Lecture 8: The Digestive System pt. 2 Flashcards
What does Metabolic Regulation consist of?
The liver impacting what is available in the blood for use of energy
The liver is one of the two main organs that determines what?
The composition of your blood?
What is the other composition?
Kidneys
What is specific function #1 under Metabolic Regulation?
The liver has a huge role in carbohydrate metabolism.
The organ in your body that has the most impact of regulating blood glucose levels is your liver. Why?
Bc liver decides whether to store glucose or carbohydrates that are coming in from digestive system. Whether to let them go bc we’re at the level we need, or whether we need to break down glycogen and put that glucose in the blood.
What affects the carbohydrates that are passing by?
Insulin and Glucagon.
How can the liver increase blood glucose cells?
- Break down glycogen
- take amino acids and make them into glucose (gluconeogenesis)
Both of those happen under control of what?
Glucagon (which raises blood glucose)
How can we lower blood glucose?
Insulin will stimulate liver to take glucose out of the blood, and store it as glycogen. (NOT throwing it away, we store it until we need it later)
The liver is also important in what?
Lipid metabolism
When your digesting lipids in the small intestine. We need to do things to increase the surface area. But once those things get absorbed into an intestinal cell, what happens?
We get a chylomicron.
What are in chylomicrons?
They have cholesterol, triglycerides, fatty acids in them.
What are chylomicrons made by?
They are made by enterocytes and put them in lactyls.
Where are the chylomicrons going?
They are going into the lymph and wind up in the thoracic duct and into the left subclavian vein.
What does this mean?
That the chylomicron is in the blood and gradually, all these things are going to pass through the liver.
When they get to the liver, the liver is going to do a couple of things to the chylomicron. What will the liver do?
- The liver changes the proteins
- liver removes triglycerides
- add cholesterol
This new thing that the liver just made from a chylomicron is now called a…
Low density lipoprotein
What happens to this LDL?
It’s going to be put in the blood as a system to deliver cholesterol to cells that need OR pick up excess up cholesterol from cells that need to get rid of stuff
Why is LDL bad?
LDL can be incorporated into plaques and arteries and help obstruct a blood vessel.
The proteins will be changed again to a High Density Lipoprotein. What happens to a HDL?
Cells can take or add cholesterol where it will go back into the blood and back into the liver to store cholesterol.
Where are LDL made from?
made in Liver
Where are HDL made from?
made in cells that are not Liver cells
What are enterocytes?
Epithelial cells of the intestine.
The next thing the liver is metabolically involved in is…
(Metabolic Regulation #3)
amino acid metabolism.
The liver monitor if there are too much or too little amino acids of a particular type.
What is one way that the liver can affect amino acid concentration in the blood.
Gluconeogenesis
What happens if we have too much but not enough glucose in the blood?
We convert amino acids in glucose (gluconeogenesis)
What is the metabolic regulation #4?
waste product removal
Hepatocytes that are on either side of the cytosoid are chemically examining whats in the blood moving past them. Things that could be harmful can have a couple of things happen to them…
Hepatocytes might take them in and change them into something else, might take them in and store them, take them and chemically change them and put them in the bile to leave the body.
This is the body can clear some drugs. Some drugs can be take out of the blood from the kidneys. What are the examples of two different drugs.
Tylenol: If take too much, can fry your liver. Bc hepatocytes take it in and try to hold it all and it damages it.
A drug that is not cleared by the liver but cleared by the kidneys is…
Naproxen
The last Metabolic function are…
storing minerals and storing fat soluble vitamins
What does it mean to store fat soluble vitamins?
The fat that we can store in fat soluble vitamins means its possible to accumulate too much of them
What happens when you have too much of a particular mineral or a fat soluble vitamin?
you will store it
What happens when there’s not enough in the blood?
the liver will release some of those storage supplies back into the blood to keep the levels consistent.
What consists of Hematological Regulations?
- Phagocytosis and Ag Presentation
- Synthesis of Plasma Proteins
- Removal of Circulating Hormones
- Removal of Abs (antibodies)
- Removal of storage of Toxins
- Synthesis and Secretion of Bile
What is the main digestion function of the liver?
Production of bile to emulsify fats to digest them
What is the only organ in the body that makes bile?
The liver!
The things we use to emulsify fats to keep them as tiny droplets instead one big fat drop is…
something that has a hydrophobic side to face the fat droplets and a hydrophilic to face the water environment that it’s in.
What gives color to the bile?
Biliverdin and Bilirubin. They are color pigments.
What are one of the things you may see when someone has an obstruction in the bile duct?
They have gray feces.
what give feces the characteristic brown color?
The biliverdin and bilirubin
What shape is the galbladder?
Pear shaped
How long is the galbladder?
7-10 cm long
What are the functions of the gallbladder?
- stores bile
- concentrate of bile
- eject bile
How much bile can the gallbladder hold?
30-50 ml of bile
True or False?
The gallbladder is part of the alimentary canal?
FALSE
The gallbladder is an accessory organ and food SHOULD NOT be found in the gallbladder.
The wall of the gallbladder has a mucosa, musclular layer, and serosa layer. In the mucosa, we have…
rugae
Why do we have rugae in the gallbladder?
We get more surface area to absorb water AND
It’s a muscular bag, it’s going to stretch a little bit. As it gets full, having the rugae will keep the lining from tearing.
Inflammation of the gallbladder is called?
Cholecystitis
Gall stone formation is called what?
Cholelithiasis
You can accumulate stones in the gallbladder where a person gets a flare up of pain. What are some ways?
You can block the cystic duct or the common bile duct. OR pancreatic duct and common bile duct this last little piece to have their contents enter the small intestine through the duodenal papilla. A stone there can cause all sorts of problems bc it can block bile from getting into the intestine, but it can block those pancreatic enzyme precursors that will accumulate enough sometimes to actually have one molecule of trypsinogen to trypsin and now we’re digesting the common bile duct and back up the pancreatic duct. (NOT GOOD)
What can lead to gallbladder removal?
Gall stone formation or Cholelithiasis
What are the risk factors for having gallbladder trouble?
To cause gallbladder trouble:
- fat
- female
- 40
What happens to the control of bile if somebody has their gallbladder removed?
- no storage
- no concentration
- bile that was continually made by the liver is going directly into the small intestine
By not having the concentration of the bile and not having control of how much bile we have available at any given time, what would you see in someone not having their gallbladder removed?
Lipids going into the small intestine are going to get you more CCK which increases your intestinal motility and will experience gastric dumping.
Someone who has their gallbladder removed is supposed to be on a low fat diet. Why?
To avoid that problem of having what you just ingested leave the body very quickly b4 you have time to digest enough it
What is jaundice?
yellow discoloration of skin (or eyes)
what can cause jaundice?
- problems with the liver
- obstruct the bile duct, there is no place for the bile to go that’s been made by the liver and it starts going into the sinusoids so it gets into the blood
CCK and secretion both have the ability to cause…
the gallbladder to contract and eject bile that’s been stored in the gallbladder
CCK also stimulates…
the liver to make more bile
What are the Intestinal Hormones?
- Gastrin
- Secretin
- gastric inhibiting hormone (GIP)
- cholecystokinin (CCK)
- Vasoactive Intestinal Peptide (VIP)
- Enterocrinin.
Where does Gastrin come from?
Stomach
Gastrin is also released by…
Duodenum
Gastrin from the stomach is released because of…
- vegus nerve stimulation
- there’s food in the stomach
- thinking about eating
There are cells in the Duodenum that release Gastrin. The chyme that moves in the small intestine has a lot of protein in it. What does this mean?
That’s a signal that you didn’t digest enough protein. That signal is going to get us more gastrin to crank up the motility of secretion of the stomach.
It is the ONLY hormone on this list that INCREASES gastric motility and gastric secretion.
If you have chyme move from the stomach to the duodenum that is rich in fat…
you’re not going to get gastrin secretion.
If you have chyme move from the stomach to the duodenum that is rich in carbohydrates…
you’re not going to get gastrin secretion from the duodenum.
The primary job of Secretin?
Get you pancreatic juice that is high in bicarb and low in enzymes so you can buffer the chyme that just arrived from the stomach.
Secretin will…
- make the gallbladder contract
- decrease gastric motility and gastric secretion
Gastric Inhibitory Peptide gets secreted from…
the duodenum when you get chyme that’s high in carbs or high in fat
GIP stimulates…
insulin release.
GIP inhibits (decreases)
gastric motility and gastric secretion
Vasoactive Intestinal Peptide (VIP) is going to be released when…
you get any type of chyme in the duodenum.
You get more secretions from the intestinal glands that give us mucus. But they give us watery secretional bicarb as well.
They increase the permeability of capillaries in the villi, so it’s easier for what we have absorbed to get to the blood.
What else does it do?
decrease gastric motility and gastric secretion
Enterocrinin is a hormone released when
any type of chyme gets to the duodenum.
What does this do?
It stimulates mucus glands, specifically.
When talking about absorption, one of the things that gets absorbed is water. If we are absorbing water…
the material that’s been liquid is getting to be progressively more solid and that mucus is going to be necessary to keep that material moving out the small intestine into large intestine and out of the body.
CCK is going to be released when
-lipids & fats in the chyme
-when we have partially digestive protein in the chyme
When we have those things in the chyme, what we need is a bunch of pancreatic enzymes or inactive precursors of those enzymes. CCK gets us those pancreatic juice…
that is high in enzyme and low in bicarb
CCK stimulates…
- intestinal motility
- cause gallbladder contraction
it is a satiety factor
What does satiety factor mean?
tells you to stop eating when you’re full
What else does CCK do?
decreases gastric motility and gastric secretion
All these hormones are coming from where?
Duodenum
All these hormones that are being released in response to…
local effects / local factors in the duodenum
Why is the large intestine called the large intestine?
Bc the diameter is much bigger than small intestine
How big is the large intestine?
5-6 ft in length, diameter is about 6 cm
Sticking off the cecum is called…
Vermiform Appendix
Vermiform means…
warm light??? (2:01:29)
Where the ilium connects with the cecum, there is a sphincter muscle.What is that called?
The ileocecal valve
What is the job of the ileocecal valve?
keep too much material from going from the large intestine back into the ilium
As we go up out of the cecum, there is the ascending colon. The ascending colon ends where?
At 90’ turn called the hepatic flexure
The transverse colon extends from…
hepatic flexure over to splenic flexure
What is Taeniae Coli
band of longitudinal smooth muscle in the wall of the small intestine
The sigmoid colon connects to
the rectum and then connects to the anus
In the large intestine, there are modifications in the tube that we see different in the small intestine. We don’t have plicae, villi, and microvilli here. What we do have is
simple columnar epithelium
We don’t have a
complete circular layer of smooth muscle and a complete longitudinal layer of smooth muscle.
Instead of having a complete circular layer, we have these regions where we have a small circle…
a band of circular muscle
The sections between the bands of circular muscles are
Haustra
When you get to the rectum, we don’t have all 4 layers. The rectum is going to end in a structure called
Internal anal sphincter
When you look at the wall of the small intestine, there is a lot more goblet cells. Why?
Bc by the time, the material gets to the large intestine, most of the water that’s gonna get absorbed out of it is already gone and we need mucus to make this stuff slippery.
What are the functions of the large intestine?
- absorption in the large intestine
-movement in the large intestine
-defecation
What happens in absorption in the large intestine?
- < 10% of the absorption that happens in digestive tract happens in the large intestine.
- Absorbs Vit. K , Biotin, Vit. B5
- About 20% bile salts get absorbs in large intestine and get back into hepatic portal vein and go back in the liver and get used again in the bile
- Most of what gets absorbed in the small intestine is water
What is the main function of the large intestine?
Formation of feces
Is Defecation a reflex?
Yes
What is defecation triggered by?
receptors in the wall of the rectum
In the small intestine, we have peristalsis and segmenation. In the large intestine, we have something different. What is it?
Mass movements
Instead of moving chyme from here to there, a Mass Movement…
happens less frequently but it moves the fecal material much farther in one wave of motility.
We start with the rectum empty and then the wave of mass movement moves…
fecal material into the rectum and that stretches those receptors in the rectum.
This will do two things. What are they?
- stimulate more mass movement
- stimulate the urge to defacate
As you start to accumulate fecal material in the rectum, what happens?
it puts pressure on the internal anal sphincter.
We don’t have any voluntary control of the internal anal sphincter and pressure on that sphincter…
makes it relax. Which lets the fecal material put pressure on the external anal sphincter which is under voluntary control.
As fecal material sits in the colon…
more and more water gets absorbed and so the fecal material is getting more compact and harder to move.
Digestion applies to…
anything that helps you to physically or chemically break things from big or complex chunks into smaller and less complicated chunks
What is included in mechanical digestion?
- chewing
- peristalsis / segmentation
- moving material through the alimentary canal
- mixing material in small intestine to bring what you digested in contact with the wall to be absorbed.
Chemical digestion is all about…
using enzymes to chemically break bonds.
Most of the chemical digestion is going to happen by hydrolysis. What does this mean?
We use water to break covalent bonds. Since enzymes are proteins, we need to have the right pH in the area for a particular enzyme is supposed to work.
The 6 main nutrients that a human is going to absorb are:
- carbohydrates
- proteins
- fats
- water
- minerals
- vitamins
The only ones we need to digest are:
proteins, carbohydrates, and fats
The last bit of digestion that happens to proteins and carbohydrates is called…
Contact digestion
We got something that used to be a long complicated protein and now it’s broken it down to chunks of two or three amino acids. The last part of breaking it down into amino acids are accomplished by…
enzymes that are membrane proteins on the enterocytes.
So to have that last bit of digestion happen…
you have to make contact with the wall cause that’s where the enzymes are. They are anchored.
The reason you want that to happen right next to the wall…
bc that’s where the carriers are that are going to absorb this stuff.
How do we get this stuff into the body?
If you want to absorb glucose, I have a carrier that carries a Na ion and Glucose molecule in the same direction. It’s passive transport that is powered by a sodium gradient. The sodium in the lumen is > the sodium in the enterocyte so sodium moves down its concentration gradient and it brings glucose in. The glucose and the sodium are both bound to the carrier molecule (NOT TO EACH OTHER).
In order for this to keep happening, sodium co -transport ,
I have to maintain sodium gradient. I have to take sodium from a place where it’s in low concentration and move it to place where it is high concentration (Outside the cell). To do that, I use ATP. This is called Secondary Active Transport).
If I need to absorb an amino acid, sodium co- transport.
To make sure I maintain the sodium gradient, I pump the sodium out and use some ATP. I have one of these carriers for every individual amino acid.
Absorbing Sodium and different monosaccharides moves particles…
from the lumen to the blood.
Absorbing sodium and amino acids moves
particles the lumen to the blood
Moving those particles make…
an osmotic gradient that drives water reabsorption.
When is the glucose absorbed?
When it goes into the blood. It has to cross the epithelium.
What gets absorbed in the stomach?
- Water
- Short chain fatty acids
- ethanol
What does the small intestine absorb?
- water
- carbohydrates
- proteins
- lipids
What does the large intestine absorb?
- water
- lipids
- vitamins (fat soluble vitamins)
Every place that has absorption…
every one of those places have water absorption.
Why do you need to know where these things get absorbed?
When someone has surgery and they have their small intestine taken out, particular vitamins / lipids aren’t going to be absorbed.
You are going to have different deficits in a patient that has some part of their digestive tract removed or a patient that can’t take food by mouth. It affects what can get absorbed or how effectively it can get absorbed.
