4 - Pancreatic Secretions PPT Flashcards
Secret Pancreatic Ions!
Where on earth is the pancreas located?
Epigastric region behind the stomach
(TRUE/FALSE): The pancreas only produces endocrine hormones.
(FALSE): The pancreas produces both endocrine and exocrine hormones.
The pancreas has ________ and ________ cells that produce endocrine hormones like ________ and ________ that are secreted into the bloodstream to regulate blood sugar levels.
- alpha, beta
- insulin, glucagon
What type of hormone is secreted the most from the pancreas (around 90%)?
Exocrine hormones
What are the goals of exocrine secretions from the pancreas?
To help neutralize acid and digest food within the intestines
What are the divisions of the pancreas called?
Lobules
What are pancreatic units called?
Acinus/acini
What do the ductal cells secrete to help neutralize the acidic stomach contents as they enter the intestines?
Bicarbonate (HCO3-)
Reminder- what should we always think when we see the word “bicarbonate”?
Intercalated ducts merge together, forming an ________ duct which joins together with other ________ ducts to finally drain into the main ________ duct.
- intralobular
- intralobular
- pancreatic
What travels through the length of the pancreas and drains into the duodenum?
The main pancreatic duct
What are some enzymes produced by acinar cells?
- Pancreatic amylase
- Trypsin/Chymotrypsin
- Lipases
What’s the function of pancreatic amylase?
It breaks down carbs
Idea: “Pancreatic amylase c̲r̲u̲s̲h̲e̲s̲ carbs”
What’s the function of trypsin/chymotrypsin?
They break down proteins
Idea: “Trypsins pu̲l̲v̲e̲r̲i̲z̲e̲ proteins”
What’s the function of the lipases?
They break down lipids
Idea: Triple L- “Lipases Liquify Lipids”
An inactive enzyme will have the ending…
… -ogen!
What inactive enzymes can be synthesized from acinar cells?
Proenzymes and zymogens
Why are these enzymes kept in an inactive state?
To prevent self-destruction (essentially preventing them from eating you alive)
What failsafe did our Creator implement to prevent enzymes from doing damage should they become prematurely active?
The enzymes are to be stored in vesicles alongside a protease inhibitor to shut the enzyme down. So cool.
What is trypsinogen?
A zymogen (inactive enzyme) that is released into the pancreatic duct to make its way to the small intestine- it is activated by protease enteropeptidase.
Ductal cell secretions are filled with various ions, including…
- Sodium (Na+)
- Potassium (K+)
- Chloride (Cl-)
- Bicarbonate (HCO3-)
During 𝐡𝐢𝐠𝐡 𝐟𝐥𝐨𝐰 𝐫𝐚𝐭𝐞, which is when food contents are present in the intestines, what are the respective concentrations of HCO3- and Cl-?
𝐇𝐢𝐠𝐡 HCO3- & 𝐥𝐨𝐰 Cl-
During 𝐥𝐨𝐰 𝐟𝐥𝐨𝐰 𝐫𝐚𝐭𝐞, which is when food contents are NOT present in the intestines, what are the respective concentrations of HCO3- and Cl-?
𝐇𝐢𝐠𝐡 Cl- & 𝐥𝐨𝐰 HCO3-
What’re the three phases of pancreatic secretions?
- Cephalic phase
- Gastric phase
- Intestinal phase
What happens during the Cephalic phase?
- Sensory inputs (sight/smell) stimulate the brain
- Brain sends efferent signals via Vagus (CN X) to pancreas
- Vagus releases acetylcholine that causes acinar cells to secrete enzymatic fluid
What happens during the Gastric phase?
- Distention of stomach is sensed by mechanoreceptors
- The afferent info travels via Vagus (CN X) to the brain
- Brain sends efferent signals back to the pancreas to cause acinar cells to produce slightly more fluid
What happens during the Intestinal phase?
Chyme gets sent out; this phase is responsible for over 80% of pancreatic secretions
What is chyme?
Partially digested food and stomach acid.
- Check out this absolutely cursed picture I found
Where does chyme go during the intestinal phase?
The duodenum
What happens to the proteins and lipids within the chyme?
They are broken down into their monomers (make sens rye) by pancreatic enzymes that were produced in the earlier phases
The presence of fatty acids and amino acids (monomers) stimulates what cells in the lining of the duodenum and jejunum?
𝐼 Cells
Once stimulated, these 𝐼 Cells secrete ___________ to act on acinar cells to begin the secretion of digestive enzymes.
Cholecystokinin (CCK)
What else is CCK responsible for?
Gallbladder contraction
(TRUE/FALSE): Chemoreceptors send afferent information via Vagus (CN X) to increase secretions during the intestinal phase.
(TRUE): This does in fact happen- Chemoreceptors DO send afferent information via Vagus (CN X) to increase secretions during the intestinal phase!
What other hormone is secreted during the intestinal phase? Is it:
A - Secretin
B - Ghrelin
C - Testosterone
D - Gooba-gabba
A - Secretin
Good job 👍
What signals to the S cells within the duodenum to release secretin?
The acidity detected
Why do the S cells want to release secretin when high acidity is detected?
Because then the aqueous portion of the pancreatic fluid massively increases, and it just so happens that this aqueous portion contains a crap-ton of bicarbonate (HCO3-) to neutralize that acidic chyme!
When the chyme finally leaves the duodenum and enters the ileum and colon, what peptide inhibits the pancreatic secretions?
Peptide YY from neuroendocrine cells
What, oh what is made by the liver and stored in the gallbladder?
𝓑𝓲𝓵𝓮 <3
What are the functions of bile?
Digestion, absorption of lipids, excretion of various molecules, emulsification
Lipids are hydrophobic, so what does bile need to do?
Bile MUST emulsify and solubilize the fats.
What is bile made up of?
- Bile salts
- Phospholipids
- Cholesterol
- Bilirubin (a bile pigment)
What are the steps to create bilirubin?
- Hemoglobin from RBC is taken up by macrophages
- Macrophages convert heme into biliverdin
- Biliverdin converts to bilirubin via biliverdin reductase
What is bilirubin’s classification once it completes these first three steps?
Unconjugated/indirect
What binds to unconjugated/indirect bilirubin within the blood?
Albumin
What happens after albumin binds to the unconjugated/indirect bilirubin?
Unconjugated/indirect bilirubin is taken up into hepatocytes, where it turns into conjugated/direct bilirubin!
Bilirubin’s conjugation makes it more soluble, which means it can be secreted into…
… BILE!
In the intestines, bacteria hydrolyze the conjugated/direct bilirubin, reducing it to a colorless compound called what?
Urobilinogen
What form of bilirubin gives doodoo its signature brown color?
Stercobilin
What form of bilirubin gives urine its signature yellah color?
Urobilin
How much of bile acids are recycled and how much of them are lost in feces?
- 95% recycled
- 5% lost
What are carbs referred to as?
Saccharides
List our three monosaccharides we can find in our foods.
- Glucose
- Fructose
- Galactose
