through the hepatic artery proper
up to the liver there will also be branches from the anterior vagal trunk and we can see there's
the anterior vagal trunk there and that anterior vagal trunk sends branches to the stomach but also
over to the liver and gallbladder and there may even be some branches from the superior mesenteric
plexus as well referred pain from the liver is going to present to either the epigastric region
or the right hypochondriac region so it'll be felt towards the
right lateral or central superior portion of the abdomen so we've discussed the structural
and functional divisions of the liver as well as features of the various surfaces of the liver in
particular the visceral surface of the liver and in particular the porta hepatis we've talked about
the the various functional and anatomical relationships of these
features as well as the innervation this is your summary slide thank you for your time