Digestive System 8- Digestive accessory organs

Digestive System 8- Digestive accessory organs

January 8, 2020 4 By Ewald Bahringer


– Now, there’s two
accessory organs that we’re going to explore, and they are the liver,
which is right here, and the pancreas,
which is right there. And we already
talked about the fact that all of our digestive juices
are dumped into the duodenum, and it’s true, they both empty
into the duodenum through a structure called
the duodenal papilla. So, let’s look really
briefly at what they do. The liver, the liver, I wish we could
have a liver class, like, that would be
a phenomenal course to take, because the liver does
like a billion things. And, like, the physiology
of the liver is shocking. The anatomy of
the liver is shocking. Every bit of blood from your digestive
system travels to the liver. All the blood that’s
absorbing material, so you’re absorbing stuff
from your lumen of your digestive tube
into your blood, all of that blood goes
to your liver before it goes anywhere else.
And why would it do that? What’s the functional
significance of the fact that the plumbing is set up so that all that blood goes
to the liver first? Well, the liver is
involved in detox, so basically filters
out your blood to make sure that you have not
ingested any poisons. Thank you, liver,
for doing that. The liver also produces bile. And bile is a substance,
it produces bile, so cells inside the liver
actually build bile. Bile is an unbelievable
substance that is, also, secreted into the duodenum. It’s involved
in emulsifying fat. If you do not have enough bile,
then you will not be able to break your fats
into smaller particles so that you can absorb fat
into your bloodstream. And then you can imagine, if you can’t absorb fat
into your blood, and it just
stays in your intestines, where is it going, eventually?
Yeah, it’s going out, and so you’re going to end up
with some very interesting, basically oily poop.
Hah, that sounds attractive. Thank goodness for bile. When you hear the word bile, does it make you
think of anything else? The liver produces bile, but you know what,
the gallbladder stores bile. So, look, now this is
a super-bizarre way of drawing the gallbladder. The gallbladder is
actually found on the inferior surface
of the liver. I guess if we took
this gallbladder and stuck it up there, then it would be in a more
accurate anatomical location. But it’s smashed up
on the undersurface of the liver and the liver produces bile and that bile goes
into the gallbladder and just hangs out there until
you eat a pint of Ben and Jerry’s, at which time
your gallbladder says, “Whoa, Dude, seriously? We better throw
some bile in there, so you can digest all that fat.” Thank you very much,
Mr. Gallbladder. What else does the liver do
that you need to know about? Let’s look at the,
no, let’s do the pancreas first. So, our other accessory
structure is the pancreas, and the pancreas consists of
both endocrine and exocrine cells, exocrine. The endocrine tissue
in the pancreas, what does it do, my friends? It produces insulin,
yep, which is involved in glucose, maintaining the proper
concentrations of glucose in your blood. The exocrine portion of the pancreas produces
digestive enzymes, produces bicarbonate,
which helps increase the pH of the juice that’s coming
out of the stomach, so bicarb and enzymes. And interestingly,
now, endocrine, as we know,
by definition, endocrine structures secrete
hormones into the blood. Exocrine structures secrete
substances outside the body. Remember, the duodenum, the lumen of the duodenum is
actually outside your body, so the exocrine portion of your pancreas is just
secreting your enzymes and bicarb into the duodenum. I’m going to draw you a picture of the anatomy
of that little setup, so look and be amazed.
First of all, here’s your liver. Now, your liver has two
ducts coming out of it. There is a right hepatic duct
and a left hepatic duct. Seriously, this one must
be the left hepatic duct. This one is the right
hepatic duct. Now they combine, they join
into the common hepatic duct, true story, common hepatic duct,
all right? Now the common hepatic
duct is joined by another duct that connects to, who do you think
this green blob is? This is the gallbladder. Indeed, it is so. And this duct right here,
coming out of the gallbladder, is called the cystic duct. The cystic duct,
interestingly substances within the cystic duct can
travel toward the gallbladder or away from the gallbladder. It can go both ways,
and they combine together to form the common bile duct. That’s a lovely color,
common bile duct. Meanwhile, over here,
I’m not using that color, we’ve got our friend,
who’s this? That’s our buddy the pancreas, and the pancreas is full
of holy duct-o-rama, and the pancreas
actually has a duct that joins with the common
bile duct. And where do they dump? Let’s go with a lovely,
hmm, we’re running out of
colors here, purple. Who is purple? This right here
is like an opening that everybody is dumping in. Everybody’s going
in this opening. This is my duodenal papilla. That gives it away. Papilla, and who is this?
Where are we dumping? The duodenal papilla is found,
where? In the duodenum, right? It makes perfect sense. So bile is going to get
dumped into the duodenum and pancreatic juices
of lots of different flavors. Guess what this duct is called. I love it when it’s easy. This is the pancreatic duct.
Got it. What else do I
have to tell you about this? Ya ya ya ya ya ya,
ya ya ya ya ya. I know, there’s
some gross anatomy, gross, of the liver
that we should probably address. Okay.
So, your liver has two lobes. And we know that when we
look down at our body, left and right are switched, which means I can’t
draw on this up here because it’s actually a webpage, but this is the left
lobe of my liver, whereas this one
the right lobe of my liver. The right lobe is bigger.
Now, think, what structure is going
to be superior to the liver? The liver is actually nestled
in the superior portion of your abdominal cavity, and it’s separated
from the thoracic cavity by the diaphragm. And we’re going to talk
about the diaphragm when we get
to the respiratory system, but the diaphragm is
a skeletal muscle that basically
covers the top of my liver. What is on this side? If I keep going left,
what am I going to find? You’re going to get
to your stomach. Your stomach is over here,
and so the esophagus is actually going to pass
through the diaphragm and into the stomach,
which is next to the liver. Now there are a couple of
structures that are significant from a gross
anatomy perspective. One is this ligament,
right here, called the falciform ligament. The falciform ligament
actually connects, attaches
to the anterior body wall. And at the inferior surface of the falciform ligament,
right down here, is a structure called
the round ligament. The round ligament is like
an old-school umbilical vein. What? Do you need
an umbilical vein anymore? Do you have an umbilical cord?
No, but you used to, and you used to be attached to your Mama
through that umbilical cord, and the round ligament is
the leftovers of that attachment.
How cool is that? Check out the placement
of the gall bladder. It’s tucked up nice and tight
to the liver itself. What else?
Nothing else, that’s perfect. Now, let’s talk
about the final cavity. Let’s go into a little more
detail on the peritoneal cavity.