Week 9: Digestive pt2 Flashcards
chief cells make precursors for?
digestive enzymes in the stomach that are going help in protein digestion
parietal cells make what?
HCI acid that’s gonna be important in:
1. HCI acid converts those inactive precursors released in lumen of stomach by chief cells into their active forms
2. HCI converts pepsinoge to pepsin
pepsin starts working on breaking down what?
chemical bonds
why is low pH in stomach gonna denature proteins important?
denaturing them is gonna unfold them which makes it easier for the pepsin and other protein digesting enzymes in stomach and SI to actually break covalent bonds and make smaller pieces
parietal cells have?
carbonic anhydrase
CO2 and H2O in the parietal cells…
- carbonic anhydrase puts them together to make carbonic acid
- carbonic acid breaks down into bicarbonate and H+
what will we do with the bicarbonate and H+?
different than RBC
- H+ will get pumped into the gastric lumen against its concentration gradient
- bicarbonate is gonna go out towards blood in exchange for chloride ion (chloride shift)
- chloride channel at luminal end of parietal cell and chloride will move into parietal cell and move down its concentration gradient into lumen of stomach
- HCI i just secreted HCI acid
bicarb is gonna wind up in the blood and bicarb is a ___ base
buffer
if you put bicarb in the blood, what happens?
it can take up some H+ in the blood
what we see when we’re actively digesting, because the stomach is secreting HCI acid and you’re putting more bicarb in the blood, depending on how much HCI you’re making, what happens to the arterial pH?
right after you eat a meal, the arterial pH becomes a little higher
- not a huge change but measurable and that increase, bc we put bicarb in the blood, is called the alkaline tide?
is this going to completely disrupt your acid-base balance in your blood?
absolutely not
- not a huge change
what is the carrier that is inhibited by prilosec
H+ transporter also called a proton pump
that whole class of drug is called?
proton pump inhibitors
When reading a label on a proton pump inhibitor, it will tell you 2 things, the first thing is?
it is not gonna give you immediate relief if you have a heart burn or acid reflux
what is the second thing?
you shouldn’t take it past the certain period of time without talking to doctor
what is the reason for that?
our cells generally respond well to completely blocking something . (turning it down or up, we can adjust to) but completely shutting off a carrier thats supposed to move something out of that cell, if you do it over a long period of time, it is gonna mess things up in that cell and cause problems
when thinking about parietal cells, what is our focus generally on?
hydrochloric acid secretion
what else is coming from parietal cells?
intrinsic factor secretions
what does intrinsic factor bind?
vitamin B12
-keeps it from being digested and helps it get absorbed
what is a problem we see in people who had to have a large part of body removed?
they don’t have enough parietal cells left to make enough intrinsic factor to get them enough vitamin B12 to their bone marrow.
what condition do they end up having?
pernicious anemia
person who has pernicious anemia is not going to be able to absorb enough vitamin B12 to keep their?
bone marrow up
what else causes pernicious anemia?
lack of intrinsic factor, stomach cancer, stomach ulcers, autoimmune disease
how are you gonna control secretion?
nervous system and hormones
what is the parasympathetic system involved in?
stimulating the secretory activity of chief cells and parietal cells
what other hormone is involved in stimulating secretory activity of chief cells and parietal cells
gastrin
what is the diameter of the small intestine?
about 1 inch, 20 ft
small intestine is divided into three sections that include?
Duodenum, Jejunum, and Ileum
What does the duodenum connect to?
“connects here to the stomach with the pyloric sphincter in between”
- uppermost section of small intestine, attached to pylorus
- C-shaped
how long is the duodenum?
10 inch
where is the jejunum starts?
where the C of the duodenum ends
- begins where digestive tube turns abruptly downward and forward
how long is the jejenum?
8ft long
how long is the ileum?
about 12 inch
is there a clear indication where ileum starts?
no
small intestine is all about?
surface area
why is it surface area for secretion?
we’re gonna have to contribute things that are gonna help with final stage of digestion
why is it surface area for absorption?
most of what we absorb is going to be absorbed in small intestine
if 20ft of small intestine is not enough, there are also _____ ____________ in small intestine that will increase surface area in inner part of small intestine
three modifications
what are the three modifications?
- plicae (plica singular)
- Villi
- Microvilli (Brush border)
what are plicae?
circular folds in lining of small intestine
- you have them in jejunum, ileum, and duodenum
what are villi?
- stick up like fingers off of plicae
spaces in between villi called?
intestinal crypts
what is inside of each villus?
arteriole, venule, and lactyl
what is a lactyl?
lymphatic capillary in digestive system
what are one of the functions of the lymphatic system?
to carry lipids that the digestive system absorbed and so we get them into the lymphatic system through these lactyl’s
the villus is covered by?
an epithelial layer: simple columnar epithelium
what are enterocytes?
intestine cells
- epithelial cells that line small intestine
the enterocytes have what?
microvilli
all three modifications together do what?
increase surface area in the small intestine 100x
Plicae, villi, and microvilli are modifications of the ?
mucosa that we see in the small intestine
we dont have any of those things in?
esophagus and stomach
what are the characteristics of an epithelial tissue?
they reproduce
there are stuff moving past these villi all the time which leads to?
some possibility of friction damage and we need to be able to replace any cells that come off this layer bc the epithelia are supposed to be barriers
what happens here?
we have stem cells to replace epithelia down in the crypt and as these stem cells divide, they get moved up the crypt and eventually they get all the way to the top. the reward to getting up to the top is by getting knocked off the villus and become part of what’s getting digested or leaving body’s waste
what is the potential problem here?
it is dark in small intestine and moist and there are a lot of nutrients
- make bacteria heaven
- down in crypts, there is not much moving past and so bacteria can hang out in the crypts and kill stem cells and we could lose our epithelial barrier
down in the bottom of the crypt, we have another set of cells called?
paneth cells
what do paneth cells do?
secrete antibacterial enzymes
- they’re down in the bottom of the crypt as protection for the stem cells
- they also secrete other things that help to inhibit bacterial growth
- helps maintain a balance
what will you mainly see the small intestine produce?
water with some bicarb in it
most digestive enzymes we will use in the small intestine are either?
anchored membrane proteins that are attached to lumen end of the enterocytes or they’re things made by pancreas and put in small intestine
goblet cells contribute a little bit to the juice because?
they will make mucus to make material easier to move through the small intestine
what do we not understand?
the step by step regulation of producing intestinal juice
what do we know?
- having food in the small intestine especially in duodenum is going to stimulate some juice production and change chemical composition a little bit.
- acid in small intestine stimulate intestinal juice
why would you want more intestinal juice if you have acid or acidic contents in small intestine?
dilutes the acid
what is the hormone vasoactive intestinal peptide going to do?
- stimulate production of intestinal juice
- makes capillaries in the villi more permeable (easier for stuff to get absorbed and moved into the blood)
- gonna act on stomach to decrease gastric motility and gastric secretion
why would you want VIP to turn down gastric activity?
slow down digestion in stomach so you can continue to work what is in the duodenum
how to control intestinal motility?
intrinsic stretch reflex
what does that say?
if you stretch the duodenum/other parts of small intestine, it will increase motility from that point forward
what happens if we stretch duodenum and stuff keeps coming in from the stomach?
that stretch will cause the stuff in the small intestine to move forward faster ending up in diarrhea
what is another thing that controls intestinal motility?
CCK
with respect to intestinal motility, CCK is the only hormone that?
increase intestinal motility
endocrine cells in duodenum is going to release?
CCK into the blood when chyme arrives in small intestine that is high in fat or high in partially digested protein
how long is the pancreas?
6-9 inches long
there is a head and tail, the tail ends up behind what?
the stomach
the pancreas is a mixed gland, most of it is?
exocrine
- we’re making stuff and secreting it into ducts and those ducts open on to body surfaces
- in this case, the body surface is the lining of small intestine
the pancreas also has endocrine cells that are involved with?
storage of nutrients and stimulus to use nutrients
the head and neck of pancreas sits on?
C-shaped curve of duodenum
a duct that runs the length of the pancreas called?
pancreatic duct
where does the pancreatic duct empty into?
the small intestine, into the duodenum and in a site called major duodenal papilla
it is fairly common for people to have an accessory pancreatic duct T/F
true
this the main place that things that are being secreted by the exocrine part of pancreas will enter the?
alimentary canal
when taking closer look at the pancreas, we have are groups of endocrine cells called?
pancreatic islets
- about 2% of pancreatic tissue
the other 98% are made up of these balls of exocrine cells called?
pancreatic acini
the acini are going to empty into?
smaller pancreatic ducts that are going to come together and eventually form the main pancreatic duct thats carrying everything thats been deposited in small intestine
what do the pancreatic acinar cells secrete?
inactive precursors of digestive enzymes
they’re gonna secrete inactive precursors of things that will digest what?
digest proteins, lipids, and carbs, and nucleic acids
what are you made of?
proteins, lipids, carb, nucleic acids, some waters that don’t need digesting, and some minerals
all of this digestion that we’re performing in stomach, SI, all of this is using chemicals that could digest?
us or parts of us
what is the stomach focusing on digesting?
proteins
there is a thick mucus layer that lines the lumen of the stomach that protects us against?
the effects of the HCI acid and effects of pepsin
the pancreas is making things that when active…
could digest everything
just having some protection in the pancreas…
is not gonna be enough help
what do acinar cells secrete?
inactive things
- ending with ogen
- start with pre
- start with pro
all indicate they’re not active
where do all of those inactive things go into?
small intestine
the lumen of small intestine lined with?
enterocytes
on the enterocytes, what do we have?
membrane proteins
what are the membrane proteins called?
enterokinase
they are not released into a lumen, they are?
anchored
- part of protection here
a specific precursor molecule called trypsinogen, in the lumen of SI runs into a molecule of?
enterokinase
the enterokinase converts that trypsinogen into?
trypsin
trypsin is a molecule that digests what?
protein
the next thing that trypsin does is act on another precursor called?
chymotrypsinogen
it converts chymotrypsinogen to ?
chymotrypsin
trypsin and chymotrypsin together activate?
all the other pancreatic enzymes that will be put into the SI
physiology of that
- enterokinase leads to active trypsin
- active trypsin leads to active chymotrypsin
- trypsin and chymotrypsin activate all the other pancreatic enzymes that are now in the intestinal lumen
one of the things you learned about enzymes?
they don’t make a chemical reaction happen that would not have happened eventually without the enzyme
it is possible for the molecule of trypsinogen to get activated in the?
pancreas every now and then
- you can start that whole cascade in the pancreas
what does the pancreas do for you when working properly?
helps digest fats, carbs, proteins, secretes two hormones that regulate blood glucose levels, and storage of amino acids and lipids
if someone’s pancreas is severely damaged, what problems is it going to have?
problems taking in calories bc they can’t digest what they eat or digest efficiently
one other important substance we get from the pancreas, and it doesn’t come from the acinar cells and it doesn’t come from endocrine cells,
where does it come from?
cells that make up the pancreatic duct
- that substance is bicarbonate
the duct cells of the pancreas also have?
carbonic anhydrase
what are we talking about? the ones that make up the..
small ducts
pancreatic duct
after combining H2O and CO2 making carbonic acid, now we put the bicarb in the?
pancreatic duct with the H+ in the interstitial fluid where it will wind up in the blood
now i want the bicarb and get rid of the H+, whereas the stomach what do you want?
i wanted the H+ and get rid of bicarb
bc i’m putting H+ in the blood, when i make bicarb what happens to my arterial pH?
my arterial pH drops just a little bit
- not enough to mess up the shape of my proteins
there is a condition that we usually associate with the respiratory system that has a huge effect on the pancreas on the ability to do its job which is called?
cystic fibrosis
we think about this as someone making mucus so thick that we can’t get it out of their airways but they also don’t fully develop what?
the duct system and they wind up with pancreatitis very often bc you can’t get
- (if an enzyme could speed up a reaction, it would have happened eventually by itself. someone with a poorly developed duct system, it’s going to happen more often)
we see a lot of pancreatic issues in patients who have?
cystic fibrosis
- we start seeing the effects of those enzymes that digest proteins and carbs, and lipids, and nucleic acid actually digesting regions of pancreas
we have several hormones that are gonna get released by?
endocrine cells in the duodenum, based on characteristics of chyme that is getting delivered to duodenum
what does secretin give us?
gives us a pancreatic juice that has particular characteristics
what does secretin cause in the pancreas?
causes the pancreas to make juice that has a lot of bicarb and lower concentration of those pancreatic enzyme precursors
what can we do with bicarb?
neutralize the acid
enzymes that work in the stomach are built to work in a pH between 1-3, but we have two problems when that chyme moves from the stomach to the duodenum.
what are they?
- you don’t have the same protection in duodenum against that acid that you have in the stomach
- pancreatic enzymes that are gonna working in the duodenum and the rest of the SI and also the membrane proteins like enterokinase and enzymes that is gonna do the last little bit of digestion and proteins that are gonna help us absorb are built to work in a pH around 7
if we put chyme of pH of 1-3 into the duodenum and we don’t buffer it, what will happen?
we’re gonna damage very important tissues and we’re gonna make it impossible to finish digestion once that stuff leaves the stomach.
secretin is going to get us what?
the bicarb we need to neutralize the chyme to get the pH up near 7
two things happen bc of that pH change (w/ repect to enzymes) which is?
- it gets us in the right pH range for the pancreatic enzymes and intestinal enzymes to work
- it gets us out of the right pH enzymes for the stomach to work so they get shut off and so they denature and now they can get recycled and digested by pancreatic enzymes and we can absorb those pieces
what is the main stimulation for release of secretin?
low pH chyme in the duodenum
there are two other things that secretin is gonna do for us
- secretin can cause gallbladder to contract. (not main hormone that will do that)
- secretin decreases gastric motility and gastric secretion
4 hormones that come from the duodenum
- gastric inhibitory peptide
- vasoactive inhibitory peptide
- CCK
- secretin
all four hormones do what to gastric motility and gastric secretion?
decrease
all the other things that are controlled by those hormones depend on?
not overwhelming the duodenum
CCK is another hormone that is important in controlling the?
pancreas
also gallbladder
what does CCK mean?
protein that works the gallbladder
what does the CCK do to the pancreas?
effect the characteristics of the pancreatic juice
CCK is gonna cause the pancreas to produce what?
a juice that is lower in bicarb and higher in enzyme content than what we get from secretin acting on gallbladder
secretin is the main hormone that is gonna?
get us buffered chyme
CCK is the main hormone that is gonna get us?
the enzymes we need to digest what isn’t digested from the chyme that just moved from the stomach into the duodenum
even tho the stomach is digesting protein, it’s not breaking them down into?
individual amino acids and that is what we need to get
CCK is the main hormone that is also gonna get us?
gallbladder contraction
what else does it do?
decrease gastric motility and gastric secretion
- not that we have CCK, we’re sending out the conditions to let us finish digesting
what happens if you put too much stuff in the duodenum?
increase gastric motility and you move that stuff out and you won’t get to digest it and so we won’t be able to absorb it
overall functions of the pancreas
- production and secretion of digestive enzyme precursors
- production and secretion of insulin
- production and secretion of glucagon
where is the bicarb coming from?
pancreatic duct cells
in a normal healthy adult, the liver weighs?
3-4 Ibs
what is the largest organ in body?
liver
- skin is the biggest surface area wise but liver weighs more than the skin and the skin is on your body rather than in your body
the liver is divided into how many lobes?
2 lobes
- right and left lobe
left lobe is how much of the liver?
1/6th of liver
the right lobe is how much of the liver?
5/6th of liver
the two lobes are divided by?
falciform ligament
right lobe is divided into 3 which include?
Right lobe proper
caudate lobe
quadrate
55:15
the gall bladder is attached to where of the liver?
posterior surface of the liver
the liver is made of?
lobules
what are lobules?
small blood vessels and fibrous strands
the lobules have how many sides?
5 or 6
what are hepatocytes?
liver cells
there are plates of these liver cells, in between the plates of the liver cells are?
sinusoids
what is in the center of each lobule?
a central vein
out in the corner of each edge of hepatocyte, what do we have?
a branch of hepatic portal vein
branch of hepatic artery
and branch of bile duct
the blood that’s coming into the liver from hepatic portal vein is coming from where?
both intestines, stomach, and spleen
in that blood, what do we have?
al the water we absorbed
minerals we absorbed
everything we absorbed that isn’t a lipid
where is all of that material gonna travel?
from branch of the portal vein and through the sinusoids
it’s being examined by ?
hepatocytes
- they are taking stuff out, putting stuff in
where does the blood go after?
in the central vein of the lobule
the central veins are gonna come together and eventually form?
a hepatic vein that empties into the IVC
what is the branch of the hepatic artery there for?
it’s gonna give us oxygen to the hepatocytes and lipids to help keep them alive
- we need oxygenated blood to keep those hepatocytes alive
- the blood from the portal vein branch is gonna have plenty of nutrients but no lipids bc those are in the lymphatic system
what will happen to the blood in the portal vein and blood from branch of hepatic artery?
they’re gonna mix in the sinusoids which it will all go into the hepatic vein into the IVC
blood from portal vein travels from?
outside and into the center
blood from branch of hepatic artery is traveling from?
outside and into the center, to the central canal
in the branch from bile duct, stuff is being brought where?
to it
what is one of the jobs of hepatocytes?
make bile
green circles are spaces between the hepatocytes and the spaces are closes off by?
tide junctions
- that is where the hepatocytes put the bile they’re secreting
where does the bile move through?
tiny bile ductules and out to the branches of the bile duct
sinusoids in the liver are one of the places that we start to recylce what?
old RBC
- sinusoids are windy and older RBC not flexible causing them to get stuck in the turns of the winds of sinusoids
what is another player that can eat those RBC and anything else that would get stuck in the sinusoids and liver lobules
phagocytic cells
those phagocytic cells are called
Kupffer cells
coming out of the left lobe of the liver, what do we have?
left hepatic duct
- anything in the pic that is green, is carrying or storing bile
coming out of the right lobe, what do we have?
right hepatic duct
they’re gonna come together and form what?
common hepatic duct
the gallbladder has the cystic duct, and where the cystic duct and common hepatic duct come together, what does that become?
common bile duct
common bile duct carries what and empties into what?
bile; small intestine at the major duodenal papilla
- same place that the pancreatic juices go in
one of the functions of the gallbladder is?
store bile
how do you get bile to go up in here?
- if you wanted bile to go this way instead of this way, make it easier for bile to go this way than this way. if pressure is lower to go in here, it’s gonna go there. if its lower pressure to go down and into the SI, it will go into a common bile duct to go down
- there is a sphincter there
