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65 Cards in this Set

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When chyme is delivered into the small intestine, gastric emptying is slowed by what?
Hypertonic solutions;
HCl (pH < 3.5);
Fatty acids or monoglycerides;
Amino acids and peptides.
As a result of control mechanisms in the intestinal phase, the rate of gastric emptying does not exceed the rate at which .... ?
Acid can be neutralized;
fat can be emulsified;
the small intestine processes chyme.
Where does pancreas excrete its juice?
Into the lumen of duodenum.
What does the secretion of pancreas consist of?
Aqueous component that is high in HCO3- and an enzymatic component.
What is the function of pancreatic secretion, an aqueous component that is high in HCO3- in the duodenum?
It neutralize H+ delivered to the duodenum from the stomach.
What is the function of enzymatic portion of secretions of pancreas into the duodenum?
Digesting carbohydrates, proteins, and lipids into absorbable molecules.
In the pancreas enzymes are secreted by which cells?
Acinar cells.
In the pancreas aqueous component is secreted and modified by which cells?
By centroacinar cells. And modified by the ductal cells.
Most enzymes required for digestion of carbohydrates, proteins, lipids are secreted by which part of gastrointestinal system?
By the pancreas.
Which enzymes are secreted by pancreas?
Proteases, lipases, amilase.
Which two enzymes are secreted in active form by pancreas?
Lipases and amylase.
Which three enzymes are secreted by pancreas in inactive form?
Trypsinogen
Chymotrypsinogen
Precarboxypeptidases
Name one example of enzyme that is secreted by pancreas in inactive form to the duodenum.
Trypsynogen that is converted in the interstitial lumen to its active form, trypsin.
Are the enzymes secreted in the pancreas to the lumen of the duodenum right away after synthesizing or they are being stored?
They are being stored in the zymogen granules until a stimulus (e.g. parasympathetic activity or CCK) triggers their secretion.
What is aqueous component of pancreatic secretion composed of?
It is an isotonic solution containing Na+, Cl-, K+, and HCO3-.
Which cells of the pancreas produce the initial aqueous secretion?
Centroacinar and ductal cells.
Where is initial aqueous secretion of pancreas modified in?
It is modified by transport processes in the ductal epithelial cells.
Which channels do epical membrane and basolateral membrane of panctiatic ductal cells contain?
Apical membrane contains Cl-/HCO3- exchanger, Cl- channel, and basolateral membrane contains Na+/K+ ATPase, an NA+/H+ exchanger, and K+ channel.
What are endocrine secretions of the pancreas?
Insulin and glucagon.
What are exocrine secretions of the pancreas?
Salts and water and enzymes.
What are the functions of salts (HCO3- and NaCl) and water of the pancreatic juice?
To create a right environment for enzymes to work.
What is the name of inactive form of enzyme?
Zymogen.
Name three zymogens secreted by pancreas.
- Trypsinogen
- Chymotrypsinogen
- Precarboxypeptidase.
Which epithelia in pancreas structure is leaky? Acinar cell epithelia/Duct-lining epithelia?
Both are leaky.
In sum, what is happening in the duct cells of the pancreas?
Net secretion of HCO3- and net absorption of H+.
What is the effect of flow rate on composition of pancreatic juice?
Na+ and K+ compositions stay the same, but at high flow rate the HCO3- concentration is highest and the Cl- concentration is lowest. At lowest flow rates, HCO3- is lowest and Cl- is highest.
What are two functions of pancreatic secretion?
1. Secretion of enzymes that are necessary for digestion;
2. Neutralisation of H+ in the chyme delivered to the duodenum from the stomach.
What stimulates secretion of aqueous portions of the pancreas?
By the arrival of H+ in the duodenum.
What stimulates the secretion of enzymes from the pancreas?
By products of digestion (small peptides, amino acids, fatty acids).
In which stages is pancreatic secretion divided?
Just like gastric secretion, to 3 stages: Cephalic, gastric, intestinal.
What is gastric phase of pancriatic secretion?
It is initiated buy smell, taste, and conditioning and is mediated by the vagus nerve. The cephalic phase produces mainly as enzymatic secretion.
Shortly describe gastric phase of pancreatic secretion.
the gastric phase is initiated by distension of the stomach and is mediated by vagus nerve. The gastric phase produces mainly an enzymatic secretion.
Shortly describe intestinal phase of pancreatic secretion.
Most important phase, accounts for 80% of pancreatic secretion. Both enzymatic and aqueous secretions are stimulated. The hormonal and neural regulation of the acinar and ductal cells is in the intestinal phase.
What is the most important stimulant for enzymatic secretion of the pancreas?
CCK.
How is Cl- transported through acinar cells of the pancreas to the lumen of the acinus?
The Na+/K+/2Cl- cotransporter (NKCC) accumulates Cl-ions intracellularly driven by Na+ gradient. Then, Ca++ activated Cl- channels in the apical membrane provide a pathway for Cl- to exit the cell into the duct.
In acinar cells of the pancreas do Na+ ions are transported transcellular or paracellular?
Paracellular. Cl- ions in the lumen draws Na+ ions and water in.
Fill in ions in the processes of duct epithelial cell of the pancreas.
Fill in ions of secretion of HCl of pariental cells in the stomach.
What are proteases for the following zymogens:
Trypsinogen
Chymotrypsinogen
Precarboxypeptidases
Trypsin
Chymotrypsin
Carboxypeptidases
What is the purpose of bile?
Bile is necessary for the digestion and absorption of lipids in the small intestine.
Why lipids pose special problems for digestion?
Because they are insoluble in water.
Where is bile produced?
In the liver.
Where is bile stored?
In the gallbladder.
What are the components of the biliary system?
Liver, gallbladder and bile duct, duodenum, ileum, and portal circulation.
Which cells of the liver synthesise bile?
Hepatocytes.
When do hepatocytes of the liver synthesise bile?
Constantly.
What are the components of bile?
Bile salts, cholesterol, phospholipids, bile pigments, ions, and water.
What are stimuli for secretion of bile from gallbladder?
In cephalic and gastric phases these are vagovagal reflexes; in intestinal phase this is CCK (secreted when the chyme reaches the small intestine).
What is the result of stimulation of vagovagal reflexes and CCK on the gallbladder?
The contraction of the gallbladder and relaxation of the sphincter of Oddi --> secretion of bile.
What inhibits the emptying of the gallbladder?
Sympathetic nerves.
When the lipid absorption is complete in the small intestine, what happens with the bile that was secreted there previously?
The bile salts are recirculated to the liver via the enterohepatic circulation. In the liver bile acids are taken up by hepatocytes.
Which substances are secreted by small intestine and what are their main functions?
Epithelial cells secrete mucus(protects the mucosa and lubricates intestinal contents),
alkali aqueous secretions (buffer gastric acid),
enterokinase (activation of trypsinogen to trypsin).
What is the structural difference between small and large intestines?
Small intestine use villi and crypts, but large intestine has just crypts.
Fill in missing numbers or words (yes/no).
What are two main functional differences between large and small intestine?
Small intestine does not actively secrete K+, large one does;
small intestine absorbs nutrients, large one does not.
Where of the following the frequency of slow waves are higher: ileum/duodenum/jejunum?
Duodenum (13/min) > jejunum(11/min) > ileum (9/min).
Motility of small intestine is directly controlled by what?
By enteric neurones and hormones.
Motility of large intestine is directly controlled by what?
By enteric neurones (the exception is control of defecation).
Where does the main absorption happen?
In the small intestine. Large intestine only absorbs water and salts.
For how long does the digested food stay in the small intestine?
3-8 hours.
How does the absorption happen in the intestine? (Diffusion, active transport, etc.)
Simple diffusion:
Water
- Water-soluble small molecules
- Fat and lipid-soluble molecules;
- Facilitated transport, Active transport:
- Glucose
- Electrolytes;
Endocytosis: Larger molecules.
Where does the absorption of the vitamin B12 happens?
In the ileum.
How does the absorption of Carbohydrates happen?
Co-transported with Na+.
How does the absorption of proteins happen?
Amino acidd - Co-transported with Na+;
Peptides - Co-transported with H+.
How does the absorption of fats happen?
Formation of mixed micelles with bile and diffusion.