Secretions Flashcards
Where does most of microbial digestion take place
In the large intestine
What kind of environment is needed for most digestion to take place
Need a warm moist environment
True or false microbial digestion is enzymatic digestion
True: it is because microbes also use enzymes to break down nutrients
What are the end products of digestion in the large intestine
Volatile fatty acids
What are the 3 common volatile fatty acid products of large intestine digestion
- Propinate
- Acetate
- Butyrate
What are short chain (volatile fatty acids) for animals (what do they act as)
They act as an energy source after absorption
What is the general ideal pH for digestion
Close to a neutral pH
How does the gut maintain a generally neutral environment, why does it have to do this
It constantly removes volatile fatty acids since they are acidic and the Ideal pH for digestion is close to a neutral pH
What is the retention time like in the large intestine compared to the small intestine
The large intestine has a longer retention time than the small intestine
Large (1 day) Small (~2-3hrs)
At what pH do short chain fatty acids form (what is their pka)
They form at a neutral pH
Pka = 4.5
What is the purpose of adding a hydrogen to charged SCFA’s
To make them non-polar so that they can cross the membrane via diffusion
What are the 2 ways that SCFA’s are absorbed, describe them
Non-ionic diffusion: the use of transporters in the small and large intestine for SCFA’s to diffuse across the membrane
Apical: the use of bicarbonate exchange to move SCFA’s across the membrane
Why is it so important that calves get immune transfer from the milk
Because calves do not get immunoglobulin transfer through the uterine wall
What is the majority of calf death due to
Failure of immune transfer
How does passive transfer of immunity through colostrum occur, describe this process
By nonspecific pinocytosis
The use of vesicles to transport materials across the membrane
What is the challenge with pinocytosis and immune transfer
The rate of pinocytosis after birth drops very quickly
Which decreases the rate of immunoglobular absorption also decreases quickly
What is the preferred energy source for cells in the rumen and gut lining
What does it do for… gut development and pinocytosis
Butyrate
Accelerates gut development
Decreases pinocytosis
What are the four key aspects (things) about passive transfer (immunity)
- Timing is important
- Pinocytosis capacity is limited (amount of IgG abs)
- Many factors affect colostrum quality
- Pinocytosis is not selective
What does the presence of celiac do to the microvilli in peoples guts that have celiac disease
It damages their microvilli in their gut
What is the formula for gut secretion
HCO3- + H+ (—) H2CO3 (—) H2O + CO2
Where does the H come from and where does the HCO3 come from in the chemistry of gut secretion equation
H comes from gastric secretions
HCO3 comes from pancreatic secretions
Where does the H come from and where does the HCO3 come from in the chemistry of gut secretion equation
H comes from gastric secretions
HCO3 comes from pancreatic secretions
What enzyme catalyzes the equation for the chemistry of gut secretion
Carbonic anhydrase
What is the purpose of salivary secretions in the chemistry of gut secretion
They neutralize acidic substances
What are the salivary glands and ducts associated with
It is associated with the mandible
What species do not have amylase secretions
Ruminants and carnivores
What is the composition of a salivary secretion
- HCO3 (bicarbonate) and H2PO4 (buffers)
- Sodium and Chloride
- Amylase (except in ruminants and carnivores)
What is the function of salivary secretions
To moisten food and facilitate mastication and deglutition
Also neutralize stomach contents (what is going in and coming out) back up
What is deglutition and what is mastication
Deglutition: swallowing
Mastication: chewing
What type of cell produce enzymes in salivary secretions
Acinar cells
What controls salivary secretions
Cholinergic stimulation and Acetylcholine
Controlled by salivary center in medulla (reflex stimulation by mechanoreceptors in mouth and stomach)
What can negatively impact salivary secretions
Fear and negative regulation on the medullas salivary center
What study represents salivary reflex action
Pavlov’s dogs
Where is food stored in the body
In the stomach
What does the stomach secrete (what kind of cells secrete this)
What is their purpose
It secretes HCl (comes from parietal cells) —) change pH
Mucin cells (mucus) protect stomach from acidic environment
What kind of cells produce pepsinogen, where are they found
Why is this important
Chief cells
In the stomach
Important for digesting proteins
What aspects of the stomach are important in digestion absorption and secretion
- storage of food
- secretes HCL
- Mixes foods
- involved in digestion of proteins (secretes pepsinogen)
- is bacteriostatic
- intrinsic factor (vit B 12)
What does bacteriostatic mean in regards to the stomach
The stomach has a pH level around 2 which kills most bacteria
Why is intrinsic factor important in the stomach
It is secreted by the stomach and it is important for absorption of vitamin B 12
How do stomachs vary
- size
- acidity of environment
- proportions
What part of the stomach secretes acid???
Fund us and corpus (proper gastric)
What part of the stomach is really small in humans and dogs but really large in pigs
The cardia non glandular
What part of the stomach is the stratifies squamous epithelium
What part of the stomach is cardia nonglandular cells
What part of the stomach is the proper gastric part
The esophageal part
Cardia
Fundus and corpus
What does the cardiac region region of the stomach secrete
Mucus
What does the proper gastric part of the stomach secrete
List the cells that secrete each
- chief cell (to lumen): pepsinogen
- parietal cells (to lumen) secrete HCl
- intrinsic factors to facilitate vitamin B 12 absorption in the ileum (end of small intestine)
What does the pyloric part of the stomach secrete
Mucus and gastrin —) gastrin goes into the blood
Gastrin is important in signalling
What type of cells produce gastrin
What activates these
G cells
Proteins and peptide recognition
What does bacteriostatic mean
It means that it has a pH that kills most bacteria (usually a pH ~2)
What activates pepsinogen
What secretes it
HCl which is secreted by parietal cells
What are the 3 stimulators molecules for acid production in the stomach which cells produce them
What is the inhibitory molecule in the stomach
Acid Production Stimulators
1. G cells —) secrete gastrin
2. Activates paracrine cells —) secrete HCl
3. Activates enterochromafin cells which secrete histamine
Acid Production Inhibitor: somatostatin (activated by low pH or high acidity)
What are the three inhibitors discussed in class that are used for acid control
- Atropine
- Cimetidine
- Proglumide
What do parietal cells need to do in order to start producing acid???
They need to take vesicles that are on the inside of the cell and move them to the surface of the cell
What is mucus secretion increased by
- Cholergic stimulation (stretch)
- Mechanical stimulation
What is bicarbonate secreted by, what happens to it
It is secreted by epithelial cells
It gets trapped in the mucus gel
What is the main cause of ulcers in humans
What is interesting about it (why did it take a long time to find it as the cause of ulcers)
What kind of environment does it require
What other animal does this effect
Who figured this out?
- Helicobacter pylori
- It is also found in 80% of healthy people
- Need acid and increases stomach pH
- It can also affect pigs
- Barry Marshal
- What initially activates acid secretion in the stomach
- What cells secrete the acid and how are they activated
- What inhibits acid secretion what initiates it release
- Distension (stretching)
- a. Starts with Acetylcholine activating a neural reflex
b. Which activate parietal cells which secrete
c. Which activate G-cells which secrete gastrin
d. Which activate enterochromafin cells which secrete histamine - High Acidity or Low pH levels activate somatostatin which inhibits (G-cells, enterochromafin cells, and parietal cells)
—) this brings the pH back to 2 (its original pH)
What is the formula that you need to know for acid neutralization
HCO3- + H- (—) H2CO3 (—) H2O + CO2
During acid neutralization what substances go where
(to the blood or to the gastric lumen)
H and Cl —) gastric lumen
HCO3 goes to blood while Cl goes into cell
What are the clinical signe of stomach ulcers
- Pale animal
- Breathlessness
- Dark feces
- Vomiting
- Weight loss
Is helicobacter zoonoti
Yes
What do fine particles and high moisture mean for gastric ulcers
It means that an animal can be more succeptible to gastric ulcers
What are some factors that can increase the risk of stomach ulcers
- fine particle food
- stress
- mineral imbalance in feed
- immunity function
- microbial factor (helecobacter suis)
What are exocrine secretions
Enzymes —) mostly proenzymes
Do pancreatic secretions vary across species
Yes they do
What are exocrine secretions
What are the key cells for these secretions what do they do
They are enzymes (mainly pro enzymes)
Key Cells
1. Acinar cells —) create proenzymes and package them into vessicles
2. Duct cells —) produce and secrete bicarbonate (important for balancing pH)
Where does bicarbonate come from
Where is this structure located relative to other structures
- It comes from the pancreas
- It is located right next to the duodenum which is found right next to the pyloric sphincter that enters the stomach
What is the substrate and effect of each enzyme listed
1. Trypsin
2. Chyme trypsin
3. Elastase
4.Carboxypeptidase
5. Lipase
6. Phospholipase
7. Amylase
8. Ribonuclease
9. Deoxyribonuclease
1,2,3. Proteins and peptides, cleaves interior peptide bonds
4. Proteins and peptides, releases a.a.’s at carboxy terminal
5. Phospholipids, cleaves the ester bond at the 2 position of phospholipids
6. Polysaccharides, cleaves starch and glycogen to maltose and short chains
7. RNA, cleaves RNA to ntd.’s
8. DNA, cleave DNA to ntd’s
What activates zymogens (inactive enzymes)
Proteases which cut the amino acid bond
What is pancreatic exocrine insufficiency
- what causes it
- what are the symptoms
- how do you test for it
- what breed(s) is it most common in
- usually because the animal’s Acinar cells have died —) make enzymes —) no enzymes = no food digestion
Symptoms - weight loss
- greasy fouls smelling diarrhea (no proper fat digestion)
- dry dandruffs coat
Testing
- blood test for trypsin-like immunoreactivity
- stool test for protease and elastase (old school)
German Shepard and rough collies
When an animal has exocrine pancreatic insufficiency why do they have very bad smelling diarrhea
Because they would have improper fat digestion
Why are dogs that are treated for exocrine pancreatic insufficiency sometimes given antacids
—) because we don’t want the enzymes that we have given them to become denatured
Is EPI genetic in both dogs and cats
What are the causes of EPI
What is it often associated with
- it is genetic in dogs but not cats
Causes - Chronic pancreatitis (long term swelling of pancreas cells)
—) often results in cell attacking the wrong things
—) leads to the obstruction of the pancreatic duct (cancer or tumour) - Often associated with bacterial overgrowth or duct blockage
What is crypt enterocyte secretion what does it secrete
- what does it provide
- what is it induced by
It secretes Cl, Na, and water
It provides the electrochemical gradient that is needed for amino acid and glucose absorption
Induced by: ACh, Prostaglandin, and serotonin
What enzyme is involved in acid neutralization
Carbonic anhydrase
what are the 8 steps in the mechanism for water secretion (paper)
- Stretch activates acetylcholine (ACh) release
- ACh activates G-protein release
- G-protein activates (enzyme) which releases IP3
- IP3 causes the ER to release Ca2+ into the cell
- Ca2+ pairs with calmodulin
- Ca2+ and calmodulin activate a Cl transporter protein
- which transports Ca out of the cell
- Na and water follow Ca out of the cell and are secreted
What happens with abnormal water secretion
- what are the different kinds
PGE2 (prostaglandin) is released and causes excess Ca secretion from ER which causes Cl to flow out of cell and Na and water follows
Substrate permanently attached to G-Protein which creates cycle GMP either from ATP or GTP which causes Ca to be secreted from ER (cause of secretory diarrhea)
Can be from
- cholera toxin
- toxin induced diarrhea
- enterotoxigenic Ecoli
What can cause blunted microvilli (villi) in the gut
Viral diarrhea or nutrients diarrhea
